I've read - as my post said waaaayyyyy too much research - that these heads have small valves - 1.78 /1.50 which is the same as the original heads valve sizes - but have an aggressively small "Fast Burn" chamber that runs around 10cc smaller than the original stock heads - which is my "cheat" to get a higher compression ration without pulling the motor itself with the bonus of hardened exhaust valve seats so no worries about gas....but I could be totally wrong which is my concern.
