wicked383lt1

Hey guys so I'm having a bit of trouble finding out what head gasket I need with my Lq9 build. So far what I have is a 05' Lq9 with a TSP Ms3 cam package. I've been reading and see that the 243 heads will raise the compression to high. What can i do to lower the compression and what head gasket will i need?

HCI2000SS

iTrader: (2)

You've been reading that stock 243's will raise the compression to much, and if so how much compression are we talking here?

wicked383lt1

11:1 from what I've read and would have to run high octane fuel. (higher than 93)

KCS

iTrader: (20)

Use 317 heads instead. The chambers are about 71cc versus the 64cc chambers in the 243 heads.

Use this to figure out compression ratios:
http://wallaceracing.com/cr_test2.php

HCI2000SS

iTrader: (2)

11.1 with 93 is fine. Not sure who told you that

wicked383lt1

So I can make more power out of the 317's over the 243's? I may use spray in the future. So this wouldn't pertain to me?
Again it's just what I've been reading.

Ernie W

iTrader: (1)

If it's a stock lq9 bottom end with 243 heads it would basically be a iron LS2 as they use the same pistons. I'm putting a set of 799 heads on my lq4 and I've "read" the compression should be around 10.4-10.5:1 but I'm not completely sure.

wicked383lt1

Yea it's a stock bottom end. That's also what I was thinking. So this what I found. Now some people say to use a different size head gasket due to the compression and PTV clearance. LQ4 debuted in 1999
Displacement was/is 6.0L
1999-2000 had iron heads
1999-2000 had a crank adapter to mate the LQ4 with the 4L80 trans (not LS1 compatible)
Compression ratio was 9.5:1
Bloack was Iron

In 2001 the LQ9 was introduced
Both the LQ4 and LQ9 shared the iron block and new 317 heads (similar as the 243, but with larger 76cc chambers), hence both are 6.0L
The LQ9 had 10.4:1 compression ratio, versus the LQ4's 9.5:1
No longer did either 6.0L require the crank adapter for the trans, now works with LSx applications.
In 2004/5 6.0L recieved improved rod design

In 2005 the LS2 block was introduced
It is essentially the LQ9 with an aluminum block
LQ9 still offer with an iron block.

KCS

iTrader: (20)

Not naturally aspirated, but you may with nitrous. If you're worried about the compression ratio being too high, you can use the 317 head to lower it. My old engine was around 11.25:1 and it ran fine on 93 octane in the Texas summer heat, but I wasn't spraying it.

wicked383lt1

I'm not going to spray it anytime soon. So what gasket will i need to install with the 243's and what will in need to do to be able to spray the car eventually with the 243's? Will that combination of the Ms3 ,Ls6 intake,P/P Ls6 tb,circle d 3600 stall ,and 243's be the correct set up? Again from what I've read the 243's like to be rev'd up. This is my first build and I'm doing it alone. I'm just looking for proven combinations with the LQ9 and these mods.

Aaron at SDPC

I would recommend running the 243s, and use GM MLS gasket number 12610046. With a proper tune this will have no issue being pump gas friendly. The setup should be fun and run well. What will the primary use of the car be? If you plan running without spray the majority of the time I would consider swapping to a looser converter. That 3600 is going to be a bit tight for the MS3.

wicked383lt1

The car will be a weekend warrior and occasionally taken to work on a Friday. I have to upgrade the rear and the transmission before I can go to the track with it. Correction on the stall, it's a 3800.

Aaron at SDPC

Sounds like it should be a fun setup for sure, and that 3800 stall speed converter will definitely work a little better with the setup.

wicked383lt1

Thanks a lot guys for all the help

rpturbo

iTrader: (47)

Sounds like a killer setup for just a basic setup. Thats what I was going to do with my LQ4 before I 100% decided I had to have boost, so I went with a turbo cam.