L92/L76 Intake Manifold Flow Comparison
Originally Posted by thunder550
I think I answered my own question. Here are the L92 and LS2 truck manifolds together. You can see the difference where the gasket would go.
Richard
On The Tree
Joined: Sep 2007
Posts: 107
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From: Oklahoma
I am still waiting for the Weiand intake coming out this summer. It is for the L92/LS3 heads. It will come in 2 finishes & is out of composite light weight material. They have part numbers for it already & say this summer. I have a TrailBlazer SS LS2 with L92 heads with forged bottom end & now using truck L92 intake. Truck guys will have to change out water pump to clear the TB (use GTO water pump) pointed toward radiator not up like the truck. Driver side accessory bracket & idler pulleys may have to change but pic's show it tilting up more so maybe the water pump only will do it. They are getting over 28 hp over a L76 or truck they say in testing. Cheap also $550.00 range.
LOL
LOL
info on intakes Great information Richard, I appreciate your diligence and effort in this research. Whether or not Weiand, FAST, or whoever comes out with a "performance" intake for the L92's, its obvious that GM raised the bar on the factory styled rectanglular cylinder heads at a fraction of the cost of most aftermarket heads. I will run a ported L76 intake w/ my heads ( which are not installed yet) until I see a better product available.
Richard, I've seen you refer to the L76 manifold as the modern-day single plane manifold and the L92 as the modern day dual-plane. Is that to say that the port velocity in the truck manifold is higher than the car? IE, the truck manifold is the "torquer" manifold and the L76 is the HP manifold? Or that the truck intake is capable of developing more low end torque and the car more high end hp? It could be that I am thinking about it too traditionally???
J. J.
J. J.
Richard, I've seen you refer to the L76 manifold as the modern-day single plane manifold and the L92 as the modern day dual-plane. Is that to say that the port velocity in the truck manifold is higher than the car? IE, the truck manifold is the "torquer" manifold and the L76 is the HP manifold? Or that the truck intake is capable of developing more low end torque and the car more high end hp? It could be that I am thinking about it too traditionally???
J. J.
J. J.
Although I am not an intake scientist, here's a brief overview of our perspective on intake systems.
There's much more that goes on in any single or multi cylinder intake manifold than port velocity. With engine speed, in micro seconds air pulsates back and forth due to the valves opening and closing. Within those events sound waves are generated that travel up (and down) the lenghts of the intake (and exhaust) runners creating a "ram tuning" effect. Manifold runner length then has a contibution to make regarding cylinder filling at differing cycling speeds. The "truck style" L92 intakes have a longer runner than the L76 intakes and thus they are capable of generating greater amounts of cylinder filling at lower engine speeds. Search for a program called "Pipe Max". It will give you many answers to the questions regarding torque production vs rpm.
Thanks for sharing your information.
Richard
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Launching!
Joined: Mar 2011
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From: wi
this thread has been dead for a while and there a re plenty of people running the factory trunck intakes. anybody got any rwhp numbers running a truck intake? l92 or cathedral port.im going to run a lingenfelter gt-11 cam with l92 heads ans the l92 intake.wont rev high but will have lots of area under the curve and be a good street and open road car.
TECH Resident
Joined: Jul 2005
Posts: 861
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From: Midland
this thread has been dead for a while and there a re plenty of people running the factory trunck intakes. anybody got any rwhp numbers running a truck intake? l92 or cathedral port.im going to run a lingenfelter gt-11 cam with l92 heads ans the l92 intake.wont rev high but will have lots of area under the curve and be a good street and open road car.
I have done several test on the flow bench porting intakes and throttle bodies bolted to the heads without anything to expect a dyno gain from. The only way I found to increase the airflow was to cut an intake and epoxy a radius to the port entry. Epoxy in the intake isn't something I would trust over a long period of time so you can't use it plus you have to cut apart an intake to get the back runners and it just isn't worth it. So for a while I have sat on the bench not really pushing or recommending intake work because it is usually a "wash" on gaining anything. Now with another car to modify, it seems I revist the same delema of trying to get more from the same drum I have beat to death already. Well, I found it! Hear is the flow results:
Livernois heads with 5 axis valve job and bowl blend with a VMS ported intake bolted flowing thru a ported throttle body:
Lift CFM
.300- 201.0
.400- 248.1
.500- 278.8
.600- 294.1
.700- 302.7
Lift CFM w/ same heads ported and modified intake
.300- 212.3 +12.3
.400- 262.6 +14.5
.500- 294.1 +15.3
.600- 313.5 +19.4
.700- 324.5 +21.8
Lower lift gains are from porting/valve work to the Livernois intake port on the heads. Higher lift gains are mostly the intake .500-.700" The intake has a radius bar installed on either side at the runner entrance. Just thought I would pass this on since I haven't seen anyone post "ported" intake flow numbers. I would guess the main reason is porting the runners doesn't show any gains on the flow bench worth talking about. What the gains are worth on a dyno is anyones guess, but potential is there.
Livernois heads with 5 axis valve job and bowl blend with a VMS ported intake bolted flowing thru a ported throttle body:
Lift CFM
.300- 201.0
.400- 248.1
.500- 278.8
.600- 294.1
.700- 302.7
Lift CFM w/ same heads ported and modified intake
.300- 212.3 +12.3
.400- 262.6 +14.5
.500- 294.1 +15.3
.600- 313.5 +19.4
.700- 324.5 +21.8
Lower lift gains are from porting/valve work to the Livernois intake port on the heads. Higher lift gains are mostly the intake .500-.700" The intake has a radius bar installed on either side at the runner entrance. Just thought I would pass this on since I haven't seen anyone post "ported" intake flow numbers. I would guess the main reason is porting the runners doesn't show any gains on the flow bench worth talking about. What the gains are worth on a dyno is anyones guess, but potential is there.
Standard LS3 style castings. Standard L76 intake. Base test was a Livernois LS3 head with their valve-job and bowl blend and a VMS ported L76 intake bolted on. Next test was with a radius bar installed in the same intake and some cleanup work valve back-cut on the same heads. Same head and intake using the same port, just "before" and "after" results.
Last edited by G8-4-speed; May 6, 2012 at 07:44 PM.
