Need help determining compression ratio
TECH Apprentice
Joined: Jan 2004
Posts: 337
Likes: 0
From: Frisco TX (Dallas Area)
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
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
Last edited by TeeKay; Apr 10, 2004 at 10:33 AM.
Originally Posted by TeeKay
Deck height is .001 to .007 (piston down in the hole) - .007 most common
On The Tree
Joined: Oct 2003
Posts: 128
Likes: 0
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
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
TECH Apprentice
Joined: Jan 2004
Posts: 337
Likes: 0
From: Frisco TX (Dallas Area)
Originally Posted by Beast96Z
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.
Launching!
Joined: Mar 2003
Posts: 250
Likes: 0
From: Oceanside CA
Originally Posted by 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?
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.
