19GT92 Posted September 14, 2006 Report Posted September 14, 2006 hey guys i am planning on doing a n/a build up like what john89le did over on club gp and i was wondering does anyone have the specs of the lho heads and the lg5 heads i want to know which one is the better head so i can sued them on my engine build up cause i alread have one thrid of the parts picked out but the heads are my next step please any advice will help Quote
Brian P Posted September 14, 2006 Report Posted September 14, 2006 um... The 2 heads are essentially the same, save for a small difference in the area of the chamber between the valves. However that isn't LG5 specific as I've pulled apart '88-90 2.8/3.1 N/A's with that same exact casting. As to which is better? They're gonna be the same, but the LG5 style heads will knock the compression ratio down about 0.1. What parts do you have? I remember jon89le's engine having similar components to the 3.1 I built a few years back. Gen-1 3.1 TRW pistons for the high compression ratio (like 11.5:1), crane H-272 cam, etc Quote
19Cutlass94 Posted September 14, 2006 Report Posted September 14, 2006 GM used an AUX mounted turbo on the 3.1's. Basically that means that the 3.1heads and the 3.1turbo heads are the same. Quote
19Cutlass94 Posted September 15, 2006 Report Posted September 15, 2006 With 3500 valves and LS1/LS6 springs. Quote
mfewtrail Posted September 15, 2006 Report Posted September 15, 2006 I would not waste the time/money to build a "NA" 3.1. You should consider swapping in a 3400 in place of your 3.1, you'd gain 30-40hp over your current engines output depending on what year 3400 you purchase to swap in. You could always build up the 3400 later and make even more power...Jon's engine is only making about ~170hp for what it's worth(judging by his 1/4 mile trap speeds). Quote
Brian P Posted September 15, 2006 Report Posted September 15, 2006 ehk FWIW I ran a high 15 with my old 3.1 I built....granted Jon's isn't the same. But it could move. Just not as good as a 3x00 Quote
19Cutlass94 Posted September 15, 2006 Report Posted September 15, 2006 Even with a built up n/a 3400, so can only go fo far without boost. Quote
1QUICKHATCH Posted September 22, 2006 Report Posted September 22, 2006 I am working on porting a set of 3.1 heads for my lumina. I have got the flow #'s close to what the 3400 heads are in the lower lift range. should have some before and after dyno #'s as well as track times next month! Quote
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