Corvette Central is excited to announce that company Founder and CEO Jerry Kohn will be inducted into Bloomington Gold’s Great Hall.  Bloomington Gold, held yearly in the state of Illinois, is one of the premier Corvette gatherings in the USA.

The 1970′s were a time when new Corvette parts were scarce and most Corvette owners spent time sifting through used parts at swap meets. It was then that Kohn, a tool & die specialist and Corvette enthusiast from Michigan, was searching out much needed parts for a 1958 Corvette. He soon found that the parts he needed were either unavailable, of poor quality or overpriced.  He recognized the opportunity to create his first reproduction parts: grille teeth for 1953-1960 Corvettes. In October of 1974, he took his first sets of reproduction grille teeth to a Corvette show in Illinois. Soon, other Corvette owners were asking for grille teeth and Jerry began making sets for fellow restorers. The need for reproduction Corvette parts greatly exceeded Jerry’s expectations, and so Corvette Central was born.  Today, Corvette Central manufactures over 3,000 parts at its facility in Sawyer, Michigan, and has over 50,000 different Corvette parts and accessories to choose from.

According to Bloomington Gold’s announcement: “The 50 people and 50 cars that played the most significant roles in the Corvette phenomenon are being selected for introduction into the Great Hall between 2010-2014.  Each year 10 people and 10 Corvettes are featured at the annual Bloomington Gold event in June. ”

For more information on Corvette Central, please visit www.corvettecentral.com

By Chris Petris

Petris Enterprises

Do you have a C5 with a horn that no longer functions, or worse, one that blows continuously? Your local GM dealership will probably provide you with a quote of $900+ for an airbag assembly to remedy the problem. That’s a lot of money to fix a horn!

Testing for a malfunctioning horn switch begins at the underhood electrical center. Locate and remove the horn relay for circuit testing. A 12 volt test light will be used for testing. You cannot damage any of the horn components (including the horn switch in the air bag) when using a test light in this manner, whether the test lead is on battery power or ground. Connect your test light lead to a good ground (the battery is the best place). The horn relay has four terminals; you should find that two of the four horn relay socket terminals have a bright light (battery voltage) during testing. Now the test light lead is placed on the battery’s positive terminal for the next test. When probing the remaining two horn relay socket terminals, you should find one that will illuminate the test light when the horn button is pushed. This is the relay control wiring coming from the horn switch. If you cannot get the test light to illuminate when pushing on the horn button in one of the two remaining socket terminals, the horn switch is the most likely problem. The remaining socket terminal should light dimly as it feeds low voltage current to the horns themselves. If the socket terminal does not illuminate your test light dimly, the horns have an open circuit (horns are bad).

Keep in mind that the wiring from the horn switch to the relay could have an open circuit which will require you to access the horn wiring below the dash. You would have to locate connector C209 at the steering column. C209 has 23 cavities; you would need to find the black wire in position V. When the horn switch is pushed a test light connected to battery power should light up with the test light probe in connector position V. We have also found the connector under the airbag for the horn switch broken with the wire hanging loose. In most cases further steering column work is required to replace the cancel cam that the horn switch wiring locks into.

The horn switch itself is a high tech membrane switch that consists of two thin plastic sheets with what appears to be a copper viscous paste. Over time the copper viscous fluid shorts out, the horn switch contacts close, and then the horn keeps sounding. Another common problem is the membrane switch will not close the circuit and the horn will not blow. Corvette Central has the correct replacement switch ready to install with the required wire leads. Corvette Central’s item number 565100 is at a considerably lower cost than the complete air bag assembly. The tricky part is that the membrane switch is part of the air bag assembly sandwiched between the cover and the air bag itself.

IMPORTANT SAFETY TIPS

• The air bag system is powered up for an extended period of time after the battery is disconnected with a Sensing Diagnostic Module (SDM). Even though you may have disconnected the battery, air bag deployment is possible up to 10 minutes after the battery has been disconnected.
• Static electricity can also deploy the air bag. Replacing the switch on a crisp, dry, cold morning can be dangerous. GM uses a shorting bar on the air bag connector to alleviate the possibility of static electricity deployment. Make sure the air bag assembly is on a non-conductive surface and avoid the connector terminals.
• GM suggests that the ignition key be removed as well as fuse number 16 from the fuse panel for SDM power. The panel below the steering column is removed next to access the air bag yellow two-wire connector. All air bag wiring has a yellow sheath to denote it is part of the Supplementsl Inflatable Restraint System (SIRS). Remove the connector lock and disconnect the two-wire connector.
• Do not work directly over the air bag at any time. Set the assembly aside in an open area once the cover is removed.       
• Extreme caution must be taken any time an air bag is handled. Make sure that you have grounded your hands on a metal object to release any static electricity before handling the assembly.

The tricky part is that the horn cover has to be removed from the air bag so the switch can be installed into the cover. We removed the air bag assembly then brought the cover over to our bench. First, the air bag fascia cover must be removed, and then the switch is replaced. Admittedly, it is a bit unnerving to see the air bag folded up in place when the horn fascia cover is removed. Installing the switch into the cover was not too difficult with some careful plastic trimming. The membrane switch was slid into place and the cover reassembled.

Over time, C5 Corvette horn switches will fail.  If you have any trepidation at all about working with an air bag, it is recommended that you consult a professional.

Here we are testing the horn relay connector terminals. This is the correct terminal to test the horn membrane switch. Our test light illuminates with the test light lead on the battery positive post and the relay terminal as shown. The two terminals to the left of the terminal tested should have battery voltage.

The airbag assembly comes off after removing the two T-40 Torx screws from the backside of the steering wheel. The T-40 bit must be at least an inch and a half long to reach the screws.

The yellow connector has to be removed by pulling the connector straight out. These two gold pins inside the air bag module should be covered with tape to prevent accidental static electricity from activating the air bag.

Now the red horn wire connector is twisted counterclockwise to release the connector. Care must be used when removing and installing this connector where it locks into the turn signal cancel cam. The cancel cam has a small plastic leaf that can be easily broken.

Four ten-millimeter nuts are removed to release the horn cover retainer.

 Corvette Central sells this horn contact membrane for C5 Corvettes.  Item # 565100.

We trim the rubber away that was heat sealed to retain the membrane switch backing plates. The rubber from both backing plates is trimmed on the inside to slip the switch out.

The backing plates are lifted up off the rubber on both sides. Care must be taken to avoid breaking the backing plates.

The new membrane switch is sandwiched under the white plastic retainer and some plastic welding secures the retainer back in place.

The cover is ready for installation on the air bag assembly. The air bag can deploy if static electricity or any electrical charge touches the yellow connector so be sure to avoid and cover the connector until it is ready for installation. This should not be done by a novice; the airbag must be respected to avoid injury.

If you’re gonna pound on an LS engine that features OE rocker arms, you need to perform this simple aftermarket trunion/bearing upgrade!

In the process of building any LS engine, if you plan to use OE rocker arms (whether re-using originals or using new OE rockers), you should be aware of the critical need to perform an upgrade to the rocker arms. Specifically, the OE trunions and trunion bearings should be replaced with an aftermarket upgrade kit.

There’s nothing wrong with GM’s rocker arm design. It’s lightweight and stiff, and the OE rocker arms are strong enough to withstand most applications. However, in high RPM situations and when used with high valve spring pressures, the factory cageless trunion needle bearings may tend to begin walking out of the rocker arm’s pivot trunion bore, resulting in individual needle bearings scattering throughout the engine. Obviously, this isn’t good for either the rockers (no bearings) or the rest of the engine. If, during an oil change, you find small needle bearings in the oil or stuck to the magnetic drain plug, this is evidence of rocker arm needle bearings that have worked their way out of the rocker(s). This condition, although possible in any daily driver, is more prone to occur if the engine is operated at frequently high engine speed, and/or if high valve spring pressures are used (as when changing over to a hotter cam that includes higher-rate springs). Knowing that this possibility exists, the best course of action is to address the issue before it becomes a problem, either by changing to high quality aftermarket performance full-roller rockers, or by upgrading the original rocker arms.

Comp Cams, as an example, offers a trunion bearing upgrade kit, part number 13702-KIT. This kit, applicable to LS1/LS2/LS3/LS6/LS7 OE rockers, includes new trunions, new caged and pre-lubed bearing assemblies, circlips and rocker arm mounting socket head cap screws (along with two thick installation-assist washers). The new trunions feature extended tips with circlip grooves. Instead of the bearing housings relying on a press fit, the additional circlips serve to prevent possible bearing assembly walk-out. The new trunions and bearings are also made of higher quality materials and are designed to withstand higher RPM and high spring pressures.

For performance use, get rid of the OE powdered metal trunion and the cheap uncaged bearings in favor of a durable aftermarket trunion kit upgrade. OE setup shown here.

Comp Cams offers P/N 13702-KIT, a must-have upgrade for OE rocker durability.

Comp’s fully-caged roller bearings are a sensible upgrade from the uncaged OE bearing assembly.

The Comp upgrade kit features high-strength steel trunions, caghed bearings and peace-of-mind circlips. There’s no way that this setup will ever allow bearing needles to fall out.

Before performing the upgrade, inspect your OE rockers. If the pushrod cups appear worn, such as this example, trash the rocker.

Shown here are two LS OE rockers. The rocker pushrod cup on the left is severely worn, as compared to the rocker’s cup on the right, which shows no wear damage.

The Comp upgrade kit also includes a pair of thick steel washers which are used during the press-fit of the new bearings.

The upgraded Comp trunions are a tad longer than the OE trunions, featuring circlip grooves at each end.

This photo is for illustrative purposes. Here, a pair of bearings are placed onto the new trunion. Notice the circlip groove at each end. In addition to the interference fit of the bearing cages into the rocker arm, the additional security of circlips insures positive capture of the bearing cages.

During assembly, the kit’s washers provide positive stops during the press-in of the bearings.

Comp’s upgrade kit replaces the cageless, loose OEM needle bearings and powdered metal trunions with premium 8620 steel alloy trunions and fully-caged roller bearings for vastly-improved durability. According to Comp Cams, this rocker arm upgrade has been tested and performance-proven for several years in the NASCAR GM LS spec engine series.

If you intend to “play” with your LS engine and you plan to use OE rockers, upgrading the trunions is a MUST-DO modification to avoid potentially catastrophic engine damage.

Trunion Upgrade Procedure

Performing this retro-fit upgrade is relatively simple, requiring no modifications to the rocker arm. You’ll need a punch, a press or vise, an appropriate-size socket and snap ring pliers. Specialty press kits are also available to ease the job.

Using a punch and an appropriate-size socket or steel tube to cradle the rocker arm, gently tap out the existing trunion, being careful notto damage the rocker arm. The factory trunion will unseat. Be sure to push out both sides. Inspect the rocker arm trunion bore and make sure that there are no burrs. By the way, this is a good time to clean the rocker arm bodies. If you want the rockers to look factory-fresh, clean with solvent, or have them tumble-cleaned with a fine-grit stone, or you can glass bead blast the rockers, but if you blast with fine glass bead, be careful not to dwell any blasting in the trunion bores. Do not run any type of hone or reamer in the trunion bores. If trunion bores appear to be damaged, replace the rocker arm.

Using an appropriate-size driver (steel tube or socket), push the bearings and trunion out of the rocker. A specialty fixture on a bench vise is shown here, but a hydraulic press is commonly used.

Push the old trunion completely out of the rocker along with both OE bearings (rocker out of vise here for viewing only).

Here the OE trunion and bearings have been removed from a rocker. Notice the small needle bearings? How’d you like to have a bunch of these floating through your engine?

Using appropriate size drivers, push a new caged bearing into one side of the rocker.

Once one bearing is in place, insert a new trunion (I suggest lubricating the trunion first).

Insert the new trunion so that one end engages the newly-installed bearing.

With the new trunion in place, insert the next bearing onto the trunion (this slips on). Make sure that all bearings are installed with the stamped lettering side facing outward!

Here the second bearing is in place on the trunion.

Place one of the kit’s washers over the exposed end of the trunion, against the outer face of the new bearing.

Using a press (or in this case a vice with a specialty fixture to secure the opposite side), press the bearing into the rocker, so that the outer face of the bearing is flush with the outer surface of the rocker body.

Here, both bearings have been press-fit into place. Notice the exposed circlip grooves on each end of the trunion.

Using snap ring pliers, install one circlip into each end of the trunion. Rotate the trunion and inspect to verify that each circlip is fully seated.

This closeup shows a circlip installed. Notice the small stamped letters on the outer surface of the bearing cage. Remember, the stamped letters of each bearing must face outward.

This rocker is done and ready for high performance use. Comp’s bearings are fully caged and of the highest quality, and the machined steel trunions offer much greater strength as compared to the powder metal OE trunions. Nothing against powdered metal, but 8620 steel is stronger and is more suited for higher valve springs pressures.

This overhead view shows a fully assembled rocker with Comp’s trunion upgrade.Notice that one side of the trunion mounting hole is recessed (countersunk with a flat surface). This recessed side of the hole must face upward during rocker installation (the opposite side of the trunion is round, to rotate on the rocker stanchion).

Instead of using the OE hex head rocker mounting bolts, Comp provides a full set of socket head cap screws.

The cap screw head nestles into the trunion hole’s recess. Apply a bit of assembly lube under the screw head before installation, and torque to Comp’s recommendation of 22 ft-lbs.

1. Place the rocker arm body on a press and place a new bearing assembly on top of the rocker in a flat and even position. NOTE: Bearings MUST be installed with the identification letters facing outward on both sides of the rocker arm.

2. Carefully press the bearing into the rocker arm until the outside of the bearing assembly is flush with the rocker arm body.

3. Once the first bearing has been installed, flip the rocker arm over. Apply a coating of assembly lube or engine oil to the new trunion and install the new trunion. This will serve to locate the opposite bearing.

4. Place the kit’s installation washer under the rocker arm body. Make certain that the trunion fits through the center of the installation washer.

5. Place the rocker arm (along with trunion and washer) onto the press, with the washer on the bottom.

6. Place the next bearing on top of the rocker (flat and even), with the bearing identification letters facing outward.

7. Next, place the second assembly washer on top of the bearing (the trunion will pass through the washer ID). Press the bearing into the rocker until flush with the rocker body.

8. Using a pair of snap ring pliers, install one snap ring to each side of the trunion. Repeat this process for all rocker arms.

9. Install the upgraded rocker arms to the cylinder heads using the new socket head cap screws supplied in the kit. Be sure to rotate the trunion so that the flat recess side of the trunion’s center hole faces upward (the socket head cap screw must seat against this recessed flat side of the hole). Tighten the cap screw to a value of 22 ft-lbs, following the OE installation procedure.

We installed our trunion upgrade kit using a custom installer kit, using a bench vise instead of a hydraulic press, but either method is acceptable. Just remember that you should always smoothly draw the old trunions out and draw the new bearings in. Do not try to bang the old trunions out or attempt to install the new bearings with a hammer. Leave your hammer in the toolbox.

http://www.precisionenginetech.com/

CorvetteOnline.com recently published an informative video on installation of these rocker arm trunions.

By Chris Petris

We left off with Split Mod’s engine built and ready for installation; now we are moving on to the transmission, differential and camshaft choices.  We discussed the various options available for the driveline before any engine components were chosen. All too often, camshaft incompatibility with drivetrain components leaves projects in the “garage art” category.  To keep an owner happy, all the driveline components need to be carefully matched for optimum performance.

Fuel economy should be a factor if owners want to frequently driving their finished project. Camshaft technology has come a long way from the early Duntov 30-30 small block camshaft that was the rage in the late sixties. Camshaft lobe duration refers to how long the valve is left open during the intake stroke. There are also terms like lobe separation and centerline that make major differences in engine performance. Camshaft lift concerns the volume of fuel charged air that can be drawn into the cylinder.

Camshaft duration affects both low and high speed engine performance.  Want great low-end throttle response? That will come at the expense of some top-end power.  Likewise, a high-revving performer will suffer at lower RPMs.  Today camshaft designers and builders like Comp Cams have made vast improvements on overall engine performance by spending countless hours testing and tweaking each camshaft profile.

Other factors besides transmission and differential gear ratios play into the selection of the correct camshaft. Engine intake, exhaust, and fuel control also affect camshaft selection. For instance, GM originally employed batch fired fuel injectors that were not happy with long duration camshafts.  We must factor in fuel control system, intake, exhaust, transmission, and differential ratios. The large plenum SuperJet Dropped Top intake will help low RPM performance while the FAST fuel control system will be used in bank-to-bank injector control. If we went to sequential fuel injection control the camshaft, duration could be greater.

We definitely wanted a 5-speed overdrive to replace the original 1:1 4-speed transmission.  Keisler Engineering has been working on a better fitting overdrive transmission, so we decided to look into that as our overdrive alternative. Keisler’s 5-speed RS PerfectFit kit comes in two versions for the Midyear Corvette: 400 (400 lbs/ft) and 500 (500 lbs/ft). The most noticeable aesthetic feature is the RS rounded top case to allow it to fit better in the confines of the transmission tunnel. Another plus is the smooth, easy shifting of this latest unit.

Now we can begin to put the puzzle together. Our RS500 transmission choice has a 3.37:1 first gear ratio with a .67:1 overdrive ratio. The steep 3.37:1 first gear will get us moving easily even with a slightly aggressive camshaft profile. Our differential gear ratio can be lower numerically having Split Mod launch well with a compounded first gear ratio of 4.49:1 using a 3.36:1 differential gear set. We can cruise at 76 MPH with our engine barely working at 2200 RPM. We do need to consider our cruising RPM with the camshaft profile for efficient fuel economy and overall engine performance under load.

With all our ratio numbers figured out, camshaft selection can take place. If you have plans for transmission or differential changes in the future, remember to consider the camshaft effect on overall engine performance.  Comp Cams has an online service available (CAMQUEST.com) to get the quickest camshaft recommendation results. One nice feature is their desktop type dynamometer feature to give you an idea what the results will be after adding the required info.

We consulted their camshaft tech line and asked for the best possible camshaft. After crunching the numbers, they came up with camshaft CS XR276HR-10 as the best possible all-around choice. We wanted a slightly noticeable choppy idle (after all this is not a Cadillac) with excellent torque at our 2200 cruising RPM. The 276 degree intake duration camshaft should make 320 plus foot pounds of torque at 2200-2500RPM. Peak torque of 364 foot pounds will come in at 4500RPM, the constant rise in torque will mean less gear shifting once the 5 speed is put into overdrive. Our 367 peak horsepower comes in at 6000RPM making for smooth linear power band.

In first gear, the 3.37:1 Keisler RS500 with almost 200 foot pounds of torque off idle will be easy on the clutch; nothing is more aggravating than having to slip the clutch to get rolling as you tease the throttle. All of the above factors should be considered before you make the plunge, whether it is a differential gear set, transmission, or camshaft purchase. Taking some extra time upfront to look at the options available is good for everyone. Corvette Central wants to make sure you have the best possible fit for your project. Changing plans midway can be aggravating; you end up with parts that do not work and possibly cannot be returned.

Our 3.37:1 differential gear with posi-traction came as an assembly from Corvette Central ready to install. GM used two different axle shaft retention systems: U-bolt and machined caps. U-bolts were for low HP and torque applications and machined caps were used for high output engines. A few words of caution are warranted: The machined caps can interfere during axle shaft rotation when the wheels are hanging freely i.e. jacked up or on a lift. Do not try to run the engine and rotate the wheels with them hanging free. U-bolts also come dangerously close to binding as the shafts rotate.

Corvette Central’s Jerry Kohn and I discussed what fasteners to use. We mentioned earlier on that the factory pieces corrode quickly even when not subjected to harsh conditions. We used Totally Stainless fasteners on every possible location to thwart the inevitable corrosion we would encounter. We touched base on them earlier and to date have used stainless fasteners throughout the project. We have also painted every piece we have installed to prevent corrosion on the components if possible.  Before the body is set on the chassis, we will be performing a quick fit check of the exhaust system. We are using a Vette Brakes and Products Smart Strut assembly that can create an interference issue when using the correct Midyear exhaust pipe routing. Corvette Central’s intimate knowledge of how all of the 1963-1982 systems are routed made the task easy. They suggested we use later rear pipes from their ‘68-‘72 in-house formed exhaust pipes which fit perfectly without any modifications. Early 1963s had tool pockets formed in the floor pans that could possibly interfere with the later style close to center pipes. We had no problem with clearance because our ‘63s body is sitting on body cushions moving the body up away from the exhaust. Once we feel comfortable with the exhaust system fit we remove the mufflers to prevent body damage. The mufflers tuck up inside the rear fenders making them possible rub points as the body lowers.

Please follow along as we show some of the finer points of the differential assembly. Although we used a complete differential assembly from Corvette Central for Split Mod, they have all the pieces necessary for a complete overhaul of your differential. The disassembly is straightforward with a couple of very important things to remember and catalog.

TIPS:

Record the ring gear to pinion backlash before disassembling any components. This pertains to using the original ring and pinion set when changing bearings. If the same side bearing shims are reused, the backlash should stay the same, if not, chances are the pinion bearings have different dimensions than the removed bearings. This would affect backlash.  Worse yet, differential noise could occur from the change in pinion depth.

Tag the side bearing shims so they can be put back where they came from. Make sure you remember what position the differential housing was in (laying on the top or bottom of the housing in respect to how it sits in the vehicle) during disassembly.

Mark the bearing caps so they are installed in the same location. Each housing is different and the centerline of the bearing is not always the split line of the bearing cap. For the best fit the caps should stay on their respective sides.

Gear oil should be changed every 2 years regardless of mileage. Corvettes that sit for prolonged periods of time will have condensation in the lube. Corvettes that are driven frequently will have metal particles in the lube from the constant rubbing of the metallic posi-traction clutch plates. The metallic slurry courses through the bearings, causing wear. Always use posi-traction lube additive with the gear oil. Popping or chattering from the differential during turning indicates low lube additive in the fluid lubing the posi-traction clutch plates.

Corvette Central has all the parts and lubricants to keep your 1963-1982 differential going for the long haul.

Photos

Broken posi-traction clutch discs can be expected after 33 plus years of operation. These metallic clutch plates rub against each other during cornering; even slight deviations from straight-line driving cause the plates to move eventually wearing them. Two points to consider here: we would have not known how badly the clutch plates were worn unless we totally overhauled the differential and servicing the differential is important to drain out the inevitable metallic slurry that builds up in the differential case.

We are installing the new clutch pack with pinion drive gear into the differential ring gear case. Corvette Central has the correct plate kit consisting of the friction plates and case reinforcements; all you add is a copious coating of differential lube before installing. Eaton installed washers on the clutch plates to set clutch pre-load and they must be installed in the same manner and amount. Be sure to record the position during disassembly.

Now the fun begins. The pinion idlers are installed next placing them one at a time into the case. The first idler can be rotated around to the inside of the case easily.

We rotate the pinion drive gears until the first idler is approximately 180 degrees from the large opening in the case.

Things get interesting now because the pinion idler washers fit tightly between the gear and case. Like installing the first idler, the first washer goes in with slight coercion. Do not tap on the washers with a hammer because they bend, crack, and become distorted.

The second washer is installed after we set the case up in the vise with a yoke to allow us to turn the pinion gears. The bolt placed in one of the ring gear retention holes allows us to use a screwdriver to rotate the case.

We install the second washer then work the case back and forth on the yoke while pushing the washer into place. Once the washer is in place the gears are lined up for pinion pin installation.

The pinion shaft is installed for a trial fit before we move on to clutch spring plate installation. Now is the time to know if the shaft will go through the gears easily.

We use safety wire to hold the clutch spring/plate assembly together for installation in the case. The springs and plates are captured in a bench vise to compress the springs fully to install the safety wire. Once the plates are in place use side cutters to cut the wires. Make sure to remove all the cut wire before proceeding.

The shaft can now be installed for the final time. The shaft retaining screw is installed with a toothed washer to prevent it from coming loose. Torque the ¼-20 screw to 110 lbs/in.

The ring gear is installed and then torqued per the manufacturer’s specifications. Before the ring gear is placed on the case check both the ring gear and case for surface imperfections. If necessary remove any high spots with a sharpening stone.

New case bearings are installed, making sure they sit flush against the case. Applying light oil to the bearing’s surface where it sits on the case helps ease bearing installation. Heat also eases installation, but be careful because it is difficult to hold onto the bearing while tapping it onto the case.

Our cleaned case receives new inner and outer pinion bearing races. This inner race is difficult to install squarely due to the depth in the case. Check the bearing race for even installation frequently as it is seated into the case’s bore.

This outer bearing race has been installed. It is very important to make sure the race is installed squarely and seated fully in the bore. If either race is not seated fully pinion bearing preload and pinion depth will change as the differential heat cycles.

The pinion depth is adjusted by these shims under the inner pinion bearing. There are a few ways to determine pinion shim requirements. Trial and error is one method which requires multiple removals of the inner pinion bearing each time a shim change is made or the use of a pinion depth gauge. The pinion depth gauge is used to determine where the ring and pinion manufacturer wants the pinion to set after the machining process.

This gear set wants the rear face of the pinion to be 2.480 from the case’s bearing centerline. The set up tool is expensive for just one time use. Most single gear sets are installed using the trial and error method. You can start with a .030 shim to get close and then tweak the pattern from there.

We use a piece of tubing large enough to fit over the pinion while fitting closely on the bearing’s inner race. Inner pinion bearings will just about fall onto the pinion when heat is applied (we’re talking heat gun heat, not cutting torch). Light oil should also be used to lube the bearing surfaces during application when heat is not used.

The inner pinion bearing was lubed and the assembly installed, then the lubed outer bearing is pushed onto the pinion. The outer pinion should fit snugly and require some force to tap it onto the pinion. Used pinions and bearings usually come off easily which can cause pinion seal leaks as a result of the sloppy fit.

We do not install the crush sleeve until we have the correct ring gear pattern; the yoke is installed then tightened. When we tighten the yoke, we apply enough force to require effort turning the yoke. This will help during the process of ring gear pattern checking.

Our first test will be ring and pinion backlash. During disassembly it is always a good practice to notate where the shims came from and keep them in the same stack and position for assembly. If the pinion shim we selected is close to the previous shim thickness we install the side bearing shims in the same stack and position as before. We try to maintain .008-.010 backlash before checking the ring gear pattern. The case side bearings have shims that set backlash; these at least do not require bearing removal when changing. When you install the case for the first time make sure the ring gear has some backlash before tightening the caps. Check for backlash as you tighten the caps and if the gear locks up, stop and change the shims to avoid gear damage.

Time for interpretation of the ring gear pattern. A gear pattern checking compound is included with gear sets to assure correct gear contact. Here we have an ideal drive side pattern in the center of the gear with contact top to bottom.

The coast side of the ring gear is another story. The pattern is close to the toe of the gear showing us that a thicker pinion shim is required. If the pattern was close to the heel of the gear (outside) we need a thinner shim. We change the shims in .004-.005 increments to make a significant change as in this case. Backlash is correct because of the centered pattern. If the pattern was at the top of the teeth we would need to decrease backlash. If the contact was closer to the root of the gear we would have to increase backlash. Typically .008-.010 backlash results in proper patterns.

Once the pinion depth is correct we install the yoke support bearings from the Corvette Central overhaul kit and then we carefully clean the seal area with brake cleaner.

The yoke seal surfaces are also cleaned with brake cleaner.

This is why we clean the seal surfaces. Permatex Aviation sealer is applied to the seal surfaces.

We use a small hammer to tap the seal into the differential housing. We tap around the outside of the seal to avoid denting or distorting the inner surface of the seal.

Now the pinion crush sleeve is installed onto our new pinion after we know the pinion shim is correct. There are two crush sleeves available: aftermarket and GM. Most aftermarket crush sleeves require much less effort to collapse than the GM pieces. When we use the GM crush sleeves a 6-foot long bar is required and a special holding tool we made is used to hang onto the yoke during the process. Ask for the easy crush sleeve unless you have the tools required for this major operation.

TIP: Many times the pinion seal is blamed for leaking when the bearings are worn and fitting loosely on the pinion. When the seal is replaced the pinion nut is tightened down which can upset the crush sleeve and the bearing preload. The majority of pinion seal leaks are not solved until the pinion seal, outer pinion bearing, bearing race, and crush sleeve are installed.

We cleaned the seal and housing surfaces and then applied our sealer to the pinion seal. Over time the differential housing sealing surfaces get gouged and scratched from careless seal removal. Applying sealer fills the voids and keeps the lubricant where it belongs.

Another common seal installation problem is dry installation. We apply transmission assembly lube (Vaseline) to the seal surfaces to avoid dry start-up of the yoke in the seal. Oil works well also to make sure the seal starts out lubricated.

Our yoke washer receives a bead of high temp silicone to prevent gear lube from leaking out as it travels out the pinion splines. Some yokes fit tight enough that the lube will not get past the splines and this assures it will not.

We always use a new yoke nut for the final time after the pinion depth is set. The yoke nut is tightened until it requires 20 lbs/in to rotate the pinion yoke. This preloads the bearings for break-in purposes. The yoke should have drag during turning but not so tight that it takes two hands to turn the yoke. All pinion bearings must have lubricant applied before the preload is set. Actually, the bearings should have been lubed when the pinion was first installed to check the pattern.

The carrier is installed with our predetermined side bearing shims. We want the shims to fit snugly in the housing and require some effort to install. This also sets bearing pre-load. Replacement shims are easier to install and can be tapped in place without damage. The original GM shims are very hard and can break if they are hammered into place.

Lubing the yoke bearings and seals is next before the yokes go in. The yokes are then installed with new snap-ring clips.

At Petris Enterprises, we drill and tap the 1963-1979 differential housings for a discreet, much-needed drain to allow for periodic draining of the gear oil. We assembled a kit to perform the drain installation and it requires the strut rod bracket to be installed for proper positioning.

This is why we installed the strut rod bracket to lay the template into position for center punching the correct area for the hole saw.

When the differential is in the car we first use this hole saw to cut an access hole for the drain plug tap. Our hole saw has an integral stop to prevent drilling into the differential housing. The stop allows the strut bracket to be cut without cutting into the differential housing.

Now the drill is used to open the hole up for the 1/8 NPT thread tap. Note the stop on the drill bit to prevent ring gear damage from drilling too deeply.

After applying lubricant to the cutting teeth our 1/8 NPT pipe tap is installed next. We also have a stop on the tap to prevent running the tap in too deeply. Yes, there are metal shavings generated during the drilling and tapping process. As the fluid drains out the chips flow along with the fluid to keep metal particles out of the differential.

The Petris Enterprises pipe plug is installed, finishing off the drain plug installation. Now the differential can be drained during routine maintenance services. Siphon guns can be used to remove the old fluid, but the worst contamination occurs at the bottom of the housing where all the metal contaminants drop out of the fluid.

When we install the differential cover we coat both sides, the differential housing, and cover with the Permatex Aviation sealer.

Article and photos by Chris Petris

Power steering is a mechanical wonder that many of us often take for granted. For some, it is hard to even remember a time without power steering. Today’s systems are cost effective to manufacture and are very reliable with just basic maintenance. It is likely that these systems will remain in place for several more years despite the pressure to continually increase fuel economy.

The power steering system consists of a reservoir, pump, relief valve, control valve, power cylinder, and high/low pressure hoses. The system is effective because of the pressure differential that is created by the power steering pump. A quick explanation of how power steering works is in order. The reservoir supplies the fluid to the pump, which is driven by the engine via belt. The fluid is pressurized and sent to the control valve and the relief valve. When the steering shaft is turned, the control valve sends fluid to the power cylinder and the power cylinder uses a piston to aid in reducing steering effort.

General Motors did not intend to give the Corvette effortless, Cadillac-like steering. Instead, they opted to design the system to provide steering assistance while offering good feedback and response on the road at speed. While you cannot expect to turn your Corvette in a parking lot with just your fingertips, the steering assist system is a vast improvement over not having power steering at all.

The power steering assist system does have an Achilles heel, however. The hydraulic cylinder shaft seals are subjected to sand, debris, and all of the elements which wear them down and inflict damage. In addition, control valves can wear and, with their multiple fluid connections, leaks are inevitable. Many control valves are replaced due to what appears to be excess play in the ball stud. In order to make a proper diagnosis, however, the engine must be running with fluid pressure. When the engine is running, the ball stud play should subside. If not, control valve replacement is necessary.

Many times the control valve is also blamed for excess steering play when indeed the steering coupler is worn. Steering couplers are comprised of a rubber disc sandwiched between two metal flanges. The steering couplers job is to eliminate steering wheel vibration. Over time, the rubber deteriorates and causes excess play in the steering wheel. The steering coupler has two pins as a safety precaution to prevent a total loss of steering.

As a result, a cottage industry has formed because of the number of control valves and cylinders in need of replacement. The same items appear on several Corvette generations, making it beneficial to the manufacturers. When it comes time to renovate your power steering system, you have plenty of options. New and remanufactured components are available, as well as hose kits. Unless you are aware of the replacement history of both the power steering cylinder and control valve, it is best to replace both including all of the hoses. The photos that follow will guide you through the process.

This oil soaked, well-worn steering coupler off of a 1969 Corvette created excess play. The best way to check this coupler is to have someone turn the steering wheel within the free play range. Watch for movement in the coupler that does not transmit to the lower flange.

What a difference this correct Corvette Central complete lower flange and coupler assembly (part # 563135) makes. There are rubber disc replacement kits available that can save you some money, but require quite a bit of work to install. Keep in mind that the majority of these vehicles are 40+ years old and the metal flanges do wear, so it is a good idea to replace the entire assembly.

Apply anti-seize to the drag link threads to ease installation and future removal of the power steering control valve.

During the installation of the power steering control valve, it is critical to ensure that the control valve screws on at least 3 or 4 turns with light effort at first. After 3 or 4 turns it will require more effort to seat the valve. Use a ¾“ box end wrench placed on the ball stud to tighten.

The castellated nut is tightened, with an additional half turn until the cotter pin hole is lined up.

In order to ensure your comfort and minimize the risk of inadvertent injury, the cotter pin ends should be bent over and pressed down.

Make sure that you have the machined spot in the drag link lined up with the control valve bolt hole, then install the grade 8 bolt and torque it to 45 ft. lbs.

Install the hydraulic cylinder using the same method as the castellated nut on the power steering control valve to tighten it.

At the frame side of the hydraulic cylinder we install a large washer, rubber bushing, and sleeve. Make sure that the sleeve is installed. The sleeve is often omitted, resulting in crushed rubber bushings.

This is the correct installation of the washers, bushings, and castellated nut. The castellated nut is turned down until the washers contact the sleeve, and then an additional quarter turn is applied to line up the cotter pin hole.

We find that it is easier to install the hose at the power steering pump before the power steering pump control valve.

Again, it is easiest to install the power steering pressure hose onto the control valve next. We are using a wide fitting wrench to prevent line nut damage.

Using a fitting wrench, the power steering return hose can be installed now.

The hoses can be tricky to install on the power steering cylinder since they angle outward and slightly upward. Do not use a wrench to tighten these until you start them by hand and secure them with at least 3-4 turns manually.

The cylinder to control valve hose is installed at the control valve. These hoses must crisscross each other or your power steering will be non-existent.

After the installation has been completed add chassis grease, if required, using a grease gun and a maximum of 3 pumps. Check with your control valve supplier to verify whether or not greasing is necessary.

The small screwdriver indicates a possible friction point where the control valve hoses will hit the cylinder mount. Before starting the engine, move the wheels right to left and left to right throughout the full range of travel watching the hoses for any possible friction or binding points. Be sure to look at the power steering pressure and return hoses for binding concerns as well.

Upon initial start-up, do not place your arm between the steering wheel spokes. A maladjusted control valve can cause the steering wheel to turn abruptly left or right on its own. We are removing the cap to gain access to the control valve balance adjustment 7/16” nut. This particular 1964 coupe exhibited a pull to the right. Before implicating the control valve, we attempt to adjust the balance.

We place our ¼” ratchet with 7/16” socket on the balance nut; then the engine is started. We adjust the balance nut clockwise until the steering wheel begins to move slightly and then rotate the nut counterclockwise until the steering wheel turns in the opposite direction. This will give us the approximate number of turns required to allow the steering wheel to rotate in both directions. For example, if two clockwise turns were required then one counterclockwise turn would center the valve.

If you would like to enjoy the benefits of power steering on your 1963-1979 Corvette that was not factory equipped with power steering, Corvette Central has kits available to make the conversion.

TIPS

• Be prepared; this is a messy job with multiple lines containing fluid to detach and reattach.
• When you have the hoses disconnected, do not move the wheels or a shower of power steering fluid will ensue.
• Refill the reservoir with power steering fluid as opposed to automatic transmission fluid which is sometimes used. Power steering fluid is specially designed to offer higher heat resistance.
• Power steering systems have a return that constantly shuttles fluid back to the reservoir making bleeding the system unnecessary.
• When first started do not overfill the system. Watch carefully because once the engine is running the fluid level will drop. Rotate the steering wheel back and forth 3-4 times with the engine running. Shut off the engine, open the power steering reservoir fill cap, and allow the air to escape the fluid. After 10 minutes, check the fluid level again and if necessary add more fluid.

PARTS

562330                 ’63 – ’82 New Power Steering Cylinder                   $139.95

562336                  ’63 – ’82 New Power Steering Control Valve        $199.00

562355                  ’63 – ’82 Rebuilt Power Steering Cylinder              $99.95

562350                  ’63 – ’82 Rebuilt Power Steering Control Valve   $99.00

562209                  Redline Power Steering Fluid (Quart)                      $11.95

Corvette Central has a variety of hose kits and complete kits with hoses, valves, cylinders, in your preferred configuration of new/remanufactured components.

What follows has been reprinted with permission from Corvette Online. Written by Paul Huizenga

Welcome back to the second and final part of our series on upgrading Project Y2k, our in-house 2000 Corvette, with the help of Corvette Central Performance and their Stage 1-4 kits for the C5. In part one, we installed the Stage 1 and Stage 2 kits, which are comprised of bolt-on intake and exhaust upgrades, along with a flash tuner to maximize the power gains from the hardware improvements.

The stock car’s 317.79 rear wheel horsepower and 334 pound feet on our Dynojet chassis dynomometer netted an eighth-mile time of 8.751 at 80.67. With Stage 1 and 2 installed at the end of Part 1, we had picked up an additional 23 horsepower and 9 pound-feet, and had a new timeslip showing 8.616 at 81.97. That’s not bad for basic bolt-ons and a few hours’ work, but we were eager to move on to Stage 3 and 4 and see how much farther we could go with Project Y2k.

As with Stage 1 and 2, the Corvette Central Performance Stage 3 and Stage 4 kits are designed to give a turn-key upgrade path for 1997-2004 Corvettes, broken into logical chunks. Per Corvette Central’s Matt Gessler, “We want to eliminate the guesswork for late model Corvette owners who are searching for increased performance.” The C5 staged upgrade packages are just the beginning for Corvette Central Performance; “The initial focus was for the C5 Corvette,” Gessler explains. “It really hits the ‘sweet spot’ for affordability and performance at this moment. But we also realize that there are plenty of C4 Corvettes that see track duty, and there seems to be no performance limit for the C6. We continue to source the best performance products available for these cars.”

Talk is Cheap

As with our previous installment, we will be putting Y2k on the rollers after each stage, then taking the Corvette back to the dragstrip to measure our improvements in the real world. Our baseline going in to Stage 3 was 340.59 horsepower and 343 pound-feet of torque at the rear wheels – very healthy numbers for a decade-old LS1 with a few mods, but we were excited to see what the serious speed parts provided by Corvette Central Performance could add to the bottom line.

Stage 3: Goodbye Logs, Hello Long Tubes

The Corsa mufflers we installed in Stage 2 sound great, look awesome, and helped us pick up a few more ponies, but the rest of the stock exhaust plumbing was still in place. Corvette Central Performance’s Stage 3 kit remedies that situation with some of the best long-tube Corvette pipes on the market from Kooks Custom Headers with a matching X-pipe and mid-pipes, plus an SLP underdrive pulley and COMP billet tensioner.

Like the Stage 1 kit, there are two different part numbers available from Corvette Central Performance, depending on what year C5 you have. PN 305462 covers 1997-2000 cars, while 305488 takes care of the 2001-2004 Corvette. The main difference lies in the position of the passenger-side air injection port on the headers, which changed between the 2000-2001 model years.

The stock C5 exhaust manifolds aren’t the worst thing in the world, but they’re clearly designed for packaging convenience rather than all-out performance. They’re also as ugly as second-hand sin.

Our new headers, X-pipe, and mid pipe from Kooks, on the other hand, are works of art in stainless steel.

The headers supplied in Corvette Central Performance’s Stage 3 package are Kooks’ 1 3/4-inch primary design, with 3-inch collectors and provisions for air injection and the primary oxygen sensors. The X-pipe transitions from 3 inches to 2.5, and has bungs for the stock secondary oxygen sensors, as well as an additional capped bung for an aftermarket wideband unit – a thoughtful touch.

We started Stage 3 by pulling the stock H-pipe, then unbolting and removing the stock exhaust manifolds.

The stock H-pipe, compared to the uncatted Kooks X-pipe. Guess which is which…

A side by side comparison of the Kooks’ header and the stock manifold shows how much of a physical difference there is. Long tube headers usually really wake up LS engines, and we were hoping ours would be no exception.

We’ll be honest – even using Kooks’ instructions, long tube header installation is not something that can be accomplished without a little bit of effort. The motor mounts must be unbolted to allow you to rock the engine side to side slightly, and it takes an extra set of hands to hold the engine in position with a persuasion tool while the headers go in.

Once in place, the headers were bolted up using the supplied multilayer gaskets and new hardware.

The long tube headers come together in the center of the car to meet the X-pipe, and feature an internal collector spike to smooth the exhaust flow.

The last step in our exhaust makeover was connecting the headers to the previously installed Corsa Pace Car axle-back exhaust with the Kooks X-pipe and mid-pipes.

Next up for Stage 3 was the SLP underdrive harmonic damper/crank pulley. In order to pull the stock damper, the Corvette’s radiator and steering rack must first be removed…

The SLP damper frees up power by turning the accessories 25% more slowly than the stock pulley, and it also meets SFI specifications for drag race use and safety at high RPM.

The final part of Stage 3 was Comp’s adjustable belt tensioner. Like the damper pulley, it features taller sidewalls to help prevent belt loss at high speed, and unlike the stock spring-loaded tensioner, it lets you precisely control just how much tension is on the main accessory belt.

Stage 3 Results

With our new exhaust and pulley installed, we were right back on the Dynojet to quantify our results. Three pulls later, with the same tune we had loaded for Stage 2, we had an average of 354.15 horsepower and 352.47 pound-feet of torque, a gain of 13.56 horsepower and 9.47 pound feet from our previous high-water mark.

The addition of Kooks headers, X-pipe, midpipes, and the SLP underdrive pulley netted an additional 13.5 horsepower and 9.47 pound-feet to the tires.

Stage 4: A New Bumpstick

Finally, it was time to complete our Corvette Central Performance upgrades with the installation of Stage 4, consisting primarily of a new COMP camshaft, an SLP high-performance oil pump, and supporting hardware to increase reliability and the ability to turn revs. LS1/LS6 engines are well known for their responsiveness to cam swaps, so we were very curious to see what Corvette Central Performance’s choice of specs would do, both in terms of power to the wheels and day-to-day drivability.

The cam provided in the Stage 4 kit is a COMP XR275HR grind, part of the XFI RPM High Lift hydraulic roller family. COMP describes it as a “great street/strip camshaft for midrange and high RPM power” and notes that computer modifications are required. We like a nice, lopey cam, but looking at the lift and duration numbers, we wondered if we were getting ourselves into a Corvette that idled with a little more wiggle than we would like…

COMP XR275HR Vitals:

• Gross lift (intake/exhaust) – .566/.568
• Duration at .050 – 222/224
• Lobe Separation Angle: 112.0 degrees

The heart of Stage 4 is COMP’s XR275HR cam, and Corvette Central Performance also provides matching COMP valvesprings, pushrods, and titanium retainers.

SLP’s high performance oil pump is ported on both the inlet and outlet sides, blueprinted, and given a unique serial number. SLP provides an optional bypass spring that raises operating oil pressure by 5 PSI, which we installed before putting on the pump.

Another important upgrade is switching to the newer factory LS7-style timing chain (top). Just by looking at it you can see that the side plates are far more robust than the stock LS1 chain.

Because of how the LS engine is designed, the lifters are not accessible without removing the cylinder heads. Once the rocker arms and pushrods are removed, you’ll need to have some way to keep the lifters pulled up out of the way during the swap. One way is to use “pencil” magnets through the pushrod holes, or you can do like we did and spin the old cam to knock them up into the top of their bores, then use retaining rods through the oil galleries to keep them there.

A side-by-side look at the stock cam (right) versus the new COMP cam shows there’s a noticeable visual difference in lobe profiles.

Properly pre-lubed, the new camshaft goes in…

With the cam installed, it was time to swap out our valvesprings. An “air hold” keeps the valves seated while Sean removes the old springs and retainers, and replaces them with the new COMP pieces.

The new COMP spring on the right clearly shows its “beehive” shape. Not only do these springs support as much as .625″ lift – the unique shape eliminates harmonic vibration by killing the “resonant frequencies” that are inherent to any straight-wound spring.

COMP’s pushrods are a one-piece, 5/16″ diameter design with a .080″ wall thickness. With a little pre-lube applied, they dropped right in place of the stock pushrods.

The last new component to go on was the SLP oil pump, then we buttoned up the front of the engine, reinstalled the damper, and put the steering rack, radiator, and accessory belt drive back on.

Finally, the work on Project Y2k is complete, and we are ready to find out how we did on our Dynojet chassis dyno…

Stage 4 Results

ProTip: If you are considering doing both the Stage 3 and Stage 4 upgrades, it’s best to do them both at the same time so you only have to remove the steering rack to R&R the harmonic balancer once.

With the wrenching complete, it was time to test our progress, but there was one critical step we needed to accomplish before hitting the rollers again. The factory computer was never programmed to run the engine with this big of a cam, so trying to fire it up with the stock tune is a recipe for disappointment. But there is a solution already in hand – because the flash tuner provided in Stage 1 is also from COMP’s FAST brand, it has provisions to tune for a bigger cam, with three levels of lift and duration beyond stock already stored in its memory. The third and most extreme tune matched our specs, so we reflashed the PCM and fired up the Corvette for the first time with the new bumpstick.

After checking for leaks and admiring the car’s new rumble (and giving the computer a few minutes at idle to settle in and get up to temperature) we headed one slot over in the shop to the Dynojet to see what we had wrought. Three dyno pulls gave us an average of 385.37 horsepower and 372.54 pound feet to the rear wheels, a net gain of 31.22 ponies and 20.07 pounds compared to Stage 3, and a whopping 67.58/38.54 over our stock dyno pulls.

With our Stage 4 work complete, we had a total of 385 horsepower and 352 pound feet to the rear wheels.

Figuring 12-15% loss through the manual transmission and driveline, that means we are making something like 430-440 horsepower at the crank – more than a stock LS3 C6, with fewer cubes (and for less money total, even considering the purchase price of the car and the cost of the Stage 1-4 upgrades.) Of course, to prove the point we needed to make another dragstrip visit, and despite a flagging stock clutch that kept us from launching the car as hard as we might have (this car is no trailer queen, so we made sure we didn’t break it too bad to drive home) we still managed to cut a 12.787 at 11.111 MPH in the quarter mile

Drag Results (Stock / Stage 4 / Net Gain)

• 60-Foot – 2.027 / 1.922 / .105
• 330 – 5.736 / 5.457 / .279
• 1/8 Mile – 8.751 / 8.312 / .439
• MPH – 80.67 / 86.53 / 5.86
• 1000 – 11.335 / 10.764 / .571
• 1/4 Mile – 13.480 / 12.787 / .693
• MPH – 105.43 / 111.11 / 5.68

On the road, our once-ordinary C5 is now something else entirely – if you want to turn heads at every stoplight, that unmistakeable cammed-up lope will certainly do it. The changes don’t appreciably harm the car’s drivability; it starts and putters around town just as well as it did when we bought it, but the new power is just a stab of the throttle away. Ongoing analysis of fuel economy shows we haven’t taken a big hit there either, mostly thanks to the deep double-overdrive transmission that keeps revs and interior noise way down on the highway. Step on the go pedal, though, and the beefed-up LS1 roars to life.

Overall, we’ve achieved exactly what we hoped for with Corvette Central Performance’s Stage 1-4 upgrades, taking what was good about the stock car and making it better. Corvette Central Performance’s upgrade stages for the C5 provide a no-guesswork way to put some extra oomph in your Corvette, and should you decide to go the DIY route, their technical support is there to help guide you every step of the way.

In the coming months, we’ll be continuing on with our improvements to Project Y2k, increasing handling and brake performance to compliment our new-found horsepower, so keep an eye out for future updates…

Article and photos by Chris Petris

You know it will eventually happen: your C3 Corvette’s door hinges wear out and the resulting alignment issues cause a multitude of problems. Sagging, broken seals, road noise, and water leaks to name a few.

Have you ever wondered how many times you have opened and closed the doors on your Corvette, especially the driver’s side door? It has to be thousands of times and the number only increases as a car ages. Owners used to lube their door hinges at every oil change. As oil change intervals increase and busy schedules ensue, these small but important maintenance tasks are often ignored and will eventually lead to door misalignment problems.

Unfortunately, the speedometer cluster has to be removed to allow access to the driver door upper hinge. Luckily, there are plenty of options. Replacing just the hinge bushings and pin is one option, provided the existing pins have not worn through the bushings. If the dash is already out of your car, it makes sense to proceed with replacing the door hinges. If not, to save some aggravation, a pin kit is highly recommended.  Read on as we explain how to assess the condition of your pins and bushings.

The first step is to determine whether or not the hinges must be replaced. You will need to remove the door to properly access the hinges. Trying to replace the pins with the door in place is very difficult and damage usually occurs as a result. Removing the pins is tricky: on the upper hinge, the pin comes very close to the fender edge as it leaves the hinge. There is generally enough room on the driver’s side to sneak it out, but on the passenger side it can be problematic.

On this particular Corvette, the passenger side pin was so close to the fender that tape could not be applied to prevent scratching. It took great care to remove it. Both pins required grinding a flat spot to allow it to pass by the fender. Corvette Central’s door hinge pin set part number is 283100 and includes four pins and eight bushings. The new bushings fit tight in the hinge and the pins made the hinges behave like new again. The original hinge bushings have a thin wall and in some instances the bushings are worn so badly that the hinge itself is damaged. Welding and then machining the worn area is an alternative, but it is tricky to do in confined spaces.  This is why new or rebuilt hinges are available. 

There are other problems that necessitate the installation of a new hinge, like damaged detent rollers (due to a lack of lubrication). The detent spring rollers should rotate as the door is opened or closed to keep your door open as you exit. The rollers have wave washers to prevent them from rattling, so they cannot be rotated by hand, but they should rotate when you grab them with pliers.

Now is the time to lubricate them; first with good penetrant, then grease. White lube is often used for door hinges. Other than the fact you can visually verify it was done, it really does little, if any good. Select something that will get between the rollers and their rotation pin.  Penetrant works best. Lube them often and the rollers will be there virtually forever since they only move a few notches at a time.

This door dolly adapter works great on the floor jack if you do enough door work to justify the cost of owning one. The doors are heavy and awkward to handle; be sure to have someone ready to help when removing the door from the hinges. This ‘73 convertible has manual windows.  Remember to disconnect the power window motor and/or power door lock connectors (if necessary) before removing the door. The procedure is to disconnect the connectors and pull the harness out of the door before loosening the first door hinge bolt.

The hinge pins have a serrated or knurled area at the top to keep them in place. Our air hammer with a pin punch is used to knock the pin upward to release it from the knurled area. When used correctly, air hammers can prevent body damage from out-of-control hammer swings.

The passenger side pin was very close to the fender even after grinding off a section off of the top of the pin. We rotated the pin as it came upward to prevent scratching the door. Hold on to the pin as you move it past the edge of the door.  If the door moves, the pin can crash into the door edge.

Vise grips are used to push the bushing in place. These bushings are tough but brittle. They will break if you decide to beat them in with a hammer.  Exercise care when installing them. The vise grips also push the bushing in squarely to avoid distortion.

Now is the time to install our Corvette Central #283110 door detent spring. We are using our specially modified Craftsman screwdriver. There are specific installation tools available from Corvette Central already configured to make the job easier.  For your convenience, here is an accompanying CC Tech article on hinge installation.

The hinges are back together and ready for door installation. Although it does not happen often, the hinges can wear or bend at their outer stop, allowing the edge of the door to touch the hinge. Ultimately, the outer edge of the door can be damaged from the hinge as it crashes into the hinge body itself. Look for signs of door outer edge damage in the hinge area. If you find any evidence of door hitting the hinge, it needs to be replaced.

We were able to put the door back close to where GM had originally placed it. The original bolt’s washer left a witness mark that we used for our first check of proper door fit.  Use the witness marks to make sure you are going in the right direction.

Now that the hinges are back where they started (thirty seven years ago in the case of this Corvette), it seems that the doors could be reinstalled in their same position; however, that is rarely the case. As the body cushions weaken and the fiberglass stresses, door fit adjustment may be required. You will most likely need to make some adjustments to allow for the best fit. The door hinges have three adjustments: vertical, horizontal, and in/out from the panel surfaces that surround them. If you replace the pins and bushings, you will be able to adjust the horizontal plane only. There will be some slight movement in the vertical position of the door. Vertical adjustment would require accessing the inner portion of the hinge behind the dash cluster.  In most cases, the slight vertical adjustment is usually enough to make the door fit correctly once new pins and bushings are installed.

Remove the door striker pin and check for door-to-door surround opening fit. Once the door fit is optimum, install the striker and move it so that the door closes without dragging on it. After alignment issues are corrected, the doors should fit well without any sagging when the door is opened. Now the real fun begins! Since many windows are  adjusted as the internal components inside the doors deteriorate, realigning windows is next. Another thing to consider is worn outer seal strips and maladjusted inner window bumpers. If you find the outer seal strips are hard or cracked, replace the outside seal strips before adjusting the windows and window bumpers. Corvette Central part numbers 283061 fit coupes, and 283062 fits convertibles. These are original equipment quality pieces. The O.E. strips keep the windows tight and water out. The strips are also an integral part of proper window adjustment since they maintain pressure on the window at the base.

The ‘73 had minor rust and corrosion under the seal strips and garnish moldings. We removed the rust stains with Ospho rust converter treatment. Once the Ospho dried, we applied a coat of quality wax under the strips without polishing off the residue for added protection.

Installing the seal strips can be tricky because they have push-in retainers that must align with their corresponding hole in the door. They must be started with thumb pressure or the retainers can be distorted, or worse yet, the strip itself can be badly bent or creased.

Two screws retain the seal strips. Make sure to use flat head screws (preferably black to keep them from visually sticking out). The screws should lie flat with the flocked material to make sure the glass does not rub against them. Stainless steel screws are ideal.  Always coat the screws with grease to keep them from corroding quickly.

Worn window lift and control components will be an ongoing problem. Now would be a great time to assess the condition of all the window components. The window uses two rollers that travel vertically to control the window’s inward and outward movement. The front roller also controls window fore and aft travel. Loose rollers cause loose windows and will permit the window to change positions each time the window is moved up and down. The tough part of window adjustment is that there are multiple adjustments that affect each other.  This holds especially true when the rollers are worn: each time the window is moved, the fit changes. Position the door glass at the mid to ¾ up position and try moving the glass fore and aft. There will be some movement, but it should not exceed ¼” overall. Excessive fore and aft movement indicates a worn front roller. The door glass should not move up or down at the front or rear either. Worn window regulator rollers are usually the culprit when this occurs.

Another area to check is the fit of the weatherstrip. Door adjustments can alter the fit enough to cause damage or leaks. Before proceeding, we have some photos showing where to look for possible trouble spots. Now would also be a great time to replace any worn or weathered seals. Corvette Central has door weatherstrip available separately or in kit form. Multiple options are available in their 1968-82 print and online catalogs.

The door weatherstripping on our project had been recently replaced, so we adjusted them accordingly. Once the door was adjusted, some minor modifications to the front upper weatherstrip mounting area were required for proper fitment. The upper mounting area was bent, preventing the weatherstrip from seating properly against the door frame.

This is something to watch for: the angled area of the weatherstrip must fit flat on the door to keep correct alignment. We have found that, in some cases, we must trim the angled area of the door itself for the weatherstrip to fit correctly.

Once the weatherstrip is installed, we use a wooden handle to modify the edge that the inner portion of the glass rubs against. In most instances, The inner metal reinforcement is too close to the glass and will cause a scraping noise as the window is raised.

This is what we are most concerned with at the front of the door: the door weatherstrip must slide under the windshield vertical weatherstrip. It is common to find the door weatherstrip rubbing hard on the vertical weatherstrip, which may cause damage or leaks.

Both ends of the weatherstrip are tricky to deal with. The rear corner shown fits around the glass. Open up the weatherstrip attaching hole slightly to fit the end correctly. Once we have the correct location for the weatherstrip, we add a washer to assure a tight fit. Watch the glass as it goes into the rear corner. It is possible to damage the new weatherstrip the very first time the glass is raised.

To complete the door weatherstrip installation, replace the rear deck corner weatherstrips and plastic wedges. Strip caulk was used under the weatherstrips and wedges to make sure they sealed themselves to the body. A thin application that covers the entire underside of the weatherstrip and wedge works best; too much and the pieces will not sit flat.

Our 7/16” socket is on the rear window glass retaining nut. The front window glass retaining nut is accessed through a hole in the inner door frame. The 7/16” screw to the right adjusts the upper door glass limit at the rear of the door.

The front window guide controls the fore and aft position while maintaining the windows inward or outward tilt. The outer screws would tilt the glass in or out contrary to conventional thought. Moving the plate towards you while sitting in the door sill area would move the top of the glass out. The door glass anti-rattle bumper to the left must be adjusted accordingly. If the glass is adjusted out at the top to its maximum position, the bumper would bind on the glass at the window’s upper limit. Fore and aft adjustment is straightforward; exercise care to ease the door closed until you know the glass is not going to crash into the pillar or top.

These two 7/16” screws adjust the windows balance front to back. This controls how the front to rear glass lifts front before the rear, etc. This adjustment is usually not required unless a major change in front or rear upper glass limit has been made. If necessary, adjust the balance track as you watch the window glass roll up. The glass should hit the stops evenly; if not adjust the track until they do.

Carefully scrutinize the situation before you dive in and order parts or make adjustments. Many times adjustments are made and parts are replaced before the underlying problem is found.  Shortly afterwards, the parts that were replaced end up failing because the root cause still exists. Stay calm, take your time, and walk away if your patience is limited. It is quite amazing how well these Shark Corvettes can be sealed up if care is taken while making adjustments. The really great thing is that once the doors are hung properly and the windows are sealed, you can enjoy the drive that much more!

Corvette Central has all the components required for a complete restoration of your doors and door glass if necessary.

Seal strips

Door weatherstrips

Rear deck wedges

Rear deck weatherstrips

Article courtesy of GS Creations, LLC

Tools Needed:

OROR

1. To remove the front OEM side makers, turn wheel all the way to allow access to the fender liner screws.
2. For Years 2005-2007 Remove the 5 screws holding the fender cover on. To remove the 5 screws you will need a Torx T15 bit as shown below or a small flat head screw driver. (For 2008+ you will have the little expansion type pins. There will be a round center “pin” which sits inside a larger expanding base. You can slide a small screwdriver or diagonal cutting pliers under the top of the center pin where those two little indentations are. The center pin will pop up so you can pull it out, and then the base will come right out.) Then you will be able to pull the fender cover out a bit and reach your arm inside the bumper, pinch the clips together and push out on the side marker to pop it out.
3. Remove the light attached by wire by twisting it out.
4. Put the light in your new clear side marker housings and twist in. If you are replacing the stock bulb with our LED’s please be sure to turn the lights on before you put everything back together to test you have it in correct. If it doesn’t light up take the new led out and turn it around. They will only light up if installed one way.
5. Pop your new clear side marker into place and replace the 5 screws you just removed.

What follows has been reprinted with permission from Corvette Online. Written by Lindsey Fisher.

Corvette Central part # 575042

The latest and greatest Corvette coilovers have arrived. Offered by Pfadt, the new feather-light, single-adjustable, coilovers have a new design offering many revolutionary components and benefits. If you want the latest technology for your Corvette, look no further than Pfadt for a unique ride.

Official Release:

New Corvette Coilovers

Following in the footsteps of the recent launch of our premier Double Adjustable coilover the Feather Light Generation DAs, we are announcing the little brother with many of the same features: The Feather Light Generation SAs (Single Adjustable).

The Feather Light Generation SA coilovers are a completely new design for the Pfadt family of Corvette suspension. Most notably, this product separates itself from the competition in the following ways:

INVERTED DESIGN: Placing the majority of the mass on the sprung side of the chassis allows the control arms and outboard components to react quicker and easier without the additional weight of the coilover itself. The result is a suspension system that responds faster to changes in the road whether its highway, local roads, or track surfaces. The less weight that is on that outboard suspension, the better your car will behave – you’ll have a better connection between your Corvette chassis and the ground. Make sure your next set of coilovers are inverted.

LIGHTWEIGHT, HIGH STRENGTH MATERIALS: Gone are the days when coilovers need to be made of corrosive steel components. The Feather Light Generation SAs are an all aircraft aluminum body which boasts high strength and very low weight. With the body and spring perch being manufactured out of anodized high-strength aluminum, you no longer have to worry about corrosion locking the two together. The materials in the new SAs allow pain-free height adjustability with ease with our threaded body. All non-aluminum components (upper mounting stud, lower mount mono-ball) are treated with corrosion-eliminating processes such as chroming, heat treating or using stainless steel. Don’t settle for heavy steel components.

BOA MOUNT, THE NEW STANDARD IN CORVETTE SHOCK UPPER MOUNTING: An idea taken directly from its much more expensive bigger brother, the Feather Light Generation DA; the new BOA mount is a no-compromises solution to Corvette shock upper mounts. Our mount is a zero-maintenance, completely sealed design that allows the FULL articulation required for the Corvette suspension. A common problem in coilover mounting for the Corvette is how to effectively mount the upper shock to the chassis without losing much shock travel and articulation. Common solutions are a clevis design that severely limits shock travel and will effect ride quality, and a “pin top” design that relies on compliance in consumable rubber bushings to deflect and bind the shock, creating an unsealed mount needing eventual replacement. The BOA MOUNT suffers none of these shortcomings as it is a solid mount similar to a control arm ball joint (quiet, durable, maintenance free), that is locked in place and then articulates with the suspension utilizing a low friction internal monoball that is sealed from the exterior elements. On top of all of this, the installation procedure could not be any easier. A simple easy to torque washer and nut retain the whole assembly. If your coilover doesn’t have the BOA mount, be aware of the potential future problems. Take a look at the video to see the new BOA MOUNT in action!

THE CIRC SYSTEM, A REVOLUTION IN REMOTE CANISTERS: A premium feature on the SAs that is unique to Pfadt is the CIRC (Concentric Integrated Remote Canister) System. The idea behind this innovation is to implement a standard racing concept – the remote reservoir – in a lightweight, easy to install package. We integrate the remote reservoir with the shock to maximize suspension stroke for a very smooth ride on the street. The CIRC more than triples the gas volume over a standard coil over. Accomplishing this was no small feat because the remote canister is actual mounted radially AROUND the shock body itself. The result: a large gas volume that keeps the shock operation consistent over a wide temperature range and throughout the stroke. The bottom line: Consistency and performance over the life of the shock. This system permits the entire shaft/piston assembly to operate quickly, efficiently, and last a VERY long time as wear is at a minimum. Get the most advanced racing remote canister on the market for your street suspension. Anything less is a compromise in ride quality. Take a look at the following illustration to see how we package the upper BOA MOUNT and CIRC SYSTEM for maximum shock travel and extreme lowering.

EASY ONE-STEP RIDE HEIGHT ADJUSTMENT: We make ride height adjustments easy to give you the ultimate control in setting your ride height and corner balancing your car. Included in our coilover kit is the single tool that you need to adjust the perch and tighten the set screw to lock the perch in location. Very simple, strong, and reliable. This single perch adjustment is a result of having ALL of the suspension travel required for the Corvette built into the shock body, since features like the BOA MOUNT and CIRC SYSTEM are used to maximize travel and stroke. Any other design is forced to limit the travel range. Our design is the most optimum for the Corvette and will deliver repeatable results time and time again.

FLOATING PISTON INTERNAL DESIGN: The most effective internal design for a performance shock that needs to last a lifetime of street use is the floating piston design, or “non emulsion” design. This design separates the oil volume from the gas volume and allows each to operate consistently despite changes in external conditions. In a standard emulsion shock, the oil and gas are free to mix together and can result in inconsistent performance when operating at low speeds and high speeds respectively. This is not good for the operation of the shock, as inconsistent performance correlates to inconsistent control of your Corvette’s wheels and suspension. Enter the “floating piston” style that isolates the two volumes and moves freely within the shock cylinder. Our floating piston design utilized in the Feather Light Generation SAs will keep your Corvette’s suspension predicable and controllable for a precise feeling on the street and track. GM’s Z06 and Z51 shocks don’t have oil and gas compromises, neither should your coilovers. Be sure to run floating piston shocks on your Corvette. Take a look at the diagram to see how the designs differ.

SIMPLE AND ACCESSIBLE DAMPING ADJUSTMENT: Have you had a hard time adjusting your current dampers because the adjuster is at the top of the shock, hindering your ability to make quick changes from street to track? That will not be a concern for users of the Feather Light Generation SAs because of the inverted design, which places the adjuster on the bottom of the shock in an easy to access location. No special tools are required, and no “adapters” that can frequently break are necessary. All that is required is your hand to grasp the easy-touch rotary knob on the bottom of the shock and dial in your setting with a precise and repeatable feel. The shock adjuster will adjust compression and rebound in one device, so you will not need to be an expert to keep both dialed in at all times. Up front you will feel 40 distinguishable settings with the rear having 24. The adjustment range encompasses soft to stiff valving for customers wanting to fine tune their ride quality or race track set up. The valving in this system will allow you to run very comfortably on the street and then increase the damping for track use if needed, or even higher to accommodate custom spring rates that you spec for your specific Corvette. There will be no guesswork in where to dial in the suspension as we provide a comprehensive tuning guide with the coilovers. When you purchase a Pfadt Feather Light Generation coilover, your purchase doesn’t end at the sale. We are here to continue helping you with our entire package of set-up documents and technical help online and via phone. We help you use your new products effectively to get the results you want. Don’t settle for a company that doesn’t.

DURABILITY: As part of Pfadt Race Engineering’s ongoing effort to support the Corvette community with the best and most advanced chassis and suspension products, the Feather Light Generation series of coilovers (SAs and DAs) are the pinnacle of street performance, track results, and unbelievable reliability. Part of our evaluation for these coilovers has been our in-house, Pfadt-designed, DAMPER DURABILITY RIG. We have run all versions of current coilovers through rigorous testing on this machine for weeks which simulates tens of thousands of miles and literally millions of cycles. Being able to control the testing allows us to test at worst case scenario forces and articulation angles. We’ve also track tested and street tested the SAs to cover the complete set of circumstances. Take a look at the video below and get and idea of what a Pfadt coilover goes through to qualify it as suitable for a Corvette installation. Overall, the idea of moving to a Corvette Coilover suspension is going to give you a huge leg up on other Corvettes in terms of handling and street drive-ability. Removing the transverse leaf spring and OEM shocks will yield a true independent suspension which eliminates any “crosstalk” and harsh ride that the OEM suspension is known for. Not only will this solve any unwanted driving characteristics, but it will also give you the ability to tailor your Corvette’s ride to your specific taste with a large range of ride height and damping adjustments. Whether you want a stiff ride that is nice and low, or a soft ride that is comfortable and at stock ride height, our Feather Lights will accommodate all of the possibilities. If you get a new set of wheels and need to adjust to accommodate the new sizes: no problem. Your new stance is just a quick turn of the spring perch away.

Give us a call today to discuss the specifics of our new Single Adjustable coilovers and how they can transform your Corvette into a predicable, precise handling machine on the street and track. We have relied on over 5 years of Corvette coilover experience to now showcase all of the data we have collected and optimized for this design. Engineered and tested in Utah, made in North America, take advantage of our hard work on your Corvette and reap the benefits.

• Single Adjustment for Rebound and Compression
• Easy Ride height Adjustment at Spring Perch
• Custom Spring Rates Available
• Fully Serviceable
• BOA Mount
• CIRC System
• Inverted, Lightweight Construction
• Easy to acces adjuster on bottom, 40 clicks front, 24 clicks rear
• Durability Tested for Millions of Cycles