L92--LS3 Compression Difference

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Jul 16, 2007 | 02:44 PM

RWC

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Staging Lane

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L92--LS3 Compression Difference

Does anyone know what GM did different to raise compression from 10.5 on the L92 to 10.7 on the LS3? Different head gasket, pistons or chamber volume? Head gasket would be the easiest and cheapest. I've read it has a different head casting #, so maybe that's it.

Jul 16, 2007 | 06:41 PM

Greg Fell

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didn't notch the pistons? seems contrary to logic but...?

Jul 16, 2007 | 08:55 PM

drain89

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I'm wondering also. Hopefully it's a thinner mls head gasket, but I bet it's the pistons.

Jul 17, 2007 | 05:00 AM

ringram

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The valves are different too, perhaps they take up more volume in the chamber!?

Jul 17, 2007 | 11:05 AM

RWC

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Staging Lane

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I hadn't thought about the valves, but the difference is small. I get 1.7 cc's or about .008 thinner gasket. Do the L92 pistons have valve reliefs or are they flat tops? Maybe someone from SDPC can check to see if the LS3 has the same part no. gasket as the L92 and the piston differences. Using a thinner mls gasket would be good.

Jul 17, 2007 | 10:53 PM

drain89

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from the pic I have of the ls3, it doesn't have valve reliefs. the l92 has them. I still would like to know the thickness of the head gaskets.

Jul 17, 2007 | 11:17 PM

RWC

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Staging Lane

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Quote:

Originally Posted by drain89

from the pic I have of the ls3, it doesn't have valve reliefs. the l92 has them. I still would like to know the thickness of the head gaskets.

No valve reliefs (flat tops) would be enough (usually about 2cc) to raise it to 10.7 CR. That would be all they would have to do to get there if everything else is the same. Thanks for the info.

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