comp. ratio, l92 heads
Thread Starter
Staging Lane
Joined: Jan 2011
Posts: 59
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comp. ratio, l92 heads l92 heads on an l94 motor with the stock dish pistons. the heads have 68cc chambers. im curious to know about what the compression will be. my math says around 9.5 to 9.7:1 compression. id like some other opinions, can anyone help me out?
Here's some info that I found on another site...
Stock: 70cc
-.010: 69cc
-.020: 67.5cc
-.030: 66cc
What does this mean? It means on an LS2, you need to mill the heads .030", and run a .055" gasket to keep 10.9:1 compression. the stock LS2 heads are 65cc, and the stock gasket is .060" (im pretty sure on that gasket, but someone correct me if im off). With a stock .060 gasket and 66cc milled L92's compression is 10.77:1.
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Konnie the Goat
01-21-2010, 10:44 AM
stock LS2, unmilled l92's (72cc), .055 gasket= 10.17:1
with a .030 gasket, 10.78:1
You also then have a Piston to head clearance of just .020", as most pistons are .010" out of the hole from the factory. Thats an awful tight squish area, and will hurt power and emissions.
In short, mill the heads.
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Stranger808
01-21-2010, 10:47 AM
Is there room to mill it down enough to get it above 10:9:1 say like 11:1 or higher?
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Konnie the Goat
01-21-2010, 11:07 AM
63cc's on a .045 gasket gets you 11.61:1. 66cc's on .045 gasket gets 11.1:1
with the l92's being a thin deck, im not sure id go down too far on them. .035" of squish is acceptable.
I never milled one down far enough to say for sure, but 63cc's would be a .040 mill, maybe .045.
Stock: 70cc
-.010: 69cc
-.020: 67.5cc
-.030: 66cc
What does this mean? It means on an LS2, you need to mill the heads .030", and run a .055" gasket to keep 10.9:1 compression. the stock LS2 heads are 65cc, and the stock gasket is .060" (im pretty sure on that gasket, but someone correct me if im off). With a stock .060 gasket and 66cc milled L92's compression is 10.77:1.
-------------------------------------------
Konnie the Goat
01-21-2010, 10:44 AM
stock LS2, unmilled l92's (72cc), .055 gasket= 10.17:1
with a .030 gasket, 10.78:1
You also then have a Piston to head clearance of just .020", as most pistons are .010" out of the hole from the factory. Thats an awful tight squish area, and will hurt power and emissions.
In short, mill the heads.
--------------------------------------------------------------------------------
Stranger808
01-21-2010, 10:47 AM
Is there room to mill it down enough to get it above 10:9:1 say like 11:1 or higher?
--------------------------------------------------------------------------------
Konnie the Goat
01-21-2010, 11:07 AM
63cc's on a .045 gasket gets you 11.61:1. 66cc's on .045 gasket gets 11.1:1
with the l92's being a thin deck, im not sure id go down too far on them. .035" of squish is acceptable.
I never milled one down far enough to say for sure, but 63cc's would be a .040 mill, maybe .045.
