1966 Corsa Rear Engine Conversion
This 1966 Corsa
The car was bought in 1979 for the sum of $50. The original build of the car used a 215 cu. in. Oldsmobile V8 mounted in the rear running in reverse rotation and mated to the factory 4-spd. transaxle. The transmission had been modified with four spider gears and a HD input shaft. After an engine rebuild which found the little 3.5L V8 stroked to 4.2L the reverse camshaft finally let go. The car sat in the garage for 2 years before it was decided that we would replace the V8 with something more modern. The Corvairs reverse rotation in comparison to the vast majority of the automotive industry posed a problem in sourcing a power-plant. The decision was made to sell the Oldsmobile V8 and fit the car with something a little more powerful with a transmission to match. Not wanting to put a heavy iron block V8 in the
rear of the car we decided that aluminum was the way to go. The
transaxle was a no brainer, the only transmission that could stand up to
the abuse of 385 Hp was from Porsche. We called up world renowned Hunter
Motorsports and had them build a 930 Turbo transmission.
The engine came from a 2003 Corvette with low
miles.
Since the throttle originally ran with a drive by wire system, the throttle body was swapped out in-favor of a Camaro unit which uses a traditional cable. Due to space constraints the intake manifold needed to be turned around. This is a simple operation as the engine was designed to have it face either way. The Throttle body now sits right under the fresh air vent at the back of the window. No interior cutting or modification was needed. To an onlooker the car looks stock. Now that the engine was dressed it was time to mock up mounts. The engine uses off the shelf LS1 hotrod mounts that use a standard GM truck rubber bushings, this ensures the engine runs smooth. One benefit of using the Corvette engine was the low profile oil pan. I wouldn’t recommend completing the swap without it. The front transmission mount is a mating of the original Porsche and Corvair units. Not wanting excessive vibration it retains rubber mounts. The engine itself is held in place by the 2 mounts and a cradle made from 1x2 steel square tubing. This is very similar to what was on the 215. It provides ample support without adding a lot of weight. The rear cross section of the Corvair had to be notched 1” to clear the LS1’s large bowl like main pulley. This was done by cutting in with a plasma cutter and re-welding in the metal. At a glance the operation looks factory. The real hurdle in the installation was the suspension. A Porsche uses suspension pickup points from the body, while the Corvair uses lower arms from the transmission. Brackets were made to link the lower arms and additional upper arms and bolted to the Porsche transmission. The axles themselves are off the shelf Empi Drag pack units capable of supporting 600Hp. Unlike a Corvair they are floating. We used new Porsche CV’s for both the inner and outer units and had a local machine shop fabricate some adapters. The outer Porsche axle bolt pattern is identical to that of a VW with the exception of the patterns diameter. Plates were made in 3/8" steel and the axles were bolted in. Some trimming had to be done to the rear suspension arm to clear the massive CV’s. The Porsche factory shifter is nearly identical to that of a stock Corvair. A few inches was added to the Porsche tubular linkage and bolted in. On lookers would be hard-pressed to tell the difference between the 2 units. The clutch cable operated much the same way. It was just a matter of getting an extended cable. We opted for a Stage 2 clutch and pressure plate from Kennedy so a heavier cable was required. The LS1 is quite popular in the hot-rodding world and a off the shelf harness from Howell engineering was purchased. These harnesses come complete with factory GM weather pack connectors and well labeled. Wiring took no more then a few hours and only consisted of hooking up the engine connectors and wiring a few grounds and positive terminals. After that just turn the key. Cooling the V8 is much like any other V8 vair installation. The radiator is a Griffin 4 core aluminum unit with the fan from a C6 Z06 Corvette. Having a son that works for GM comes in handy. The tubes under the car are aluminum conduit used for electrical purposes. It not only serves as a better heat sink but won’t cause any adverse reactions with the aluminum block. In an effort to keep the car looking stock the only front end modification is a slight cut out under the car. The advantage to a modern aluminum V8 is that the motor will run at 190 all day long regardless of the condition, and even the factory settings don’t turn on the cooling fan until the vehicle hits 215 Degrees. The system does use a steam bleed in the heads which requires an overflow tank in the rear, this was sourced from a 2004 Corvette. Adding nearly 400hp to a vehicle requires other
changes to be done. Brakes were another area of concern. Thankfully Dave Clemens of Corvair autocross fame provided a very comprehensive, well engineered kit. We also opted to have stainless flex lines. The addition of a master cylinder and vacuum operated booster round out the upgrades to the braking with a custom setup added in the rear. The car rides on Koni shocks with Crown sway bars. We get quite a few questions about the wheels, they are from vintage wheel works www.vintagewheelworks.com the model number is VF48 and they are very reasonably priced. They measure 16X8. Okay, How heavy is it? This is the question when answered raises the most eyebrows! With a rear engine installation weight becomes much more of a factor then it does with a mid engine. Using an iron block in a mid engine V8 car isn’t a bad thing as it’s distributed so well. A rear engine car with 600 Lb of iron V8 would be disastrous. The engine fully dressed from the factory with
the AC compressor, PS pump , wiring harness and heavy cast iron exhaust
manifolds comes in at 447 Lb. with the removal of the PS pump , AC and
cast manifolds our engine came in at 402.7 Lb weighed on a UPS freight
scale.
A Stock Corvair engine and transmission weigh in at 456 Lb. (Frank Parker supplied) A Corvair Transmission Weighs 149 Lb. (Frank Parker supplied) The Porsche 930 Transmission weighs in at 113 Lb. The additional weight to the rear of the vehicle is 60 Lb. Consideration also has to be made for the coolant pipes and radiator + fluid. The only effort that has been made to reduce weight was the removal of the back seat and the addition of lighter Recaro bucket seats. The final result is a car with 3 times the HP it originally had with the addition of less then 100 Lb. The car has made many trips from Ontario to
shows in the US without incident. This build was a labor of love between the “ Doc” as he is called and his 3 sons Christopher , Jonathan and Cameron. And we can’t forget about mom who put up with all of it! J. McCreery For specific comments or questions contact Jonathan at Jonathan.McCreery@gmacfs.com
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