Re: 9.2:1 CR in 327?

Posted by Owen_Dyneto On 2012/6/23 10:15:12

Based on another 327 I'm familiar with that had the head milled excessively (we had to grind the combustion chamber to provide valve clearance) and had compression probably in the same range you anticipate, I'd say that if you have enough valve clearance and can get high-enough octane gasoline to control the preignition without having to retard the timing, you'll probably be OK but I doubt very much that you'll experience any improvement in engine performance (power). Packard found about 8.7 to be the maximum for flat head in-line 8s (as in the 359); GM found much lower CRs to be the maximum, for example in the last Pontiac in-line 8s.