xr4tic Posted July 2, 2013 Report Share Posted July 2, 2013 I've been researching ported heads, and I've seen a couple of ported 243 heads pop up in classifieds, but they've all been milled. I plan on keeping my truck NA and I use my truck like a truck, which means it needs to be able to haul and tow. What's the highest CR I can get away with on pump gas (93 octane, but ideally be able to run 91 octane if I'm out of state hauling something) Bonus points if someone can tell me the head cc size to achieve that CR. Quote Link to comment Share on other sites More sharing options...
GI.SS Posted July 3, 2013 Report Share Posted July 3, 2013 If towing a high compression ratio will cause knock. You will need to answer a series of questions to get a better idea of your build. I'm sure someone will chime in... I'd suggest running a standard 243. But that's just me Quote Link to comment Share on other sites More sharing options...
BLNAWAY Posted July 4, 2013 Report Share Posted July 4, 2013 I wouldn't go over 10.5:1 personally Here's a lil reading for ya: http://lsx4u.com/lsxinfo/heads.html Quote Link to comment Share on other sites More sharing options...
xr4tic Posted July 5, 2013 Author Report Share Posted July 5, 2013 Thanks guys, you've confirmed what I was kind of thinking. Sounds like I'd be better off having a set of 317 heads ported and maybe milled a bit, even a set of 243s would push the CR to ~11:1 Quote Link to comment Share on other sites More sharing options...
Krambo Posted July 5, 2013 Report Share Posted July 5, 2013 DCR is what you should be comparing rather than SCR. A cam profile, overlap in particular, can allow for high compression ratios on pump gas. FWIW, I ran 11.5 SCR on pump gas (93 RM Octane) without issue. I have seen 12's SCR on pump gas in a LSx engine as well. A set of 243's on a stock LQ9 bottom end would be a nice combo IMHO. The right cam / converter combo would make for a sweet N/A set-up. Quote Link to comment Share on other sites More sharing options...
JC03SS Posted July 5, 2013 Report Share Posted July 5, 2013 Im gonna go with a set of ported and polished 243's and if im not mistaken should still be less than 11. ls7's are 11.1 if im not mistaken either. Quote Link to comment Share on other sites More sharing options...
12'SROCK Posted July 24, 2013 Report Share Posted July 24, 2013 I dont tow but have 8.84:1 DCR 11.32:1 SCR. I run pump gas 91 here in Cali. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.