Cam / Head re-selection for 6.2 LS3
Thread Starter
Teching In
Joined: Mar 2008
Posts: 5
Likes: 1
Cam / Head re-selection for 6.2 LS3 hi
I am considering changing the cam or heads in my truck to improve the performance as it is lazy on low RPM but it loves to rev high. the truck is used in sand dunes and I am using around 93 octane fuel.
what step do you suggest to start with:
- milling the heads and install thinner gaskets to raise the compression
- change the cam (any suggestions?)
- change to CNC ported cathedral 799 heads
below are the specs:
1986 GMC K15 4x4 short-bed pickup
6.0 LQ9 block bored to 6.2
6.2 L92 stock pistons
821 LS3 heads ported by Lloyd Elliot + milled 0.020"
GM MLS 0.051 head Gaskets
CR around 10.7
222/230 .598"/.598" 112 LSA custom camshaft
PSI1511 Springs
L92 6.2 Stock intake manifold
92mm DBC WARR throttle body
1 7/8 long tube headers
3 inch dual exhaust w. H-pipe
SM465 manual gear
3.73 differentials
33" mud tires
thx
I am considering changing the cam or heads in my truck to improve the performance as it is lazy on low RPM but it loves to rev high. the truck is used in sand dunes and I am using around 93 octane fuel.
what step do you suggest to start with:
- milling the heads and install thinner gaskets to raise the compression
- change the cam (any suggestions?)
- change to CNC ported cathedral 799 heads
below are the specs:
1986 GMC K15 4x4 short-bed pickup
6.0 LQ9 block bored to 6.2
6.2 L92 stock pistons
821 LS3 heads ported by Lloyd Elliot + milled 0.020"
GM MLS 0.051 head Gaskets
CR around 10.7
222/230 .598"/.598" 112 LSA custom camshaft
PSI1511 Springs
L92 6.2 Stock intake manifold
92mm DBC WARR throttle body
1 7/8 long tube headers
3 inch dual exhaust w. H-pipe
SM465 manual gear
3.73 differentials
33" mud tires
thx
TECH Enthusiast
Joined: May 2008
Posts: 644
Likes: 575
From: Carnation, WA
Be aware that changing to Cathedral from LS3 heads drives a lot of extra expense. You'll have to source an intake manifold if you don't already have one from before your LS3 heads went on, and perhaps different injectors. It adds up quick.
9 Second Club
Joined: Feb 2004
Posts: 818
Likes: 215
From: VA
With that tall of tire and missing your low end grunt, you could swap gears in the rears and likely leave your engine alone. Edited (looked up your transmission gearing and see you should be pulling stumps at idle lol) 26mph in 1st @ 6500!
Last edited by lazerlemonta; Oct 7, 2020 at 12:19 PM.
hi
I am considering changing the cam or heads in my truck to improve the performance as it is lazy on low RPM but it loves to rev high. the truck is used in sand dunes and I am using around 93 octane fuel.
what step do you suggest to start with:
- milling the heads and install thinner gaskets to raise the compression
- change the cam (any suggestions?)
- change to CNC ported cathedral 799 heads
below are the specs:
1986 GMC K15 4x4 short-bed pickup
6.0 LQ9 block bored to 6.2
6.2 L92 stock pistons
821 LS3 heads ported by Lloyd Elliot + milled 0.020"
GM MLS 0.051 head Gaskets
CR around 10.7
222/230 .598"/.598" 112 LSA custom camshaft
PSI1511 Springs
L92 6.2 Stock intake manifold
92mm DBC WARR throttle body
1 7/8 long tube headers
3 inch dual exhaust w. H-pipe
SM465 manual gear
3.73 differentials
33" mud tires
thx
I am considering changing the cam or heads in my truck to improve the performance as it is lazy on low RPM but it loves to rev high. the truck is used in sand dunes and I am using around 93 octane fuel.
what step do you suggest to start with:
- milling the heads and install thinner gaskets to raise the compression
- change the cam (any suggestions?)
- change to CNC ported cathedral 799 heads
below are the specs:
1986 GMC K15 4x4 short-bed pickup
6.0 LQ9 block bored to 6.2
6.2 L92 stock pistons
821 LS3 heads ported by Lloyd Elliot + milled 0.020"
GM MLS 0.051 head Gaskets
CR around 10.7
222/230 .598"/.598" 112 LSA custom camshaft
PSI1511 Springs
L92 6.2 Stock intake manifold
92mm DBC WARR throttle body
1 7/8 long tube headers
3 inch dual exhaust w. H-pipe
SM465 manual gear
3.73 differentials
33" mud tires
thx
-Bump the compression to about 11.2-11.3:1. Thinner gasket and cut the head some more. It'll make the whole combo better and torque everywhere.
- More lift, I think the cam is ok, but those heads need more lift to make them effective. 1.8 rockers, probably non-adj Yella Terra's will help. Probably 15-20hp right there.
- 3.73's and 33's is killing the whole combo. I would go straight to 4.30's and maybe 4.56's. No matter what you do motor wise, this will always hold you back, especially if you have less than a 3000rpm stall.
EDIT: Rod mod your intake also. You may even consider a ported L92 Intake, just for the longer runner to help the low/mid range. I would do everything else first and then try that.
Last edited by DualQuadDave; Oct 7, 2020 at 12:55 PM.
LS1Tech Sponsor
Joined: Jan 2008
Posts: 2,235
Likes: 1,526
From: Ohio, Georgia, Nevada, Texas
OP,
Some great advice you're getting from the community.
We like your idea of going with cathedrals for the use of this combo. Rectangle port heads are great for flow but less efficient below peak torque. They're not a good match for trucks used as trucks. As Grabinski said with switching to cathedral there will be added costs. Obviously, those could be offset some by selling the ported LS3 heads.
Compression is your friend here. You could mill the current heads more and get a thinner head gasket to boost compression. Usually, once you start getting around .030" milled or more the intake will start needing to be angle milled as well. Just going with some .040" compressed thickness head gaskets should put you right around 11:1.
We also like the idea of a gear change. If this is just being used in the dunes some 4:30-4:56 gears like DualQuadDave mentioned would help. That would surely make it more responsive for off idle and part throttle response.
The cam specs look pretty good. If you had the ICL or how much advance is ground in that would be helpful to see where the valve events are at.
Depending on your budget and how far you want to take this build you could change up the rotating assembly. More specifically going to a 4" stroker assembly. Something we have in mind for this would be our Pro LS SUM-R58400656 rotating assembly. All forged rotating components with a 6cc dished piston. With a stock head gasket and your milled heads, you should be right around 11:1. Drop to a .040" gasket and bump it up a little more. This would give you that low-end grunt you're looking for as well as improve power and torque across the board.
Some great advice you're getting from the community.
We like your idea of going with cathedrals for the use of this combo. Rectangle port heads are great for flow but less efficient below peak torque. They're not a good match for trucks used as trucks. As Grabinski said with switching to cathedral there will be added costs. Obviously, those could be offset some by selling the ported LS3 heads.
Compression is your friend here. You could mill the current heads more and get a thinner head gasket to boost compression. Usually, once you start getting around .030" milled or more the intake will start needing to be angle milled as well. Just going with some .040" compressed thickness head gaskets should put you right around 11:1.
We also like the idea of a gear change. If this is just being used in the dunes some 4:30-4:56 gears like DualQuadDave mentioned would help. That would surely make it more responsive for off idle and part throttle response.
The cam specs look pretty good. If you had the ICL or how much advance is ground in that would be helpful to see where the valve events are at.
Depending on your budget and how far you want to take this build you could change up the rotating assembly. More specifically going to a 4" stroker assembly. Something we have in mind for this would be our Pro LS SUM-R58400656 rotating assembly. All forged rotating components with a 6cc dished piston. With a stock head gasket and your milled heads, you should be right around 11:1. Drop to a .040" gasket and bump it up a little more. This would give you that low-end grunt you're looking for as well as improve power and torque across the board.
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Big *** rig, wrong gear to tire ratio, and fat port no torque heads till past 5000...
Stock cathedral 799’s, Truck or TBSS intake, stock throttle body. Purdy cheap.
With those tires, 4.56.
Big *** rig, wrong gear to tire ratio, and fat port no torque heads till past 5000...
Stock cathedral 799’s, Truck or TBSS intake, stock throttle body. Purdy cheap.
With those tires, 4.56.
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TECH Addict
Joined: Jul 2013
Posts: 2,189
Likes: 123
From: Portland, Oregon
Some gear would definitely help... I would also go with 4.56 gears, as others have mentioned.
Cam is good, but could use some more lift... some 1.8 rockers will probably be enough to get you there without changing too much else.
IF, and I mean IF, you want to change your heads, I would go with cathedral ports. TBSS intake.
But I would try gears first, then higher ratio rockers, before changing anything else.
Cam is good, but could use some more lift... some 1.8 rockers will probably be enough to get you there without changing too much else.
IF, and I mean IF, you want to change your heads, I would go with cathedral ports. TBSS intake.
But I would try gears first, then higher ratio rockers, before changing anything else.
Thread Starter
Teching In
Joined: Mar 2008
Posts: 5
Likes: 1
thanks a lot for your opinions
I think that I will start by changing the gearing or tires before touching the motor and see how that works
then I might keep the LS3 heads mill them, use thinner 0.040 gasket to gain more compression, install 1.8 rocker arms
in the same time will evaluate going with cathedrals if I can sell the LS3 stuff (heads, trionion rockers, L92 intake)
- 799 heads already available
- CNC porting (around $500 for a local shop but I need to see their flow charts)
- new cam suitable for cathedrals (another $500)
- NNBS or dorman intake, fuel rails( $100 - 360 used or new)
I think that I will start by changing the gearing or tires before touching the motor and see how that works
then I might keep the LS3 heads mill them, use thinner 0.040 gasket to gain more compression, install 1.8 rocker arms
in the same time will evaluate going with cathedrals if I can sell the LS3 stuff (heads, trionion rockers, L92 intake)
- 799 heads already available
- CNC porting (around $500 for a local shop but I need to see their flow charts)
- new cam suitable for cathedrals (another $500)
- NNBS or dorman intake, fuel rails( $100 - 360 used or new)
Those AFR Enforcer heads are cheap because they are not CNC’d, they’re meant to be as cast replacement heads and in no way do they perform like AFRs CNC performance offerings. Great way to go if you don’t already have of 243 heads and don’t want to spend the money for rebuilding heads. RHS is making as cast LS3 heads for replacement heads in the way, no extra big flow, just heads.
Last edited by 64post; Oct 8, 2020 at 10:28 PM.
Be interesting to see just how much those new AFR heads would benefit from some hand porting in the right hands.
Gears will help a ton. 33’s and 3.55 are more suited to a turbo car looking for max 1/4 mile performance. 😊
Gears will help a ton. 33’s and 3.55 are more suited to a turbo car looking for max 1/4 mile performance. 😊
9 Second Club
Joined: Feb 2004
Posts: 818
Likes: 215
From: VA
https://en.wikipedia.org/wiki/Muncie_SM465_transmission
That is a link to his transmission. You put 4.56 in this thing it will be like granny gears. First gear with 3.73 and 33" tire @ 6500 rpm 26 MPH Second 48 MPH and third is 101 MPH. With 4.56 @ 6500 its 21 MPH 39 MPH and 82 MPH
That is a link to his transmission. You put 4.56 in this thing it will be like granny gears. First gear with 3.73 and 33" tire @ 6500 rpm 26 MPH Second 48 MPH and third is 101 MPH. With 4.56 @ 6500 its 21 MPH 39 MPH and 82 MPH
Last edited by lazerlemonta; Oct 8, 2020 at 03:59 PM.
https://en.wikipedia.org/wiki/Muncie_SM465_transmission
That is a link to his transmission. You put 4.56 in this thing it will be like granny gears. First gear with 3.73 and 33" tire @ 6500 rpm 26 MPH Second 48 MPH and third is 101 MPH. With 4.56 @ 6500 its 21 MPH 39 MPH and 82 MPH
That is a link to his transmission. You put 4.56 in this thing it will be like granny gears. First gear with 3.73 and 33" tire @ 6500 rpm 26 MPH Second 48 MPH and third is 101 MPH. With 4.56 @ 6500 its 21 MPH 39 MPH and 82 MPH
TECH Fanatic
Joined: Dec 2005
Posts: 1,414
Likes: 28
hi
I am considering changing the cam or heads in my truck to improve the performance as it is lazy on low RPM but it loves to rev high. the truck is used in sand dunes and I am using around 93 octane fuel.
what step do you suggest to start with:
- milling the heads and install thinner gaskets to raise the compression
- change the cam (any suggestions?)
- change to CNC ported cathedral 799 heads
below are the specs:
1986 GMC K15 4x4 short-bed pickup
6.0 LQ9 block bored to 6.2
6.2 L92 stock pistons
821 LS3 heads ported by Lloyd Elliot + milled 0.020"
GM MLS 0.051 head Gaskets
CR around 10.7
222/230 .598"/.598" 112 LSA custom camshaft
PSI1511 Springs
L92 6.2 Stock intake manifold
92mm DBC WARR throttle body
1 7/8 long tube headers
3 inch dual exhaust w. H-pipe
SM465 manual gear
3.73 differentials
33" mud tires
thx
I am considering changing the cam or heads in my truck to improve the performance as it is lazy on low RPM but it loves to rev high. the truck is used in sand dunes and I am using around 93 octane fuel.
what step do you suggest to start with:
- milling the heads and install thinner gaskets to raise the compression
- change the cam (any suggestions?)
- change to CNC ported cathedral 799 heads
below are the specs:
1986 GMC K15 4x4 short-bed pickup
6.0 LQ9 block bored to 6.2
6.2 L92 stock pistons
821 LS3 heads ported by Lloyd Elliot + milled 0.020"
GM MLS 0.051 head Gaskets
CR around 10.7
222/230 .598"/.598" 112 LSA custom camshaft
PSI1511 Springs
L92 6.2 Stock intake manifold
92mm DBC WARR throttle body
1 7/8 long tube headers
3 inch dual exhaust w. H-pipe
SM465 manual gear
3.73 differentials
33" mud tires
thx
Thanks.