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what will the compression ratio be for an LS2 with LS3 heads?

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what will the compression ratio be for an LS2 with LS3 heads?

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Old

Nov 19, 2019 | 08:52 AM

#1

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Staging Lane

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what will the compression ratio be for an LS2 with LS3 heads?

Have a freshly rebuilt LS2 and will be bolting on CNC ported GM performance LS3 heads. the Ls3 heads have 68.5cc combustion chambers compared to the LS2/243 heads that have 64.5cc combustion chambers. Anybody know how much 4cc's will effect compression the ratio???

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Nov 19, 2019 | 09:31 AM

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Staging Lane

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Probably lose about half a point of compression.

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Nov 19, 2019 | 10:30 AM

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I came up with 10.4:1 LS3 head with 68.5cc .051 gasket on an LS2. Now with a .040 gasket it comes up to 10.7:1...

Milled LS3 heads to 64cc with a .051 gasket 11.0:1 and with 64cc and a .040 gasket 11.3:1... compression may vary slightly.

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Nov 19, 2019 | 10:38 AM

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Staging Lane

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thanks. I can live with 10.5.

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Nov 20, 2019 | 08:08 PM

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Quote:

Originally Posted by Brer Rabbit

thanks. I can live with 10.5.

Go with the .040" head gasket...….

KW

Old

Nov 20, 2019 | 09:28 PM

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I'm getting 10.72:1 CR if the factory pistons are 0.010" out the hole.
Same calculation using a 0.040" gasket = 11.02:1 CR

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Nov 30, 2019 | 10:08 PM

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I have built ls2 and im wandering same I have 58cc heads and 12.0 comp if I do 68cc how much will it lower comp

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Old

Dec 1, 2019 | 12:13 AM

#8

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Quote:

Originally Posted by caviness

I have built ls2 and im wandering same I have 58cc heads and 12.0 comp if I do 68cc how much will it lower comp

It will get you down to a hair under 11:1

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