LS swaps are one of the hottest things going in the automotive aftermarket, and that includes shoehorning them into Corvettes that rolled out of St. Louis thirty or forty years before the LS1 debuted in 1997. Powerful, lightweight, and relatively drama-free, the ultra-efficient LS engines make big-block power out of a small-block package and get ridiculously high gas mileage. They have no right to be this good…but they are. Fitting one into an early Corvette is easy; there’s plenty of room in Sharks and Midyears to accommodate the compact package, and engine mount adaptors are readily available to bolt it in place. Wiring can be as easy or complicated as you want to make it, and plumbing the fuel system is relatively straightforward. But adding serious LS package power also means beefing up virtually every other system on the car, including the all-important cooling system.
We drove our ’72 coupe to Tray Walden’s Street Shop, Inc. in Athens, Alabama, where we removed the serviceable 300hp smallblock 350 in favor of an LS3 stroker that dynoed at well over 600. Once we had the engine and its new T56 Magnum six-speed transmission in place, we turned to the radiator and the rest of the cooling system. It’s easy to love these cars so much that we forget how old they are, but you’ll quickly remember once you take one apart and find rust. The radiator core support is a classic rust spot due to decades of leaks and overflow. In our case, the support had only surface rust, but still needed to be upgraded to make sure our aluminum DeWitt’s radiator (which was made for LS conversions) would fit.
To hold the DeWitts unit, we ordered a big block radiator core support from Corvette Central. We also required upper mounting brackets (lower ones already come attached to the core support) with rubber cushions, and foam seals to go between radiator and support to make sure all the air flows through the radiator, rather than around it.
Unfortunately, factory hoses wouldn’t fit, so we resorted to bending pieces of metal rod in the basic shape we needed and then adjourned to the local auto parts store, where we wandered through the back room until we found hoses in the general contour and length we needed. Fitting these was relatively simple, as was adding the LS-specific steam line that routes to the radiator.
This wasn’t the end of the work, however. You don’t put 600 hp into a Corvette without intending to use it, and the only legal place to unwind that kind of power is on a racetrack where you are expected to have some sort of “catch can” to keep your radiator from overflowing onto the track. Though we purchased a universal aluminum unit, we couldn’t make it fit into the confines of our engine compartment; we were forced to build our own. Starting with an aluminum bottle, I machined a threaded fitting for the bottom of the can while Tray Walden drew out a lid for it in a CAD program, and then machined it on-site in a CNC mill. Once done, Tray welded up the bottle, adding a mounting bracket. After that we screwed in the hose fitting on the bottom and the breather in the top, and bolted it in place on the inner fender. All that’s left is to send it off to be polished, then bolt it back in place.
Once the upper mounts and the radiator hoses are removed, tilt back and lift it out—and while I’ve done this job alone, it’s much, much easier to do it with two people to safely ease the radiator out.
The core support is a classic rust spot, and ours didn’t disappoint. While this is only surface rust, it only gets worse with time. Also note, the foam seal has deteriorated beyond the point where it’s really doing anything.
The bottom of the core support, showing the lower bracket and cushion that hold the radiator in place. Also note the ground wire bolted to the support—you’ll want to remove that prior to taking the support out, and make sure it’s correctly reinstalled later.
The bottom of the core support, showing the lower bracket and cushion that hold the radiator in place. This is a particularly vulnerable area when the support is shipped—the shipping company bent ours twice—but minor damage can be safely bent back.
The screws on the side of the support can be devilishly hard to get to—the screw head in this case is shown behind the bracket with the two screws in it, and we had to trim some fiberglass to get at the screw on the other side.
Much better: the new radiator core support, sourced from Corvette Central. Available in more than one size, we chose the big block core support to hold the larger DeWitts radiator required to cool the potent LS.
The new core support bolted in place. Be aware, the core support serves as a structural member for the nose of the car, which means the position of the nose may shift once it’s removed. That can complicate aligning all the right holes with the matching holes in the support. We use a tapered rod to lever things into place.
The foam seals, which we also sourced from Corvette Central, in place on the core support. While easy to overlook, the seals are critical to ensure airflow goes through the radiator, rather than around it…which would defeat its purpose.
The extension to the side of the lower bracket is unnecessary for our purposes, so we cut it off. Dress the edge of the cut to remove any jagged edges, finish with some black spray paint to ward off corrosion, and you’re good to go.
Due to the space constraints of putting in the radiator with the engine already in place, we have to remove the fans from the radiator and lay them loosely in place before we can slide the radiator down between them and the core support.
The radiator, core support, and condenser after installation is complete.
The lower radiator hose. Since there is no factory option for an LS installed in a ’72 Stingray, we usd a piece of bent wire approximating the path and length of the hose, then use that to pick the hose that looks closest. Write down the part number, since the bent-wire option may not work if you wind up on the side of the road.
How the steam line is seated on the head: the rear of the mounting block seats against its hole in the head, while a mounting bolt passes through the block and screws down, holding the steam line in place.
Once the hard line is in place, we use a length of hose to connect its outlet to the radiator, routing it across the top of the fan bracket. We hold it in place using a pair of hose mounting clamps screwed directly into the body of the radiator, after making sure there is enough material here to do it safely.
The cooling package complete: radiator, fans, hoses, and both steam and overflow lines installed. Everything required to keep that monster LS cool as well as controlling any little mishaps along the way.
Story and photos courtesy Jeremy D. Clough