sorry this is gonna be kinda long...

i bought my '04 Silverado ECSB back in august and have since become obsessed with the GMT800. the gen-III chevy small block simply fascinates me, its a hot rodder's dream.

my plans are to build my truck how i wish the factory would have.

i couldnt afford an SS or Vmax/VHO so im eager to swap in a 6.0. problem is, there are so many options and im relatively new to the game. rather than junk up the forum with a buch of different threads, id like to make one thread for most/all of my questions or concerns. ive been doing alot more reading then posting so far on pt.net, and i must say the knowledge here is astounding. i had to get into the game sooner or later.

my truck is driven daily but will see frequent track duty, and i know i will be breaking stuff. im keeping my 5.3 completely stock to keep as a spare after the swap.

so here's my first dilemma: LQ4 or LQ9? i know the LQ9 has different heads/pistons for a higher CR, but are they really worth it? you could cam an LQ4 and have close to the LQ9's stock 345 hp. im shopping around for a 6.0 and would like to know if there any difference in the potential of each motor.

again, sorry for the long post and n00b questions, but youve gotta start somewhere

 

The lq9 has the same heads/rotating assmebly as the lq4 except flat pistons to bring the compression up. If you are looking for a new engine I would put a 6.0L LS2 in and use the adapter harnesses. You will have more compression than the lq9 and the ~100lb weight savings with an aluminum block.

 

Remember if you use an LS2 you have to find one with a 24x reluctor wheel. the LS1 PCM has to have this to function, most LS2's use a 58x reluctor wheel. The only ones i know of is the 2006 GTO

 

IMO I wouldn't do this just because you can find a good used lq4 for around $1000 and a lq9 for just a bit more(if you look around). I have yet to see an LS2 for anywhere under $3000, and while I'm not possitive, I would imagine going from a gen III engine to a gen IV isn't quite a direct swap.

So if you save $2000 by going with a lq4 then you can put that money towards a good set of heads and have a better setup than a stock ls2.

 

i would like to stick with a truck motor, but thanks for the LS2 ideas, guys.

so if i plan on upgrading the heads there's really no reason to go for an LQ9. that's the confirmation i was looking for at the moment, thanks randomhero

 

next question/concern:

i plan on running an STS kit later on down the road. i know then ill probably need to have the bores honed with a surface plate before i install any aftermarket forged units. i might as well do this before i install the motor so when im ready for FI i wont have to tear the motor down again. i understand the factory cast-aluminum eutectics are good for around 500 horsepower, but it makes more sense to install forged pistons with the initial build.

since im planning on upgrading the heads and pistons, there's no real reason for me to search for an LQ9, as these components are essentially the only ones that differentiate the LQ9 from the LQ4.

what about the bottom end? i know of a few people who have made 650+hp with a stock crank, so really the only reason to replace it would be for stroking purposes, correct?

 

Whoa I never said that. I'm not saying that is or isn't true....that's beyond my knowledge.

I was just saying that you should pick up a lq4/lq9 over an ls2.

The lq4 seems to do better with forced induction
The lq9 seems to do better n/a

That is of course in stock form and the reasoning lies behind the compression ratios.

 

The heads are the same between the LQ4 and LQ9 -- exactly the same. As is everything except the pistons and the rods.

LQ9 = 10.1:1 CR
LQ4 = 9.4:1 CR

I actually disagree on the FI thing for initial setups. If no more than 12-13psi is cool with you, the LQ9 will make more power. If you want more boost than that, then the LQ4 is the better answer.

From a pocket book point of view, Random is dead on -- the LQ4 will be cheaper.

If you are going forged anyway, LQ4 vs LQ9 is a moot issue and get the LQ4 (because it's cheap)

 

if you put stock 243s on your 6.0
Exact Quote from Richard at WCCH
10.5:1 cr is achievable with some milling. Have the 243's milled between .025"-.030"

BTW ask him any question you have about using what heads, and what you'd like out of the motor and such. he's willing to answer any questions that you have.

 

I believe that the newer lq4 and lq9 have the same rods but the older lq4 motors had different rods, I am not sure the years they changed. somebody else will have that info.