INTERNAL ENGINE MODIFICATIONS Valvetrain |Heads | Strokers | Design | Assembly

Rethinking / remixing GM OE

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Old Mar 6, 2024 | 11:34 AM
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better LS2= put a truck intake on it

Cam opinions are wild. I would like the LS6 cam for this scenario
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Old Mar 6, 2024 | 05:26 PM
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Originally Posted by arthursc2
better LS2 = put a truck intake on it
It means PUT A CHICK IN THE LINGUINE, AND ...
sorry ...

Since it's a proven fact that the LS2-truck manifold works better than the LS2-car manifold, next question is:
Where ELSE can I get an LS2-truck intake? BESIDES a GMT360 with an LS2? Because those are likely already GONE.
Now I need to figure out how to connect a physical throttle body to an LS2 truck intake. Otherwise I'll just reuse the LS-Vortec manifold I've already ...
Originally Posted by arthursc2
Cam opinions are wild. I would like the LS6 cam for this scenario.
Given that Tahoes weigh a wee over 5,000lb before anyone gets in, and that this will soon become a work truck carrying loads of construction equipment, do you still feel strongly about the LS6 cam?

Scenario 6.2L has basically become ... if I find an L92 / L9H / L94, I'm only going to try the 243-799 heads on it if I have money burning a hole in my pocket, 'cause it'd need a VVT delete and a few other things done to accommodate the 12200411 pcm. At least I'd make a few bucks selling the rectangle heads off it.

And may I ask again: What'd an LS2's compression ratio be, wearing 706 / 862 heads? 11.?-to-1
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Old Mar 6, 2024 | 05:31 PM
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Any GMT-900 truck has the same intake manifold just about.

GM didn’t use those 862 heads on any of their work truck engines. If compression was the end all be all I believe they would have.

Are you willing to put premium in your work truck?
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Old Mar 6, 2024 | 07:05 PM
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Originally Posted by shakenfake
Any GMT-900 truck has the same intake manifold just about.
That's some good news for sure! Now I just need a physical throttle body ...
Originally Posted by shakenfake
GM didn’t use those 862 heads on any of their work truck engines. If compression was the end all be all I believe they would have.
You mean, 6.0L work truck engines?
You may be right - either they got
a) LQ4 Iron heads or LQ4 / LQ9 heads (I'd swap out for my 706-862 heads ASAP),
b) rectangle heads, or
c) in the case of a 6.0L out of a hybrid, 243-799 heads.
Originally Posted by shakenfake
Are you willing to put premium in your work truck?
In NYC and the surrounding states, 91 can cost anywhere from 80¢ , to $1.60 more than 87 octane. So, no, 87 or E85 only.
I AM willing to pay a tuner to customize my Low and High spark tables though.
380ft-lb may not be doable. Somewhere between 355 & 385 horses @ 5800RpM seems feasible though.
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Old Mar 6, 2024 | 09:15 PM
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I am talking Gen IVs.

Then you do NOT want 11:1 compression. That is way too high on 87. E85 yes, 87 no.
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Old Mar 6, 2024 | 09:44 PM
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Originally Posted by shakenfake
I am talking Gen IVs.
Right, so, most likely rectangle heads, or 243-799 heads.
Originally Posted by shakenfake
Then you do NOT want 11:1 compression. That is way too high on 87. E85 yes, 87 no.
I think I get the concern about static compression ratio.
However, if I can choose the cam to limit dynamic compression, and the spark tables can be customized specifically for 87 octane, I don't see why I need to worry?

Nobody knows the LS2's power ratings (@ 10.9:1 CR) on 87 octane - except maybe GM? - and GM will never tell.
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Old Mar 6, 2024 | 10:06 PM
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Static compression will make the engine/vehicle more lively down low- yes I would do the LS6 cam

like I said tho, cam opinions are gonna be wild and there are a ton of better aftermarket options

LS6 cam is a proven performer in the truck field with big bore motors
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Old Mar 9, 2024 | 07:36 AM
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Drop in a 2001 or later Gen 3 6L (LQ4 or LQ9) is the best option. LS6 or even some of the small truck cams with 208 or less duration sound perfect for your application. If you pull an LQ4 or LQ9 from the wrecking yard watch out for cracks around the drain back holes in the heads. My original 317 heads cracked and the engine started using coolant. I wouldn't worry about swapping heads if you want to run 87 octane, clean up the 317's, refresh the springs and seals, change the cam, then roll if the engine is in good shape.
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Old Mar 10, 2024 | 03:10 AM
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If I find an LQ4 / LQ9, even if I leave in the cam it came with, it's losing the 873-317-035 heads.
Whether it gets my 706-862 heads, or 243-799 heads, will depend on what I can afford by, among other things, selling off the 873-317-035 heads.
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Old Mar 26, 2024 | 06:44 AM
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From summitracing on LQ4 with 706 heads, octane, etc. I had pm'd them about a build for torque, never seeing 6krpm, towing, etc. Also, for a non-stock cam, they recommended their SUM-8727R1 for under 6k rpm.

I like the idea of the 706 heads for the compression boost and hp/tq increase across the range. You would be around 10.5:1 compression with the factory 6.7cc dished pistons and factory .051" head gaskets. This puts you in the range of needing 93 Octane especially for towing.
Regarding heads that will allow the use of 87/89 for towing. That would be the 317's which would put you at the stock 9.4:1 with a .051" head Gasket. Also the 243's which would put you at 10:1 with .051" head gaskets. 10:1 is pretty much where we feel the limit is for towing with 87 octane.


I know I added a no OE cam. For your power range, the very earliest lq4 cam would work great. I have a 2000 chevy 2500 6.0 5spd, and it seems to run out of steam by 5k rpm, or before, especially compared to my 2006 lq4 in my tahoe.

According to what I've found, the 99-00 lq4 had a 191/190 on 114 lsa cam, and the 01-06 had 196/207 on 116 lsa. From driving mine, the 2000 feels like an old 350 sbc as far as revving and towing goes, and the 2006 engine feels fairly rev happy, but lacks a little off idle. Both engines are bone stock, with bone stock tunes. The tahoe does have e fans added, and the 2000 truck has a huge duramax mechanical fan drawing more power, but keeps the engine very cool while overloaded on the farm.

Last edited by jonnyboy; Mar 26, 2024 at 06:51 AM. Reason: Add in
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