i've done a search and read that running stock 4.8/5.3 heads on an lq4 would raise the compression between 10.7-11.0 and not flow as well do to the smaller valves. so what if, the 4.8/5.3 heads were ported and polished and had bigger valves? i don't care if the commpression higher, i just want to know if it will still perform well, say mid 12's.
i have a
2x4 scsb
full exhaust, no cats
4.10's
4l60e w/2800 stall
and some more stuff
i also want to run a cam in the 236 112 area

 

Aint higher compression more hp.

 

Yep higher comp is more HP, but at the same time you have to be able to flow the air/fuel to make the power. I have done a lot of research on this, and you can get into the 12's with this combo, check Litredevil. However what I want to know is if the extra compression making more power in th elow end will make up for the lost power in th ehigh end. Im personally thinking of finding some LS1 heads and try to get the best of both worlds.

 

According to my calculations you'll end up with a bit over 10.7:1 cr with the 4.8l heads. Yes it will run very well if you can get the airflow up with porting and bigger valves. If you can get the cores cheap enough, the LS6 heads make a great swap. They woiuld need some milling to get the chambers down to 61cc.

Good luck,

Richard

 

well...i think im going to find some 317 heads, have them worked shaved .030. that will get my compression up a little for the dished pistons

 

why not just use #241 LS1 heads ???

10.4 CR, 2.00"/1.55" valves, and a 66.67cc chamber.......it's certainly worked for me

 

10.4:1...now what if i shaved them a little? maybe i'll find some 6.0 heads. i have a brand new never used 6.0 intake. that would match up good

 

I recommend using the Ls6 #243 heads with the 64-cc combustion chamber if you want to up the compression a point on the LQ4. The ls6 heads flow a little better than the ls1 #241 heads. This combo will be similiar to the 6.0 engine in the ls2 05 c6 vette. I dont recommend this combo on an Lq9 because it allready has a 10:1 with the 317 heads and compression will be too high, which would require changing out pistons. This combo with a nice cam, tune and all the boltons can make some great power, I would even be willing to bet around 375hp and 400tq RWHP. I have been researching this, because this is what I plan on doing.

 

I've done this with the #241 heads....your power estimate isn't too far off, I finally made it to the dyno this summer, with a ****-poor tune and 108º outside temps put down 356/394. I'd probably have seen a little better with #243 heads but the price different wasn't worth it to me. with a good tune I hope to see 375/415

 

ive been thinking of doing the swap to 4.8 heads myself. good info