compression ratio??

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Sep 19, 2007 | 07:31 PM

draycer

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compression ratio??

If I use SE high comp cast piston set 10.25:1 will I actually get 10:25:1? I'm trying to be at 9.8:1 and hear I probably can't get there with flat tops and a .030 gasket. Anyone actually test this on stock size comb chambers?

Thanks

Sep 19, 2007 | 07:35 PM

ReeseSS

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From: Cape Coral, FL

RE: compression ratio??

Domed pistons will not keep you under 10 to 1. Manufactures specs are pretty dead on. Youwill have to mill the heads with flat tops to get 9.8 to 1.

Sep 20, 2007 | 08:20 AM

mentor70

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From: Diamond Bar, California

RE: compression ratio??

C/P pistons and SE has a forged pistons with a 4cc dome. out of the box with a 84 cc head i belive, is a 9.5 to 1, Im not 100% on this, but i think if you head is milled to 80 to 82 ccsit will be 10. to 1

Sep 20, 2007 | 03:27 PM

draycer

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RE: compression ratio??

Yes I've been looking at these pistons. SE rates them 9.6:1. If I use these with a .30 gasket you think I will be close?

Sep 20, 2007 | 04:27 PM

mentor70

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From: Diamond Bar, California

RE: compression ratio??

Yes, but it would be best to have the cylinder heads CCed and equalized so you know for sure waht you have.

Sep 20, 2007 | 04:44 PM

Kingofcubes

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Joined: May 2007

Posts: 851

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From: Mitchellville, Ia.

RE: compression ratio??

On a 98" the formula is 3.937x3.937x.7854x16.387x4=798cc's[/align]Gasket is 3.937x3.937x.7854x.030"x16.387=6cc's[/align]If head is 86cc's 86+6=92+798=890/92=9.7 to 1= flat top piston not taking into consideration the valve pockets (1cc approx.)[/align]This is about as close as you can get w/o actually oiling it out.[/align]So 10.2 to 1 would be about right with a 3cc dome.[/align]So for every .040" you take off the heads you go up .6 compression[/align]Hope this helps[/align]

Sep 20, 2007 | 05:11 PM

draycer

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RE: compression ratio??

Thanks this helps alot!!

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Sep 20, 2007 | 09:17 PM

mentor70

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From: Diamond Bar, California

RE: compression ratio??

Quote:

ORIGINAL: Kingofcubes

On a 95" the formula is 3.937x3.937x.7854x16.387x4=798cc's[/align]Gasket is 3.937x3.937x.7854x.030"x16.387=6cc's[/align]If head is 86cc's 86+6=92+798=890/92=9.7 to 1= flat top piston not taking into consideration the valve pockets (1cc approx.)[/align]This is about as close as you can get w/o actually oiling it out.[/align]So 10.2 to 1 would be about right with a 3cc dome.[/align]So for every .040" you take off the heads you go up .6 compression[/align]Hope this helps[/align]

Good info, thanks KING!