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.

While it's possible to pull the trans and motor as a single unit, we decided to drop the Turbo-400 automatic from the bottom and then remove the engine from the top. Among other things, this means less weight to deal with. To disconnect the transmission, we removed the driveshaft and its safety loop (which mounts to the transmission crossmember), as well as the exhaust pipes, which met the Sawzall. After supporting the trans with a jack, we unbolted the crossmember from both it and the frame and laid it aside.

When you get this "personal" with a car, you're going to find things that surprise you, and in this case we were surprised to find that the crossmember had been seriously caved in by an unidentified item I'd previously hit on I-985. (The 7/16-inch wrench we found in the fresh-air vent and the cigarette butts left over from someone using the recess below the shifter assembly as an ashtray are also worth noting.) I never knew what it was—perhaps an anvil from the indentation it left—but seeing the damage, I'm grateful it struck the crossmember and not the fiberglass floorpan.

After removing the fluid lines, speedometer cable, and shifter linkage from the trans, we unbolted it from the rear of the motor and slid it backwards and out. Next, with the car still raised, we used a wooden block and a ratchet strap to support the weight of the engine, then unbolted the motor mounts. With the fuel line already disconnected, we removed the headers, ground straps, and other wiring as well as the throttle cable, heater hoses, and upper radiator hose. Taking off the Holley carb let us bolt a lift plate to the intake, and after rolling the car beneath the crane, we hooked the chain to it and carefully guided the 350 up and out of the car. While many people lift the motor out with a cherry picker—and there's absolutely nothing wrong with that—the pushbutton ease of the electric motor on the crane was greatly appreciated.

With the two big parts out, myriad small things remained under the hood: unbolting the radiator and core support, stripping out the old wiring harness (as well as what little remained of the vacuum system), and pulling the original air-conditioning system, which had long ago ceased to cool anything but my enthusiasm for summer road trips. Once all that was done, we plugged the holes in the firewall, and Scarlett went back out under the sun for a good pressure washing, followed by some Scotch-Brite-and-black-paint work to neaten up the engine compartment a little.

The interior came next. After unbolting the Corbeau seats, we lifted them out and undid the interior screws to remove the dash components (which we'll cover in more detail later), as well as the steering column, brake and gas pedals, and shifter and emergency-brake consoles. Wiring and vacuum hoses were both cast away with the same reckless, gleeful abandon, and the firewall insulation—which looked a lot like home for Rizzo the Rat—went with it. With the interior stripped to the firewall, we found a little surface rust on part of the birdcage. We hit it with some neutralizer, then repainted it in a nominally correct pale green.

As I write this, about two months have passed since I pulled Scarlett into Street Shop under her own power. Reassembly is well underway, but you can still see clean through the car from many angles, and I can't help but feel a little like Wile E. Coyote after he strapped himself to a rocket and lit the fuse. With parts for the car scattered across about four states, we're well and truly down the rabbit hole, and it's been quite some time since I've seen an actual bunny.

I have, however, seen a pretty stout LS3 parked between Scarlett's frame rails. And next month, so will you.

1972 Chevrolet Corvette Wiring 16/28

14 With the powertrain removed, it’s time to get to work on the little stuff—things like the wiring harness, the remnants of the vacuum system, and the factory A/C—as well as doing a little cleanup.

1972 Chevrolet Corvette Twist 17/28

15 This photo sums up why we’re replacing the harness with a new one from Zip: Yes, that’s a twist nut. IT pro Phillip Price was particularly horrified by this, as well as the duct-tape “insulation” on a couple of the wires.

1972 Chevrolet Corvette Car 18/28

16 Scarlett takes a trip outdoors for a little scrubbing and pressure washing. While we hadn’t removed all of the A/C components from the firewall at this point, we did make sure to plug all the holes in it to keep water out from under the dash.

1972 Chevrolet Corvette Before 19/28

17a Before and after: Following the basic cleaning, it was time for a little Scotch-Brite-and-paint action in the engine compartment. After all, you won’t have this chance again for a while.

1972 Chevrolet Corvette After 20/28

17b Before and after: Following the basic cleaning, it was time for a little Scotch-Brite-and-paint action in the engine compartment. After all, you won’t have this chance again for a while.

1972 Chevrolet Corvette A C 21/28

18 The A/C box was next; removing it requires work to be done on both the interior and under the hood (shown). The factory system will be replaced with an aftermarket setup from Vintage Air.

1972 Chevrolet Corvette Firewall 22/28

19 With the lower dash pads and A/C components removed, the disintegrating firewall insulation looked like an excellent nesting spot for rodents.

1972 Chevrolet Corvette Dash 23/28

20 The wiring under the dash looked better than the wiring under the hood, but that’s not saying much. It’s all going away, as is the handle for the hood latch, which will be rendered unnecessary by the addition of a pinned hood.

1972 Chevrolet Corvette Shift 24/28

21 With the dash and gauge cluster removed, the shift console came off next. Since Scarlett began life as an auto, we’ll be replacing the console with a manual-trans version provided by Paragon.

1972 Chevrolet Corvette Remove Shifter 25/28

22 Removing the shifter assembly and the seal beneath it creates a hole through the bottom of the interior. Since we’ll be putting a T56 six-speed in the car, I expect even this relatively large opening to require additional clearancing.

1972 Chevrolet Corvette Steering 26/28

23 We may never know why GM built some of the C3’s steering-column-assembly parts out of unpainted cast iron. Whatever the reason, these are coming out for a little bead blasting and paint. The column itself also came out, greatly easing the process of removing and reinstalling the pedal assembly.

1972 Chevrolet Corvette Surface 27/28

24 After finding a little surface rust on part of the “birdcage,” we hit it with some neutralizer and repainted it in a nominally correct pale green. We’ll be replacing the factory dash pads with replacements from Corvette America, and the gauge console with one from Volunteer Vette Products.

1972 Chevrolet Corvette 28/28

25 A sign of some of the goodness yet to come. After the slightly dismaying sight of most of Scarlett’s insides being on the outside, we’re looking forward to the more exciting process of rebuilding.

Sources

Street Shop, Inc.
Athens, AL 35611
256-233-5809
www.streetshopinc.com
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