Where the C6.R and ZR1 differ significantly are in situations where GT rules actually prohibit the use of the more sophisticated ZR1 components. For example, the ZR1 is equipped with carbon-composite brake rotors, while GT regulations require ferrous (steel) brake discs. And, where the ZR1 utilizes a 6.2-liter supercharged\ V-8, the C6.R uses a naturally aspirated, production-based 5.5-liter small-block V-8.

The Corvette C6.Rs' engines are developed, built and maintained by GM. Designated LS5.5R, the naturally aspirated powerplant is based on the Corvette Z06's 7.0-liter LS7 engine (which in turn was developed with the 7.0-liter race engine used in the C6.R GT1 cars), and is built with a production cast-aluminum cylinder block.

Pending GT2 class regulations specify a maximum displacement of 5.5 liters. The reduction in displacement to meet this requirement was achieved by shortening the crankshaft stroke and reducing the cylinder bore diameter. In accordance with the regulations, the race engines have two 28.8mm diameter intake air restrictors. The LS5.5R engines are equipped with dry-sump oiling systems, CNC-ported aluminum cylinder heads with titanium intake and exhaust valves, and sequential electronic port fuel injection. The race engines use E85R ethanol racing fuel in the ALMS and E10 fuel in Le Mans.