LQ4 Compression

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Stepside_fever95

I'm Awesome
Joined
Dec 16, 2013
Messages
1,212
Reaction score
868
Location
NC
I have a 1999 Suburban with a 2005 LQ4 that I'm planning on doing a cam and head swap on. The cam I'm going with is the Texas Speed stage 3 high lift truck cam. Specs are 216/220 .600"/.600" 111 lsa.
I have a set of 799 heads I'm going to use and am reading mixed answers on different forums about the compression ratio using this head on a stock bottom end LQ4 with the stock .053" head gaskets. What will my compression ratio be if I install these heads without milling using stock gaskets?
Will using .040 Cometic gaskets get my compression to at least 10.5:1? I plan on running 93 octane as well.

Sent from my SM-S102DL using Tapatalk
 
Last edited:

99burbK2500

I'm Awesome
Joined
Oct 23, 2017
Messages
118
Reaction score
104
Location
North Lewisburg, Ohio
the issue with taking a guess at this is that ls engines piston to deck tend to change. mines is at 0 but most seem to fall around .007 out of deck. some as high as .011. mines a mutt tho too so that makes a difference. collect some info on the heads combustion chamber sizes from your current head to the 799 and use a compression ratio calculator. summit racing web site has one. gasket bore size makes a difference too. I have the low lift in my 5.3 with 10.56:1 compression and a .040 quench height on a 112lsa and it runs strong. I would get you a thinner head gasket and bump the compression ration up some and tighten the quench height up to around .035-.040. she will like that.
 
Top