Originally Posted by Lee Stewart
What was the highest compression used in a factory built high performance engine? (one that was installed in a vehicle)
The 1962 Dodge Max Wedge 413 (420HP) and the 1963 Max Wedge 426 (425 HP). Both used a compression ratio of 13.5 to 1.
The ZL1 and L88 427s used 12.5 to 1