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how do you figure compression

885 Views 2 Replies 2 Participants Last post by  Murdoch
hey all, i'm just curious, i've heard it can be done i'm just wondering if anyone has a formula or something, like take my engine for instance. it's a 440 with .30 overbore flat top pistons, stock thickness head gaskets, no milling done to either the heads or block and 906 heads. what's my compression and how do you get it?
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There is an online calculator to find compression ratios here:

Give that a try. Standard bore 4.320 and the standard stroke is 3.750. Deck height is 10.725. You are going to have to figure out what the gasket thickness is and what the head volume is (in CC's) and what the pistons are.

Hope this helps.
thanks white, the only problem is my truck or engine isn't here with me so i can't measure anything. i'm hoping someone with expeiance in this sort of thing will know what 906 heads have and what the pistons and what not are.
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