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Old 12-09-2010, 05:43 PM
d^2 d^2 is offline
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454 Chevy Pump Gas Compression

Howdy

I have a new 454 crate motor with cast iron heads with a 8.75:1 compression ratio. I was wondering how high I could go but still run on 89 octane gas?



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Old 12-09-2010, 08:13 PM
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You can go up to about 9:1 on 89 octane. You can even bump it up to 9.5:1 if you carefully tune it with a modest timing curve. However, bumping up the compression from 8.75:1 to 9.5:1 is such a small gain you won`t notice any difference power wise which makes it not worth doing.
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Old 12-10-2010, 07:41 AM
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Depends on cam timing, temperature, and load (gears, trans, weight).

For example. I use a 454, 8.75:1, in a 4200 pound truck, 3.08 gear, th400, and a compcam 260H. It will ping if I pull a light trailer with 89 octane in the summer (95F).

If you are running a mild cam (less than 265 degrees advertised) then stay with the 8.75:1.

In general, A 268 degree cam can handle 9:1, 270 degree use 9.25:1, 280 use 9.5:1, 290 use 10:1.

A BBC will not tolerate compression as well as sbc.
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Old 12-13-2010, 06:32 AM
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I also have a 396 out of a L35 Camaro. It has 10.25:1 in it. Will it ping if I put it in a pickup that I tow heavy loads with?



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Old 12-13-2010, 08:18 AM
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Quote:
Originally Posted by d^2
I also have a 396 out of a L35 Camaro. It has 10.25:1 in it. Will it ping if I put it in a pickup that I tow heavy loads with?
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Most definitely, unless you run 93 or some octane booster.

Vince
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