LQ9 daily driver build
Thread Starter
Teching In
Joined: Dec 2019
Posts: 26
Likes: 6
From: Zephyrhills, Fl
LQ9 daily driver build I finally pulled the trigger on an engine for my 99 2 door 2 wheel drive Tahoe, an 02 LQ9. This is our 3rd vehicle/backup, so I have to keep it semi mild so that my wife can still drive it. So far my plans are mild, a set of long tube headers(1 3/4", spun metal cats, and a single 3" tailpipe), tbss intake, 92mm dbc TB, 36 lb/hr injectors(not sure the 30 lb/hr tbss ones will be enough), cam swap, and probably a set of 1.8:1 comp magnum roller rockers(I know they're not needed and won't make much difference, but I'm a HUGE fan of friction free HP).
This will be my 1st LS build, so I have a few questions. It will be used for daily driving, so 3.73 gears in a 14 bolt, a 29-30" tall tire, 4l80e trans, some MPG's, and a relatively smooth idle with good street manners(no lope with smooth power transition).
MY big questions right now are;
1. The stock C/R is 10:1, how much higher could I go, and still be able to run 87 octane fuel or is it already at the limit?
2. I've heard the 317 heads combustion chamber isn't the best design, would going to a set of 243/799 heads make a big enough difference to justify for a mild street engine?
3. Who do you recommend for a camshaft? I have always used Comp in the past, but I have heard they're not a go to place for LS engines.
4. Anything I'm overlooking?
As always, any help is greatly appreciated.
This will be my 1st LS build, so I have a few questions. It will be used for daily driving, so 3.73 gears in a 14 bolt, a 29-30" tall tire, 4l80e trans, some MPG's, and a relatively smooth idle with good street manners(no lope with smooth power transition).
MY big questions right now are;
1. The stock C/R is 10:1, how much higher could I go, and still be able to run 87 octane fuel or is it already at the limit?
2. I've heard the 317 heads combustion chamber isn't the best design, would going to a set of 243/799 heads make a big enough difference to justify for a mild street engine?
3. Who do you recommend for a camshaft? I have always used Comp in the past, but I have heard they're not a go to place for LS engines.
4. Anything I'm overlooking?
As always, any help is greatly appreciated.
On The Tree
Joined: May 2002
Posts: 151
Likes: 3
From: So Cal
Very cool....another Tahoe repower. I think that's the 4th one this week.
Do you have to computer swap the platform?....so no BCM issues, that's cool.
I don't think you'd need a 4L80, a built 4L60 would work fine to 550hp NA and it would be quicker...IMO.
I always run premium, but I think 10.1:1 is right there.
Cam.....depends on use, always a big question. Small cam for torque low rpms, bigger for more HP up high.
Overlooking? Always.....but that's part of the fun.
Here's an interesting cam I saw the other day. Stock LQ9/317s with TSP VCM cam
Good Numbers, Good torque @ 1500, almost stock idle, stock converter cam....for wife.
Check out that Dyno Lab.
2wd? Have you considered a 5speed? But probably not for the wife.....but sounds fun!
There's a guy in sugarloaf Mnt (about an hour from you) with a big 6.0 Tahoe and factory 5 speed.
Do you have to computer swap the platform?....so no BCM issues, that's cool.
I don't think you'd need a 4L80, a built 4L60 would work fine to 550hp NA and it would be quicker...IMO.
I always run premium, but I think 10.1:1 is right there.
Cam.....depends on use, always a big question. Small cam for torque low rpms, bigger for more HP up high.
Overlooking? Always.....but that's part of the fun.
Here's an interesting cam I saw the other day. Stock LQ9/317s with TSP VCM cam
Good Numbers, Good torque @ 1500, almost stock idle, stock converter cam....for wife.
Check out that Dyno Lab.
2wd? Have you considered a 5speed? But probably not for the wife.....but sounds fun!
There's a guy in sugarloaf Mnt (about an hour from you) with a big 6.0 Tahoe and factory 5 speed.
Thread Starter
Teching In
Joined: Dec 2019
Posts: 26
Likes: 6
From: Zephyrhills, Fl
I already did an 0411 PCM swap on the 5.7l in it so that part is handled. Unlike most out there, I will be reworking my factory harness to hook up to the LS instead of butchering it to put a stand alone harness in it. Wiring shouldn't be an issue for me as I did my 95 Duramax/Allison Suburban swap back in 09 and fully integrated it into the stock harness. I will be doing some towing, so that was why I opted for the 4l80e(already bought a 00 out of a van). I was actually looking at the BTR torque cam as it made more power than stock on a 5.3l, and had a pretty decent top end to it. I figured with a set of 1.8:1 rockers it would work well in the 6.0l. I know if you put 243 heads on the LQ9 you essentially have an iron block LS2 engine, but I've heard they don't run well on 87 octane, that was why I was asking about C/R.
On The Tree
Joined: May 2002
Posts: 151
Likes: 3
From: So Cal
Yeah, I went through the same scenarios on piston/head/cam combos for a light but fun 6.0 build
From my unscientific analysis here are the C/R combos I considered.
1. 6.0 with LQ9 pistons and 317 heads was 10.1: 1 (reg gas OK)
2. 6.0 with LQ9 pistons and 234/799 heads was 10.9:1 (prem gas required)
3. 6.0 with LQ4 pistons and 862 heads was 10.5:1 ish (premium gas recommended, but can scootch by with 87 and less timing)
machine shop told me they shave .004 of the heads when they resurface, so that may bump compression up a tad.
Was also looking at the BTR torque cam or Summit tow cam. Both are low lift cams and don't need dual springs....Sound and drive stock.
Then I saw that VCM cam with the 317 heads and it made 370+lbs of engine TQ at 1500 rpms. Its a high lift cam that needs dual springs, but has a little lope too at idle for sound effects.
From my unscientific analysis here are the C/R combos I considered.
1. 6.0 with LQ9 pistons and 317 heads was 10.1: 1 (reg gas OK)
2. 6.0 with LQ9 pistons and 234/799 heads was 10.9:1 (prem gas required)
3. 6.0 with LQ4 pistons and 862 heads was 10.5:1 ish (premium gas recommended, but can scootch by with 87 and less timing)
machine shop told me they shave .004 of the heads when they resurface, so that may bump compression up a tad.
Was also looking at the BTR torque cam or Summit tow cam. Both are low lift cams and don't need dual springs....Sound and drive stock.
Then I saw that VCM cam with the 317 heads and it made 370+lbs of engine TQ at 1500 rpms. Its a high lift cam that needs dual springs, but has a little lope too at idle for sound effects.
On The Tree
Joined: May 2002
Posts: 151
Likes: 3
From: So Cal
heres a milling 317 heads thread from LOL 10 years ago that might help.
https://ls1tech.com/forums/generatio...illed-cam.html
https://ls1tech.com/forums/generatio...illed-cam.html
