The present compression ratio of the Clipper and Packard engines is a conservative 8-1/2 to 1, while the Hudson and Nash engines have an even more conservative 7.8 to 1. If one chose to use the heads of the 320-cubic inch Packard engine on the 352-cubic inch engine, a compression ratio of 9-1/4 to 1 would be obtained. To obtain a compression ratio of 7.8 to 1 on the Hudson and Nash, the heads from the 352-cubic inch engine are used.