There is often a wide variation in chamber volume on some of the high performance cylinder heads. It is not unusual for the actual compression to be closer to 10.25-10.50 than 11.00-1. I have "several" L78 cars and there is a differnt fuel tolerance for each one. The only way to know for sure is to pull the heads and measure CC's and dome volume and then figure the static compression ratio. It is a lot easier just to set them up to run and back into a fuel mix that works without detonation.
wilma
