What's the difference between them and if one of them is better for an upgrade from a 5.7 to 6.0L for a Procharged car?

 

I believe the only difference is the pistons. The lq9 is higher compression. The lq9 is the "high output" version with more horsepower stock.

 

The heads have diff cc's I believe.

 

i thought the LQ4 had a smaller bore? I'm just a newb, though. I don't have any idea.

 

can i use the L92 head + L76 intake on these ??
or is the LS6 intake + head my only choise for a cheap factury built ?

 

Compression is the difference. I am not sure how they changed it but I would assume it would be the heads.
I think you need a 4.0 inch bore to use the L92 heads, Hot Rod or Chevy High Tech performance just did an article on it. They used a 6.0 liter block.

 

https://ls1tech.com/forums/showthrea...q9+differences

https://ls1tech.com/forums/showthrea...q9+differences

 

i thought the LQ4 / 9 comes stock with the 4.0 bore ... no ?
some people bore it to 4.03 or even 4.08 ....

 

It does. I was just putting it out there for the guy.

 

Wow, a lot of misinformation here.

LQ9 and LQ4 are identical, except for the pistons. The LQ9 has flat top piston to reach 10.4 or so CR, while the LQ4 has dished pistons to reach 9.5 CR. Both use the same heads, 317 with 76cc chambers (which flow similarly to LS6 243 heads). The bore is 4.00" and the stroke is the same as an LS1 3.89". For a boosted application, you would be better served using the LQ4, unless you are staying at 4-6 PSI (then you can go with the LQ9).

Oh, and yes you can use the L92 heads on an LQ4/9.

 

LQ4 has shorter head bolts

 

Nope! Heads bolts are the same for all Gen3 engines, around 2003 GM changed the length to be the same. Earlier engines had two corner bolts shorter then the rest.

 

your right, but most LQ9's that are around (unless you buy a new GM one) were built before 03.... mine had the short corner bolts... i think pretty much all LQ4's were built after 2003 and have the different head bolts.

 

Ok, if the blocks are the same, why you prefer one (LQ4 for boost up to 6 psi) over the LQ9. LQ9 will hold more boost?

 

LQ9 was introduced in 2001 with the 317 aluminum heads (replacing the LQ4 Iron heads).
LQ4 was introduced in 1999 with iron heads.
Don't believe me, do a search ... this is how I found out about the 2003 change, plus I have personal experience with this (head bolt) issue (see sig).

With boost, you want a lower compression ratio to reach higher boost levels. Both will take the same amount of power, but with the 10.4 or the LQ9, you will be boost limited. The connecting rods can only handle so much combustion chamber pressure. Plus you read it wrong.

LQ9 (10.4) = 6 PSI safe boost limit
LQ4 (9.5) = ~10 PSI safe boost limit

 

Ok, I just got it. I was thinking about the block alone (one stronger than the other) and I wasn't considering their stock pistons.

 

actually 12secSS, the facts are:
stroke 3.622
LQ4 compression 9.4
LQ9 compression 10.0
both have 72cc heads

So, buy either and upgrade the pistons and at least the rod bolts.

 

Thanks for your time and info.

 

Speaking of mis information, the stroke of an LS1 is 3.622 inches. The bore is 3.89 inches (for an LS1). The LQ4/9 have the same stroke and a 4.0 inch bore.
AJ

 

Still learning a lot. Thanks, Mike (PR).