I can get an 345 hp for $2200 or get a 300hp for $1400. Whats the difference in specs between the two besides hp? I planning on new heads and cam either way. Just want to know which one to get. Don't want to waste money if the heads and cam are the only difference of the two.

 

The actual difference is in piston design. The 345 hp LQ9 engine has different piston which yield a higher compression ratio of 10.0:1 v.s. the 300 hp LQ4 which has a compression ratio of 9.4:1. I believe they both have the same heads. LQ9 has thicker rods, however the LQ4 has proven to be very strong for most people. You will probably want to make sure the LQ4 is from a 2001 and up year model. They should have aluminum heads and will work with your 4L60E trans. Since you have a supercharger I would get the 300 hp LQ4. (lower compression)

 

Thanks VortecSierra.

 

LQ4 is also rated for 325 in a Sierra Denali/Yukon/Yukon XL and Suburban. That extra power was gained by tuning on GM's part. The LQ4 is really detuned from the factory.

 

Whats the chamber size on the 6.0 heads? Can 5.3,Ls1, and Ls6 heads bolt right on without modifications?

 

Texas Speed has some stage 2.5 5.3 heads as a package deal and was wondering if they would work on a 6.0.

 

They will work just check the combustion chamber size to make sure they aren't going to bump the compression to much, especially with your blower. Definately check that.

The 6.0L heads have 72cc combustion chambers which are about as big as they get on the Gen III engines except for a few aftermarket ported heads which can be a little bigger.

The piston and rods are definately different between the LQ4 and LQ9. I think BigTex has some nice pictures of them side by side. Both have been proven to take alot of abuse though, the LQ4 has dished pistons though so they would work better with your blower.

Check with Richard at www.proheads.com also and see what he has available right now. Moregrip got some nice heads from him for a decent price.

 

i work at a dearlership in new orleans and an m motor is 10.4 and a u motor witch comes in 2500 series truck is 9.4 compress i dont really no y every body thinks its a "10.0" compression, any way yes the pistons are diff. but it doesnt really matter, you said you where getting heads, depending on who you get them from, shaving the heads you can go up till .30 thosands whit out any trouble, any thing after that angle milling is nesscary, eiter motor is good, i no of a U motor,9.4 compression that went 12.64 in fair to warm weather, its all in knowing wat ur doing, cam, ur truck is 4200 single cab 4700 extended cam, so you need a really torguey cam that will pull the hole way threw and not fall off, again heads you can put big *** exhaust ports cus you will lose torgue there too, and tuning, tuning is every thing if your sacared to shift high you will never run good numbers..........and plenty more...

 

12.64 in a extended cab at that and was torn down today to be put in a crew cab, with cnc ported heads that will fly, and wonder cam,,,,,,,,ALL MOTOR, and everyday driver

 

VIN digit for an LQ9 is not M, its N.