Mavn

iTrader: (3)

Been trying to figure out what the compression ratio will be with a lq4 with stock .051 6.0 head gaskets and a set of stock 706 heads ?

Lq4 compression ratio with 317's with a 71cc chamber is 9.6:1

706 heads are exactly 10ccs less . 61cc .

Why can I not fugure this out lol

Am I just stupid today ?

It would go up to around 10.5:1 right or am I way off

G Atsma

Check out Summit's Compression calculator. Easy to use (even I figured it out lol).
Using that, I come up with 10.72:1

omc8

iTrader: (7)

Stock LQ4 cr is 9.4 : 1

Utinator

I came up with 11.43:1 compression with the .051 head gaskets. The LQ4/9 has flat top pistons, so there's no "piston top volume". I used this calculator: https://www.rbracing-rsr.com/compstaticcalc.html

G Atsma

Don't forget to figure the piston will be OUT of the hole .004. Not everyone knows this.

Fast355

LQ4 pistons are dished. Two different pistons and dish cc's depending on the year. The later LQ4s have GenIV rotating assemblies in them and use LY6 pistons.

G Atsma

Summit's spec page shows 6.7cc dish on LQ4 pistons.

andy burdess

omc8

iTrader: (7)

Those LY6 pistons had the same dish but with valve reliefs .They would have a slight volume difference I have never checked the compression height of the two.but they have to be very close in spec .if not the same .

matts01z71

I am about ready to start my lq4/706 top end, i used this. http://www.wallaceracing.com/cr_test2.php

4.0
3.622
61.00
6.7
.045
4.045
.004
10.5 roughly