1972 Chevrolet Corvette Project Car - Powertrain Swap Preparation

Down The Rabbit Hole - Gutting our '72 project car in preparation for a modern powertrain swap

Jeremy D. Clough Feb 7, 2014 0 Comment(s)
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Those who've kept a keen eye cast across these pages for C3 articles will by now have seen the series we're doing on Scarlett, our chrome-bumper shark project car. So far, we've taken an almost-stock '72 350 coupe and, through a series of a la carte modifications, turned it into something more formidable, starting by bumping the horsepower from 300 to 400 with a Zex nitrous-oxide system.

We've also dramatically improved the car's handling with Addco sway bars and wider 275-series tires on 17-inch Summit Racing wheels, as well as suspension mods including a Muskegon front rebuild and a Van Steel rear coilover conversion. Additionally, we're now hauling it to a quick stop with Wilwood brakes—six pistons up front, four in the back—and protecting ourselves with Dragvette halfshaft loops and a fire extinguisher.

The road is more visible thanks to ECPB electrical headlight and wiper-door actuators that actually work, supplemented with Cibié driving lights. Finally, a pair of Corbeau seats keep us both comfortable and well planted.

The problem is, in the words of Jeremy Clarkson, we need more, bigger stuff. More faster. So far we've stayed fairly close to factory systems such as the motor, trans, and chassis, with significant gains at reasonable cost. Call it Phase 1. Welcome to Phase 2, whereupon we follow the white rabbit down the performance hole, and all that "reasonable" stuff drifts away like smoke on the wind.

The ultimate goals for this car are threefold: 11s in the quarter-mile, 1g on the skidpad, and 20-plus miles to the gallon, closely tracking the Pro-Touring ideals. Doable in a 40-year-old car, but not easy. One of the first steps is to repower the car with an LS-series engine—namely, the 635hp LS3 stroker we described in our "Building the Beast" series. While we'll tackle the handling side of the equation later, getting the LS (especially one that stout) into a C3 requires modifications to the stock frame, as well as changing other systems such as the transmission, cooling, fuel delivery, wiring, and gauges.

1972 Chevrolet 2/28

Both the initial teardown and rebuild are being done at Street Shop, Inc., in Athens, Alabama, where owner and personal friend Tray Walden has lent his considerable expertise to the build. While Walden is best known for his custom frames that marry late-model Corvette suspensions to old-school Vettes (for which he holds two patents), he's also well versed in the engine transplants and other modifications required to fully modernize a vintage Corvette. Fortunate thing, that. We'll start with the teardown in this article, with follow-up articles on each of the major systems as we get to them.

After unbolting the hood, the first part of disassembly was to drain as many of the car's fluids as possible, starting with the gas tank. Not only is it safer to reduce the amount of fuel you're dealing with, it also makes the tank lighter, which is much appreciated for anyone who's ever balanced one on their head. Fortunately, Scarlett has an electric fuel pump, so we disconnected the rubber fuel line where it enters the carb, grafted on a longer length of hose, routed it over the fender into a bucket, then simply turned on the pump until the tank was nearly dry.

Transmission fluid and oil were even easier: Once we had the car up on the lift, it was just a matter of unscrewing the drain plugs. Getting the coolant out of the engine, however, required cutting the lower radiator hose, which meant a couple of us got soaked with antifreeze. Note to self: Wear old clothes.

It's possible to do all this work by yourself, but the team approach eases the process considerably. With the fluids out, I dropped the spare tire and its well from the rear of the car, then went to work on removing the gas tank, which is to be replaced with a larger stainless Rock Valley tank with an in-tank Aeromotive pump. Meanwhile, the others—Walden, Ted Whitney (also of Street Shop, Inc.), and the long-suffering Phillip Price—started in on the transmission and engine.

1972 Chevrolet Corvette Drain Gas 3/28

01 One of the first orders of business was to drain the fluids, starting with the gas tank. Since Scarlett has an electric fuel pump, we disconnected the rubber fuel line from the carb, grafted on a longer length of hose, routed it into a bucket, and turned on the pump.

1972 Chevrolet Corvette Spare Tire 4/28

02 The spare-tire carrier came out first, followed by the fuel tank. It’ll be replaced with a larger, stainless tank from Rock Valley, and the factory line will be upgraded to ethanol-compatible braided hose and fittings from Earl’s.

1972 Chevrolet Corvette Remove Driveshaft Safety 5/28

03 Before the transmission could come out, we had to remove the driveshaft safety loop, shown here, as well as the driveshaft itself.

1972 Chevrolet Corvette Remove Exhaust 6/28

04 Since the exhaust pipes pass through the trans crossmember, they had to come out for it to be removed. And since they were welded to the headers, there was only one way to make that happen.

1972 Chevrolet Corvette Crossmember 7/28

05 Three bolts on either side of the crossmember hold it to the frame: Two bolt up directly, while one goes fore-and-aft through a bracket-type arrangement. At this point, the transmission is being helped up by a jack.

1972 Chevrolet Corvette Atf Line 8/28

06 While one of the ATF lines could be unbolted, the other wouldn’t come loose. The sight of leaking fluid is one you should get accustomed to.

1972 Chevrolet Corvette Unbolt 9/28

07 Unbolting the transmission from the rear of the motor required a long assembly of extensions, as well as a fair amount of patience.

1972 Chevrolet Corvette Remove 10/28

08 With all the cables, lines, and bolts removed, the Turbo-400 came back and out. It’ll be replaced by a T56 Magnum six-speed from American Powertrain.

1972 Chevrolet Corvette Unbolt Motor 11/28

09 Before dropping the car to pull the engine, we used a wooden block and a ratchet strap to support its weight, then unbolted the motor mounts.

1972 Chevrolet Corvette Remove 12/28

10 While the motor mounts had already been loosened, the headers were among the other parts that had to be removed in order to free the engine.

1972 Chevrolet Corvette Accessory Drive 13/28

11 The accessory-drive items also needed to be removed for motor clearance to come out, as well as the air cleaner and carburetor.

1972 Chevrolet Corvette Remove 14/28

12 With a lift plate on the intake chained to the electric winch on the crane above, the old motor yielded its position under Scarlett’s hood. This is a job that benefits from more than one set of hands.

1972 Chevrolet Corvette Remove 15/28

13 The radiator came out next. It will be replaced, along with a fresh core support from Corvette Central. Pulling the radiator is another two-man job, especially if you value your paint.

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