Quote:
Originally Posted by GoreMaker
Well, a stock W72 400 (6X-4 heads, 8.2:1 static compression ratio, very pump gas friendly, 38 to 40 degrees total advance stock) has a dynamic compression ratio of 6.42:1. That means that at low RPM, your engine actually compresses the mixture less than a stock W72 does. But depending on your LSA, your volumetric efficiency might increase a lot more as RPMs go up, so cylinder filing is probably higher in that range. Honestly though, if you're running aluminum heads, you're probably fine with 87 octane. If cast iron, you'd likely want 91 or 93 just to ensure you don't ping at WOT. That's a pretty low dynamic compression ratio.
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Thx, ya Ported #64 HO heads I've always ran 91 in the past. Just wanting to be sure. I kept my timing back to 30-31 because with the headers and flowmasters, I could never hear pinging clearly. But in spring and fall I ran mid grade a few times and she seemed OK. I never pushed her on it tho so.
It's a Melling SPC-8 cam. advanced 4 deg if it helps