Is there a lot of value in porting LS3/L92 heads??

[B'klyn9C1]

I thinking of building a LS3/L92 stroker motor to 415 CID to go into a 1995 Caprice. The car is a Daily Driver and want to produce 500 RWHP/500 RWTQ with good street manners.

I was thinking that since the engine will be apart during the rebuilding process. Is it worth porting (either hand or CNC) the LS3/L92 heads or just do a valve and clean up job???

I ask this in light of the fact that Vengeance Racing is able to produce 520 RWHP/500 RWTQ on a 415 CID L92 on Pontiac GTO through a M6 with unported L92 heads and an unported L76 intake through careful cam selection and tuning.

I am particularly interested if porting the exhaust side will enable me to run a single pattern cam so I can get the most area under the curve and great low and midrange power??

[T-flow]

Yes, the throat, SSR, and small port changes will help. What intake?


T-flow

[CGT]

T-flow, I too would be interested in any information you may have on these heads. I have a new LS3 camaro and am contemplating whether or not its worth it to pull the heads to work on them. I have heard the throat is small, but would like to know more about what you've done or seen and how changes you made affected the efficiency of the cylinder head.

Thanks
Chad

[swatson454]

Lingenfelter offers CNC porting of various LSx heads that we used for a twin-turbo build a couple of summers ago. It might be worth a conversation with Kevin over there. 260 724-2552


Shawn

[Stan Weiss]

As many of you know I have a Cylinder Heads Flow Data web page - http://users.erols.com/srweiss/tablehdc.htm

A month or so ago I updated it with some new numbers that I received from Darin Morgan.

I think this maybe be of interest to some here.

These are flow tables from a stock GM LS3 cylinder head that I did for my own 2010 Camaro. the head are worth 30hp just bolting them on. After I installed a cam, raised the compression to 11.5:1 and ported the intake the car ran 11.42 at 118.8mph

Darin

Stan

[OldSStroker]

I thinking of building a LS3/L92 stroker motor to 415 CID to go into a 1995 Caprice. The car is a Daily Driver and want to produce 500 RWHP/500 RWTQ with good street manners.

I was thinking that since the engine will be apart during the rebuilding process. Is it worth porting (either hand or CNC) the LS3/L92 heads or just do a valve and clean up job???

I ask this in light of the fact that Vengeance Racing is able to produce 520 RWHP/500 RWTQ on a 415 CID L92 on Pontiac GTO through a M6 with unported L92 heads and an unported L76 intake through careful cam selection and tuning.

I am particularly interested if porting the exhaust side will enable me to run a single pattern cam so I can get the most area under the curve and great low and midrange power??

Your performance goals are worthwhile, but your analysis of what a single pattern cam will do is not, IMO.

It may be better to not "port" the L92 heads but rather just assure that the valve job is round, concentric and seals the valves.

Actually, the stock engine does a good job making low and midrange power (torque). Raising that level whicle keeping the torque curve about the same shape should satisfy your goals without breaking the bank. Not every cam guy does this well, unfortunately.



Jon

[allblowdup]

The reason for the big split in duration and big l/c is because of the big valve used and the factory long runner intake. When you go to a carbed intake then the cam events get a little closer to what we are used to seeing. I would get the heads ported and with a good cam you can hit those goals easily. Guerra motorsports has done alot of cam stuff with the ls3 engine. I am sure they as well as camking and others on hear can really help select a cam as it is seems to be extra critcal with these engines.

[PWMAX]

A valve job, bowl and short turn work, and ex porting, they pick up 28hp. Nothing done to the chambers. The throat is small for the valve size from the factory. You could even put in a smaller intake valve, that fits the throat, and do the same work, and it might work better. If you are re-using the factory valves, I would do a revised valve job, open the throats to 89%, do the bowls, short turns, get rid of the big rocker bolt boss in the runner, and port the ex. It will pick up.

Frank

[B'klyn9C1]

Yes, the throat, SSR, and small port changes will help. What intake?


T-flow

I was thinking a running a a ported L76(or LS3) intake from LS2 Portworks. I heard that the intake is the chokepoint on these heads. I don't feel like spending the heavy coin on FAST LSX intake.

[B'klyn9C1]

I thinking of building a LS3/L92 stroker motor to 415 CID to go into a 1995 Caprice. The car is a Daily Driver and want to produce 500 RWHP/500 RWTQ with good street manners.

I was thinking that since the engine will be apart during the rebuilding process. Is it worth porting (either hand or CNC) the LS3/L92 heads or just do a valve and clean up job???

I ask this in light of the fact that Vengeance Racing is able to produce 520 RWHP/500 RWTQ on a 415 CID L92 on Pontiac GTO through a M6 with unported L92 heads and an unported L76 intake through careful cam selection and tuning.

I am particularly interested if porting the exhaust side will enable me to run a single pattern cam so I can get the most area under the curve and great low and midrange power??

Your performance goals are worthwhile, but your analysis of what a single pattern cam will do is not, IMO.

It may be better to not "port" the L92 heads but rather just assure that the valve job is round, concentric and seals the valves.

Actually, the stock engine does a good job making low and midrange power (torque). Raising that level whicle keeping the torque curve about the same shape should satisfy your goals without breaking the bank. Not every cam guy does this well, unfortunately.



Jon

Well Jon,

In the feedback that I have been getting is if there is anything I've heard about these heads once and thousand times it is that these things breath way differently than cathedral port heads. Also that a single pattern cam is not the way to go. But a dual pattern cam with a slight split with a few degrees favoring the exhaust side maybe okay. Some advocating bigger than let's say ten degrees and this will still keep good street manners. They say that is just the way these heads are.

Funny thing I emailed this question to one of the country's legendary head porting gurus and he told me that considering the my car is a DD and even taking into account my performance goals he said to leave the heads alone.

Wow!! Are these heads that good stock???!!

[T-flow]

If you don't want RPM and such. Maybe just a cam change would help. Doing the heads and cam IMO would grant you the biggest gain! But it would effect overall power throughout the whole curve, Peak, and to gain full advantage of the new air flow. A cam would help !

T-flow

[airflowdevelop]

Colin,
I would have a hard time leaving the heads completely alone... Though it will take very minimal work to achieve your goals. I don't see a way around some split on the exh duration thought it doesn't need to be as crazy as some make it. For what you are doing I would recommend the following.

1. Stand the valve job up as much as possible... This will dampen the overlap making the car drive a little nicer.

2. Set intake throat @ 91.5% and exh at 90% (why not remove a little pumping loss while we are in there)..

3. Check and machine valves as necessary to restore concentricity (the ls3/7's are notorious for big runout numbers).

4. Mill to desired chamber volume.

once you go any further then this for your application... your return on investment goes down the drain.

BTW, I did receive your email...figured best to kill 2 birds w/ one stone.

Best of luck and hope you found the combo that fits your needs.

[bozzhawg]

Guerra motorsports has done alot of cam stuff with the ls3 engine..

Dennis I agree with you prob 98% of the time but this reccomendation I don't... They have gone on record to say that the most they have ever gotten out of over 300+ cams spec'd or dyno tested on a LS3/L92 6.0-6.2 headed engine was 450-460rwhp..... That tells me they are not something right or specing/guessing wrong... We know they push AFR hard over there....lol..... Remember how they tried to hide your article......lol that was not done on accident..... They were pissed......that the truth cam out.... and when the truth cam out the marketing machines flooded the dyno section with brand X dynos, go over there and see now, they are gone....

Bozz

[SStrokerAce]

Bozz,

Just because someone tries a bunch of cams doesn't mean they know what they are doing... and just to go off of dyno numbers for a specific output of a setup on another dyno is pretty foolish... the fact that people think that chassis dynos from place to place are going to be anywhere repeatable is laughable considering they are now the biggest marketing tools in use today.

Bret

[airflowdevelop]

I think Bozz is a bit confused....