I am using pianoprodigy's dcr calculator and it seems like the compression numbers it is giving me are high. It comes up with 11.56:1.

http://www.bowlingss.com/DownLoads/D...okup%20LS1.xls
these are the numbers I'm putting in.
59cc camber
.04 head gasket
-1.5cc fly cut pistons

this calculator comes up with 11.2:1
http://www.c5frc.com/calculators/Com...Calculator.htm

any one know which one is correct?

 

What engine do you have. An Ls1, or an Ls2. Stock bottom end or stroker.

 

I punched in the numbers for an LS1 and with what you supplied I came up with a round-about number of 11.57:1

 

stock ls1 bottom end

 

I got 11.3

 

whats the deal with all the different numbers?

 

The cam plays a pivotal roll in the equation. What cam are you using?

 

The difference in the numbers are from what we think the pistons are coming out of the hole I believe. Some come out a little more than others and some dont. I used .007 out the hole.

 

try this one and put a negative value for piston deck height -.007

http://www.rbracing-rsr.com/compstaticcalc.html

 

seems your #'s are right but it would be positive for a flycut. 1.5
-0.007 DH
I'm getting 11.58:1 SCR

 

The 11.56 I got the first time was with 2cc pistons. When I use pianoprodigy's and the one predator suggested, I get 11.64 with 1.5cc pistons.

So the final numbers on the set up are:
prc 2.5 ls6 heads w/59cc chambers
-1.5cc flycut pistons
.04 cometic
ms4 111 +3

all of this gives me 11.64scr and 8.65dcr

 

Sorry to hijack, just wondering what the highest CR to run pump 91 or 93 gas is?

 

there are alot of variables that go into to it like, combustion camber, quench, tune, ect. Most of the higher numbers i see are in the 8.6-8.8 range.

 

I like this one too.
Use it all the time.
http://www.rbracing-rsr.com/compstaticcalc.html

 

Guys can someone give me the stock LS1

Bore
Stroke
Deck Height Clearance

Thanks!

 

Stock LS1 measurements:
Bore: 3.8976"
Stroke: 3.622"
rod length: 6.098"
deck: -.007" (piston extends above block deck)

 

WAT???

 

He is referring to when calculating dynamic compression. IMO dynamic compression is the valuable number you should be looking at. It will be the largest factor as to whether you can run pump gas or not. I would shoot for 9.2:1 or lower if you plan on running pump gas on this motor. Remember the number I just listed was DCR not SCR.

 

Personal taste. We like to play it safe with pump gas and keep out of the low octane table with knock retard on hot days. There are a lot of factors to controlling detonation. Not running cheap pump gas on to high of compression is one of them.

 

Can someone tell me my DCR with a 61cc LS6 head and a .053 gasket. I can only get my SCR which is 11.1, thanks