1957 Corvette RestoMod Story – Page 4
The LS1 Engine & T56 Transmission
Now let’s get to the business part of this build – the engine! Instead of building the old, tired 283, I decided from the beginning to upgrade to the GenIII block – the LS1.
The LS1 was just as revolutionary as the first V8 small block of the 1950’s. It’s all aluminum, a little over 346 cubic inches (5.7L) and produces 350 stock horsepower. The LS1 was used in Corvettes from 1997 to 2002 with great success. Many hot-rod projects use the LS1 because of its reliability, bottom-end strength, ease of power adders, and light weight. If my budget allows, maybe forced induction?
My choice for transmission was always a manual. Corvettes should not be automatics in my opinion. The Tremec T56 was what I decided. Developed by Borg-Warner and now produced by Tremec, this gear cruncher is used in many high-performance cars like the Viper, Z06 Corvette, Aston-Martin, and Cobra Mustang.
Even if I add forced induction, the strength of the T56 will handle it quite nicely.
The T56 is a double overdrive (5th & 6th gears are less than 1:1) six-speed that can handle up to 450 lb/ft of torque right out of the box.
There are many retailers who sell the T56, and some sell re-manufactured units. Mine was from Keisler and is called the T56 Magnum (Keisler was sold to Silver Sport).
Gear ratios can be custom ordered, by I stuck with the standard 0.50:1 sixth gear. When mated to my rear axle ratio, this meant cruising at 75 mph at about 1,700 rpms.
The Corvette LS1 used a one-of-a-kind oil pan called the “Gullwing”.
You can see above that the pan is flatter with two side wings. This allows for an additional quart of oil, plus the advantage of less oil slosh in high-speed turns – which the C5 ‘Vette did very well.
My new headers fit the C1 frame very well; unfortunately they could not clear the Gullwing oil pan. So a standard LS1 F-Body pan was substituted.
The Gullwing oil pan was developed by GM at their proving ground in Mesa, Arizona. Skid pad testing revealed the oil pump was starved at high rpm driving – which is needed during skid pad testing.
The skid pad is a test to measure G-forces. The top measurement is just before the tires break loose when the car turns a tight circle.
The C5 Corvette with LS1 engine achieved a 1g level – which was better than both Porsche and Mustang of the time.
During the high rpm skid test done by car magazine writers, the oil would be pumped up into the engine so much that no oil was left in the oil pan.
The LS1 internals will not be upgraded for this project. The bottom end of the LS1 is strong enough to upgrade the internals for more performance, but it could make street and highway driving less comfortable – not to mention gas mileage reductions.
I will upgrade induction parts however. The intake manifold will be upgraded to the Z06 style. The cold-air induction system will include direct air from beside the radiator and through a high-flow filter and 4-inch tubing supplied by Spectre Performance. The higher flow of the Z06 manifold, and readily available amount of air will help the performance of the LS1.
For accessories, I went to Street & Performance for billet aluminum pulleys, power steering pump & reservoir, alternator, and radiator overflow. And even though I’m in Arizona, no air conditioning will be initially attached – I know, I’m crazy. But with this little rag top, the A/C probably wouldn’t make any difference anyway. Plus, there’s less parasitic drag on the engine.