Compression Ratio Math Check Please!

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Mar 26, 2012 | 07:44 PM

LS1 Racing

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From: 78°14′46″N 15°27′56″E

Compression Ratio Math Check Please!

Just want to confirm my compression ratio for my LQ4 build:

Stock bore/stroke/piston LQ4
243 heads milled .017
Stock .051 thickness head gasket

I'm getting 11.1:1

Can anyone confirm my math?

Thanks in advance!

Mar 26, 2012 | 07:51 PM

batboy

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Valve relief on the pistons (like 4cc)? Do you know how far out of the hole the pistons are (deck clearance)? What size compression chambers on the heads? Is that about 60cc?

Mar 26, 2012 | 08:02 PM

LS1 Racing

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From: 78°14′46″N 15°27′56″E

I believe the stock reliefs on an LQ4 are -2. Chambers are 61cc. This is an untouched bottom-end, so deck clearance is stock.

Mar 26, 2012 | 09:34 PM

batboy

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Using a typical deck clearance of 0.006" out of the hole, I get about 11:1.

Mar 26, 2012 | 09:41 PM

LS1 Racing

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From: 78°14′46″N 15°27′56″E

Quote:

Originally Posted by batboy

Using a typical deck clearance of 0.006" out of the hole, I get about 11:1.

Thank you!

Mar 26, 2012 | 10:18 PM

bww3588

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There is a lot more than 2 cc's worth of dish on an Lq4 piston. I just have valve reliefs in my flat tops and they are 3.2 cc's. I'd say it's 6 cc's or more.

Mar 27, 2012 | 08:33 AM

5.3LJimmy

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From: Napoleonville, LA

Stock LQ4 piston has a 7cc dish. Using that along with your info and -.006" deck height I get 10.6:1 CR.

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Mar 27, 2012 | 11:16 AM

PREDATOR-Z

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From: BFE

I get around 10.6 SCR

Mar 27, 2012 | 12:15 PM

#10

lemkerailroad

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From: dayton ohio

dont mean to hijack but i have the same question

heres my specs:
pistons -6cc
799 heads milled .019
cc head @ 62cc
piston to deck -.013
.075 between piston and flat of head
3.905 bore
.050 thick gasket

any help would be great

thanks in advance

Mar 27, 2012 | 01:00 PM

#11

Pumba

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From: Northville, Michigan

Here is a good web site to bookmark that will calculate your compression ratio:

http://www.kb-silvolite.com/calc.php?action=comp

-

Mar 27, 2012 | 01:31 PM

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dodson55

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From: monticello, ky

my pistons had a 6 cc dish and my heads were milled .015 and the chambers measured 62 cc i didnt measure my piston out of hole but i guessed them at .005 out of the hole i figured my compression to be just a little over 10.5 i am going to say you have around 10.6

Mar 27, 2012 | 01:42 PM

#13

lemkerailroad

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thanks for the web site

saved it in fav's

Mar 27, 2012 | 01:54 PM

#14

LS1 Racing

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From: 78°14′46″N 15°27′56″E

Quote:

Originally Posted by Pumba

Here is a good web site to bookmark that will calculate your compression ratio:

http://www.kb-silvolite.com/calc.php?action=comp

-

Thank you! I'll bookmark that for the next build!

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Compression Ratio Math Check Please!

Compression Ratio Math Check Please!

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