Quote:
Originally Posted by zippy
So my static is 10.6, Dynamic via calculator is 6.3. What is that telling me?
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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.