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Old 05-25-2005, 04:38 PM
454C10 454C10 is offline
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Man! That depends on a bunch of things! But in the case of an old V8, the cam profile is the biggest player.

You should be calculating the dynamic compression, which also uses the cam specs.

I have a 11:0 sbc with a 292H comp cam in a light car and a 5spd with a 3.90 gear and have not problems with 93 octane and 38 degrees of timing.

My 70 1/2 c10 truck with a 454 (8.75:1), with a mild rv cam, 3.08 gear, and automatic will detonate if I run my timing up too high (over 38).

In general, a sbc and handle more compression ratio than a bbc. And, a lot of little import engines can burn 87 octane fuel with 10:0 cr. So you should be more motor specific.

So in a sbc with a mild cam (under 210 degrees duration at 0.050) 9:0 should be about max.
a cam between 211 to 219, 9.5:1 cr
a cam between 220 and 230, 10:1 cr
a cam between 230 and 240, 10.5:1 cr
a cam between 241 and 250 11:1 cr

This also depends on car weight and gear. More weight and less gear (more load) would need less compression.
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