Car is going in the shop next week and I am trying to make the best decision. Car is getting L92/L76, LTs, Cam, Tune etc. Have a couple of questions.

Has anyone put ported L92's on a LS2 and what were the results? The shop that is doing it has expressed concerns about ported L92's saying that the ports may be too big and mismatched to the motor causing poor port velocity, poor cylinder filling, and a loss of low rpm power. I am guessing if this is true it will be a better option to stay with "untouched" L92's.

Hoping LG or someone with some hands on experience will chime in with some real world results but ANY input will help!! I have read so much over the last couple of weeks my head hurts LOL.

Heads haven't actually been ordered yet but need to be ordered soon so they will be here in time.

Thanks

 

if the heads were ported correctly the port volume shouldnt be too much higher then stock. and dont get caught up in this port velocity stuff. because stock the port volume is quite large and GM is running these on 5000+ trucks with 6.0's and 6.2' motors, so i think on your car you will just fine.

 

Every L92 headed build I've seen so far makes great low/mid RWT - including mine. Slap them on and let us know.

 

Be careful with the camshaft selection.

As for the port velocity argument there is some merrit to it. Its best to think of velocity in terms of 2 distinctly differing types of localized and Genral. Localized velcotiys like on the short side turn can be very high wheras the general velocitys can be very low across the entire port in a small 200cc catherdral.

If you pay careful attention to what GM has done with this port you will notice that they have tried to reduce localized velocitys and increase over all genral velocity. Now you ask yourself why would someone do this.

2 reasons come to mind.

One is fuel/air seperation from high local velocitys in specific areas of the port cuasing to much tumble and swirl as you enter the chamber and making the fuel smash into the cylinder wall cuasing ring wash and could potentially cuase the dreaded piston wearing that creates piston slap. " ford 4.6 2v motors from 96-99 had a similar issue"

Two is that if you work to hard on haviing areas with highly specific verticeis you will have a head that has uneven flow distrobution.

Also it allows you to select camshaft timing events that are more conducive to making a nice broad specific output without having to resort to camshafts that create infficient combustion.

You could also factor in the ability to Detune the engine in the sense that the current ls1 ls6 style manifolding and ports generate a very narrow and specifically tunned RPM range for Optimal TQ output. Now with the larger cross section and less specific tunning the use of a camphaser allows them to implement a much broader operating range by detunning the engine so that its natural harmonics resonant tunning FQ is less specific and focused.

So thats just my take on it enjoy.

 

One thing to remember is that the engine doesn't know the difference between the cylinder head and the intake manifold - it's all one long runner with a valve at the end. And the runner design defined by the L76, similar to the other plastic intakes, produces a strong tuning resonance in the mid range that largely overwhelms the effect of intake port cross section on the torque curve. Otherwise, this motor would be a real dog in a truck. Also, the exhaust port is small to begin with for engines of this power level.

As long as the porting is done by experienced L92 porters, and doesn't remove too much material, the effect on torque will be minimal. On the other hand, given the high RPM limitations of the L76, you may not see a large gain on a 6.0L motor from porting, since you can't spin it high enough to take full advantage of the increased flow. Either way, though, you should make good power.

 

while runner length does play a huge role in the specific tunning of the intake "l92/ls1/ls6 all have roughly 16inchs of runner length from seat to entrance" increasing the cross section generally moves that operating range and specific tunning further up the RPM band for a given displacement all things being equal.

an l92 intake on a 347 360 402 408 427 454 etc would be power peaks as follow
6600,6450,6300,6250,6100,5950

and that is becuase when you increase the amplitude of the filling cycle you drive down the operable FQ.

Enjoy.

 

Most ports are still pretty close to stock runner sizes. We ship our complete cnc ported heads configured for LS2 engines all the time. My personal car made 440rwhp through a automatic & a little 228 camshaft!

Jason

 

Good points in this and the previous post. Increasing the overall cross section definitely does raise the frequency of the intake tuning point, although the intake port represents a fairly small percentage of the total runner cross section. If someone were to figure out how to port the L76 intake, particularly toward the runner entrance to create more runner taper, that would be a different story.

And the tuning frequency does go down with increase in displacement, as everyone building big inch L92/L76 combos has been discovering. The L92 definitely needs an aftermarket intake design to fully reach its potential on the bigger inch/higher RPM combos.

 

Thanks for the replies everyone. A lot of what you are saying is over my head.

Looking for something real simple like a dyno sheet showing RWHP and RWTQ numbers to compare to one I have that shows unported L92 heads.

Once again a stock bottom end LS2 engine.

 

Sorry for guiding the thread off track. To summarize the points in the posts thus far:

- The torque curve in an L92/L76 combo is mostly determined by the L76 intake manifold, and you won't lose much if anything in low end torque if the head porting is appropriately conservative.

- Jason's results of 440 RWHP with an A4 and 228 cam say that ported L92s can offer great results in absolute terms on an LS2.

I don't know of any back-to-back comparisons of ported vs. stock L92s on a 6.0L engine - all of the test results I've seen were on 400+ inch motors. Maybe TSP has some tests they've done.

And just my opinion - porting LSx heads in general seems to be a tricky business, and I wouldn't do any porting at all unless you use one of the most experienced shops (say, TSP or Greg Good or similar).

 

Thanks-I am looking at the ones from Livernois Motorsports.

 

Can anyone else help out on this topic?

 

My advice is mild cam with untouched heads.

 

LSICURIOUS- I see you have a 402 peaking at 6,300. I spoke with LG motorsports(lewis)today about a custom cam for my 402/l92/l76 set up and he told me it will peak around 6,600ish. He said cam selection/set up is a big deal. Will it peak at 6,600ish....I DON'T KNOW when i get it tuned we'll see. Also,I will kinda be testing this cam because it's not in anyones car yet. I hope it works out.

 

Thats just data I have seen posted up.

 

I bought a pair of heads from Greg Good Cylinder Heads in Houston that he hand ported.... he changed the 2.165 intake valve to a 2.125 valve and put a 1.60 exhaust valve in vs the stock 1.59 valve.

here are the flow numbers:

Stock it flowed 317/218 @ .600

After porting:
238@ .300 intake
297@ .400 intake
360@ .600 intake

257@ .600 exhaust


BTW, his bench is in par with the bench at Sam Racing's flow bench. Now floating numbers here. ( I dont think Greg would do another set of L92 heads, unless the fellas was really serious about making power and breaking some records. :wink: :wink:

My advice is to get them ported.... most of the sponsors like Livernois and LG etc have CNC versions that are around the same price and flow in the same ballpark. Only thing I didnt like is the fact that the valve is larger then the seat and the flow over the valve along with shrouding on a 4.030 or smaller bore.

Good luck! BTW, most porters wont touch the runners.... at 260 they are already too big, I believe the heads I had done are around 262 or so.... .he didnt mess with the runner size much.

also... if you can afford the extra 1200 or so for ported heads go ahead and do it! more flow the better. your problems with stock L92's is valves, valve jobs, exhaust flow, short turn radius, and chamber size. Stock intake flows 330cfm IIRC.

 

Here's a long post that goes through a direct comparison of ported vs unported L92 heads on a 403. There's also a lot of other good info that was shared.

https://ls1tech.com/forums/generation-iv-internal-engine/662314-l92-dynojet-numbers-plus-plan-b-c-d-e-f.html