Old vs. New: Engine

For me this is a no brainer. You certainly can save significant money going with a donor engine (e.g. LS1, LS6). The GTM achieved the its extreme performance numbers with a LS7 hooked to a Porsche G50 transmission, and 0 - 60 in 3.0 seconds flat is something everyone should sit up and take notice. If we take the nominal GTM curb weight of 2400, then the power-to-weight ratio for the demo car 0.210416 HP/lbs.

The curb weight for Corvette Z06 is 3180 pounds. The LS7 is the base engine for the Z06 and this has a p-t-w ratio of 0.158805 HP/lbs.

My 2003 C5 (as currently configured) has a curb weight 3214 pounds. It has a modified LS1 engine and it has a p-t-w ration of 0.124455 HP/lbs.

The base LS3 engine produces 430 HP. In a GTM, the p-t-w ratio is 0.17916 HP/lbs. This is already higher than the Z06, which has a published top end speed of 198 mph.

For emission conscious locales. GM provides green E-Rod engine with the same p-t-w ratio. I only include this engine for completeness. It is not on the list for engines in my GTM.

For close to the same money as the base LS3, there is a more powerful version called the LS376 engine that produces 480 HP. In a GTM, the p-t-w ratio is 0.2 HP/lbs. This engine set up approaches the powerful LS7 used for the demo car. Now we're talking! The MSRP is $8,075. If you shop around, this engine can be found for as little as $6,100.

Granted horsepower isn't everything, but it is the heart of the beast.

The Donor Car - Part 2

The donor car is a cost effective method for acquiring the parts needed for the build. The donor is a cadaver that will never roar down a twisting country road again. So you have to ask yourself what happened. The car either was the victim of a flood, theft or crash. (Stay away from the fire damaged ones. The reasons become obvious, once you look.) The insurance company deemed it unrepairable, and that means there was in excess of $20,000 damage to the vehicle. This number is based on the current replacement cost for a low end Corvette C5.

The major subsystems provided by the donor are as follows:

• Front suspension
• Engine
• Rear suspension
• Rear CV joints
• Emergency Brake Assembly
• Fuel Delivery
• Cooling system
• A/C 
• Brakes
• Miscellaneous (basically everything else)

Factory Five says the donor needs to be a C5. This is the path of least resistance, but many of these subsystems are common across generations for years 2003 to 2009. There is a substantial financial argument to be made for donor with a working engine.

My perfect donor is as follows:

• 2008/2009
• Larger wheels (18 front / 19 rear) - I'd scavenge these for the Big Yellow Toy.
• Big brake upgrade
• LS3/LS7 engine
• Intact suspension
• Intact instrumentation

This poor thing has too much damage for the GTM project. My first clue was lack of wheels and anything to hold them along the driver's side. The love of my life has already indicated that I need to make sure the wheels stay on the car.

This car on the other hand got hit on the passenger side. There is a substantial mess inside, but the mechanicals look good.

As I said, there is a substantial cost savings going the donor car route. The opportunity to acquire a working LS3 or LS7 engine plus the majority of the parts needed for assembly needs to be considered. Copart and Ebay are the easiest places to look for salvage or unrepairable titled cars.