"There's no magic number as if you put the wrong cam in, it can detonate at 9.5:1. If you have mildly ported heads and a larger cam, it can run fine at 11:1."
+1
Had a guy bring a GTO with a 455 here once that pinged everyplace but at idle!
It was 9.5 to 1 compression, Comp 224/230/110 hydraulic roller camshaft, 1971 HO heads. One of the WORST running 455's I've ever seen, or worked with.
The cam was simply all wrong for it. Basically WAY too good at cylinder filling at lower rpm's, so it acted like it was closer to 11 to 1 compression than 9 to 1......Cliff
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https://cliffshighperformance.com/
73 Ventura, SOLD 455, 3740lbs, 11.30's at 120mph, 1977 Pontiac Q-jet, HO intake, HEI, 10" converter, 3.42 gears, DOT's, 7.20's at 96mph and still WAY under the roll bar rule. Best ET to date 7.18 at 97MPH (1/8th mile),
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