I'm trying to figure out DCR of a stock LQ4 motor.

I put the numbers into my calculator and came up with 8.34:1, does this sound about right?

4.00 bore
3.622 stroke
72cc heads
.054 gasket
4.00 gasket bore
-.01 piston to deck
8cc piston dish

I guess on the .006 cam specs
258 intake
264 exhaust
114 LSA

6.098 rod length


This gives me 9.37:1 static, 8.34:1 dynamic

Someone double-check my work?

 

Thunder,

Hey, sorry it took so long for someone to get back to you but I've been doing the same calculations for my 4.8, trying to predict the effects of the GT2-3 cam. Anyway, I found a Visual BASIC calculator somewhere on the web written by a guy named Pat Kelley, and it's pretty easy to use and seems to give reasonable sounding numbers. So I plugged in your numbers as you gave them and came up with a SCR of 9.37477 and a DCR of 7.59101. For comparison my 4.8 w/ stock cam shows SCR = 9.46003 and DCR = 7.67939. I then checked your values as best I could in "How to Build High Performance Chevy LS1/LS6 V8's" by Will Handzel, and he lists the 6.0L chamber volume as 71.06 CC. Plugging in that number and tweaking the gasket thickness to get a SCR of 9.40418 (as close to 9.41 as I can get) gives a DCR of 7.61494 (gasket thickness = .057). From what I've read, a DCR of around 7.6 or so sounds about right for an engine designed to run on 87 octane gas. Hope this helps.