After doing some research on the Piston/Head combo's.....Putting 074 heads on a L78 short block would yield approx 9.5 to 1 compression.....doesn't make any sense why the factory would do that in a High Performance application......there was also concerns about the posibility of the closed chamber piston dome hitting the 074 head in the exhaust valve area, even though the chamber was larger ..... Some hit....some didn't......so.....Why would GM put High Performance Aluminum Heads and lower the compression ratio by 1.5 points........Seems more likely that the heads were added at some time in the cars early life by someone who didnt know the difference..
Ken
