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Compression Ratio Question (LQ4 + L92?)

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Old Oct 12, 2009 | 01:23 PM
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Default Compression Ratio Question (LQ4 + L92?)

What sort of compression ratio can I expect on a factory LQ4 with L92 heads?

It's a very general question with alot of factors, but I'm seeing if it's taking me in the wrong direction. I want to keep the low compression for boost.

Robert
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Old Oct 12, 2009 | 02:21 PM
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I did a search and came up with 70cc chambers in the heads, vs. 72cc for 317 heads commonly found on 6.0L engines. So a very general answer is, yes, you may be going the wrong direction, but not by much. I plugged some numbers into the DCR calculator I use and came up with 9.46:1 for 317's and 9.66:1 for L92's.

If you are going to be adding much boost, it makes sense to step up to a forged piston anyway, at which point you have several options to get your compression exactly where you want.
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Old Oct 12, 2009 | 10:45 PM
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So, it looks like some forged pistons are in my future... Any ways to get around that? Building it around twins at 3-5 psi.
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Old Oct 12, 2009 | 11:58 PM
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I got 9:4:1 with 0.054 MLS cometic gaskets with the 4.190 head gasket bore diameter. Thats with 70cc.
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Old Oct 13, 2009 | 08:52 AM
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Factory internals? Any more info on your setup?
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Old Oct 13, 2009 | 02:02 PM
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Thats not my setup. I looked it up. With all factory specs.
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