Hi! New member here.

Has anyone researched using the LQ9/LQ4 6.0L aluminum heads for their supercharging application? The LQ9 heads are the higher-performance version of the LQ4 heads. They're basically the LS6 heads with larger combustion chamber. These would seem ideal for supercharging applications on an LS1 or LS6 engine.

The stock LS1 heads give the LS1 a compression ratio of 10.1:1. The stock LS6 heads give the LS6 a compression ratio of 10.5:1. The LQ4 (newer aluminum version) heads on the 6.0L truck engine are 9.4:1. The LQ9 heads on the 6.0L truck engine are 10:1. My information says that the LQ4 (newer aluminum version) heads will drop the compression ratio of the LS1 to approx. 9:1 which in combination with a better cam (optimized for the supercharger application) would be really great!

I want to use either the LQ4 or LQ9 for an LS1-based supercharger application (on 2002 C5 MN6 Coupe). If you're planning to run alot of boost, which I am, you're going to need to lower your static compression. This will in turn affect the low-end performance of your car when the blower isn't at the boost levels that require that lower compression. So my ultimate goal is to obtain a compression ratio that will still give ne low-end performance when the blower isn't running at optimum boost levels yet will still be low enough (compression ratio) to allow for some serious boost. The LQ9 or LQ4 heads seem to be the way to go.

Anyone doing this? Thoughts and opinions?

Any issues with using either of these heads with a 2002 Corvette LS1?
Who sells the LQ9 (and LQ4) heads? I tried finding them through GM Performance Parts, but although they have the LQ4 engine listed, I couldn't find just the heads. Anyone have the GM part numbers? Thanks!

-Keith

 

alot of guys are doing this and getting good results, post this over on the corvetteforum in forced induction/nitrous

 

I'm using them on my forged 348. You can find them for sale on the For Sale board here on ls1tech. There is usually a set or two there, prices go from 450 to 550 for them unported. A couple of our sponsors to the right have some ready to go with upgraded valves, springs, ports and chambers try patriot perf.->
J

 

Cool! Thanks for the info!

 

Watch your gasket bore if you don't weld and resize your LQ4/LQ9 chamber to match your stock bore. There should be plenty of people running this combo here.

Check the 'Internal Engine' section here also for NA setups running LQ4/LQ9's.

 

yep like mello said, i went with the 6.0 heads and the 3.905 gasket to match my bore, and the leaked, replaced them with the 4.0 bore gaskets and am ok now.

 

Thanks MellowYellow and smokinHawk!

 

I am running a set of stage II ported 6.0 heads on my motor.

 

Do you have the LQ9 or LQ4 heads?
Did you leave the combustion chamber stock at 71.06cc?
What all did you have done to get that 9:1 ratio?
Also curious to know how much boost you're able to run with that YS-Trim supercharger, if you don't mind me asking.
Sounds like an awesome setup!

Thanks for the info!

 

I have the older 6.0 heads that were 70/71 cc's stock.

Mine are around 69cc's now. I did the 6.0's for two reasons:
-higher cc
-better flowing heads at higher lift than ls1/5.3's

I am running Diamond 9:1 pistons are -8.6cc.

My setup is pulleyed up for 18-22 lbs of boost, an 8 rib setup with a 8.0 crank pulley and a 2.85 blower pulley. I would be comfortable trying for up to 22/23 lbs of boost with my MLS 6.0 head gaskets since I have a lot of other good parts in my combination like my fuel system and FAST system. Dynoing soon but mostly to dial in AF.

 

We build the 6.0L heads for boost all the time it is what I would rec. to go with on any boost application.

Nate

 

Well i bought LQ9 ( 035 castings ) unported. I need to order pistons. What size should i order 9/1 or 9.5/1 pistons. If the LQ9's have a CC of 72cc's bolting them on a stock LS1 should bring the compression down to 9.5/1? And if i ordered 9.5/1 pistons for a stock LS1 that should drop the compression down near 9.1/1 right?

 

When you order the pistons just tell them the bore, stroke, cc of the heads and desired comp. ratio and they should hook you up with the right pistons. but yes 9.5:1 pistons should drop you to 9.1:1 comp. with the 72cc heads.

 

Thanks Turbo, thats what i needed to know. Thanks again. WHen i talked to Chris from Diamond yesterday i gave him all my info. but just incase i'll check back with him today.

 

02BlackWS6 where did you get the LQ9 heads from and how much?

 

I got them from Shaun Carter (Valvegod@aol.com) for $550. Plus shipping. They came complete with valves and springs installed. Plus they were never ran. And he ships them real good so you get them in perfect shape. I've bought 3 sets of LS1 style heads among alot of other stuff like PCM's from him and he's great to deal with. Drop him an email.

 

I just got off the phone with Chris from Diamond pistons and he set me up with 9:1 dished pistons. Can't wait to complete this setup

 

There is no physical difference in the LQ9 / LQ4 head. I have an LQ9 motor in my Silverado SS, and it has heads with casting number 317. The 317 heads also come on Escalades, Denali, HD trucks, etc... All the newer (01+) 6 liter heads have 71 cc chambers and the D shaped exhaust ports similar to the LS6 head.

The difference in compression on these motors comes from the piston, not the head: flat top hypereutectic on the LQ9 VS cast dished on the LQ4. Several months back, Chris Endres wrote an article for GMHTP (also in his book, but the article came out first) saying the 035 head was preferred over the 317 6 liter head in the FI community due to its 9.4:1 CR. He didn't take into account the CR was different due to the piston, not the head, so the article was misleading at best.

Dont pay a premium for the 035 head, its the same as the 317 head.

 

I run ported GTP ST 2 6.0 head on my Turbo car.
I got them all done threw Speed inc>>><>>>>>>>>
Call Tom, he can hook you up good. Heads flow great #'s.
Good luck

 

Everything I have heard is that the LQ4 and LQ9 heads are identical. The main difference between the motors is the pistons. LQ4 had dished cast pistons, the LQ9 has flat top hypereutectic cast pistons. BigTex has researched this and the castings on the heads have the same numbers. The compression ratio difference and tuning for Premium gas are what differentiate the two.