98_1LE

iTrader: (17)

Bore: 3.905
Pistons: JE with -2cc valve releifs
Heads: 59cc chambers
Stock con rods and stroke. Block not decked, and heads not milled.

TeeKay

Here's a neat place to look for a lot of engine calc's (CR is little more than halfway down):

http://www.ondoperformance.com/calculators.html

Stock gasket is .053/.054, compressed - some aftermarket ones are .041 compressed IIRC
Deck height is .001 to .007 (piston down in the hole) - .007 most common
Stock stroke is 3.622
BTW
Stock rod is 6.098 long
Stock piston compression height is 1.34
Stock deck height of block 9.255
Stock crank throw+rod+piston compression height = 9.249
Calculated stock deck is .006

The calculator shows 10.77:1 for .007 deck - 10.93:1 for .001 deck.

HTH

98_1LE

iTrader: (17)

Thank you, that is exactly what I was looking for.

Beast96Z

iTrader: (21)

Actually it is usaully about.005-.007 OUT of the hole on LS-1's. You would be at 11:1 with stock pistons, so I'll venture to say in the 10:8-10:9 range with -2cc valve reliefs.

Cricket99SS

Yeah if you search around here you will find most people measure the piston out of the hole some.

Depending on what gasket thickness you end up with, you should be at something around 11:1, should be great! That's gonna be a slick motor when your done with it man, it's just too bad the old one had to let go.

Check out the Ross Pistons compression ratio calculator. Pretty simple to use and mess around with different options.

http://www.rosspistons.com/calculator.php

TeeKay

You know, I just posted this to Gomer. Not arguing, just trying to figure this out! How do you figure "out of the hole"? The stroke + rod + piston compression height nominal dims add up to 9.249. The quoted stock block deck height is 9.255. That puts the piston .006 down. Is the block deck really 9.242 (.007 out)? .007 out to .006 down is .013 diff (quite a bit). Huh? Whazzup?

Scott Turvey

Well, from what I've seen, all the aftermarket piston manufacturers make the LS1 pistons like everything else, that is they will be "in-the-hole" or at-deck-height at best. I've talked to JE, Mahle, CP, and Ross about this, and they say they just haven't bothered to set-up to make them the way the factory does (OUT of the hole). I'm not saying this is a good answer, just repeating what they've told me.

BTW, because of the piston "losing" those few thousandts by not being made "right", every C.R. printed on their documentation actually calcs low. To wit, I recently went through this crap on a set I ordered for a customer that wanted 10.5:1, but the actual CR was more like high 9's when we cc'd everything. Also, it appears few piston manuf's add the space from the top of the piston edge to the top of the first ring when they calc C.R.'s. The solution was to tell them the dome shape/volume I wanted so they wouldn't have to think.