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

[bozzhawg]

I think Bozz is a bit confused....

Disregard Dennis, I completely over looked the name, I just glanced, yalls names are close..... I guess I am getting old....

[bozzhawg]

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

Well they sell it haus, hard and the average kid or joe looking for sexy horsepower will trick off that cash faster than a dude in a room full of butt naked strippers....

[B'klyn9C1]

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.

Dennis,

Thanks for the reply. I knew that if I just exercise some patience you'll come through in the end.

I am sorry I have to ask some dumb layman's questions regarding your suggestions on the LS3/L92 heads.

On point #1, what do you mean by "Stand the valve job up as much as possible..." ? Does this involve some angle milling the head to change the vave stem angle??

On point #2, what is to "Set intake throat @ 91.5% and exh at 90%" ??

I understand the other two points but you got the explain what are "big runout numbers" that the LS3 and LS7 heads are notorious for?

Again from the feedback I have been getting is that single pattern cams are definetly not advised on these heads. One engine builder who is big here in the northeast emailed me that in his experience the larger duration on the exhuast side tended to lead to less reversion and a cleaner(less contamination) and quicker intake charge.

From some quarters I get the definite message that all I need to do to get to my 500 RWHP/500 RWTQ goals is that I don't really have touch these heads at all. Just get a good low miles powertrain let's say a wrecked '07 or newer wrecked Cadillac Escalade with its L92/6L80E combo, deactivate the VVT and the DOD. Choose a cam wisely and that is it without changing the rotating assembly or even opening the valve covers.

That might be true, but feel free to comment on that sentiment. But I feel I can best cover my bets with a 408+ cid stroker. And if i go that route I want to do the best bang buck improvements to the heads since they will be off the shortblock anyway. And not waste money on binch of unnecessary procedures that produce very marginal results at best.

So does pocket porting and bowl blendwork worthwhile on these heads??? Or do the "just leave these damn heads alone" camp have a point??

Colin

[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

Well they sell it haus, hard and the average kid or joe looking for sexy horsepower will trick off that cash faster than a dude in a room full of butt naked strippers....

One time... once it doesn't do what they wanted they aren't coming back

[frankthetank]

I know this is an old thread, but I have a similar combo I am putting together with similar goals in power. Trying to get to 600hp at the flywheel without too much work in the heads or buying aftermarket.

What struck me as interesting when I first read it years ago was airflowdevelopment recommending a 91.5% intake throat...my math says 3.0042 inches at the throat with stem diameter removed...

It seems large based on what pipemax recommends etc....but trust that AFD knows his stuff so I assume that the csa is really in the port at some point upstream?

I am wondering if that is still the consensus or what you guys recommend 9 years later?

[Rowdy Yates]

For 500/500 with a manual trans and a 415 porting is a must! (Makes it that much easier) Unless S/R and 11.5+ compression. A good cam and port work with as much compression as you can get °11.8'ish. 500 rwhp is easy it's the 500 ft-lbs of TQ with the larger port Ls3 heads. Compression & shorter duration cam with ported heads. Bolt on's help....header,ewp,etc. Single pattern cam with ls3 heads is out ..... Frank and the other young man said it. SSR, Bowl/Throat and a good valve job on the intake. Leave the Intake runners as is & Work the exhaust. A Good CNC program runs min. 900
and you'd be done. You don't even need a aftermarket intake. Factory intakes Perfect for 500/500 with a 415 & 6700-6800 peak.

[Rowdy Yates]

Throw in a Low lash S/R cam....with ported Frankenstein Ls3 heads & stock Ls3. Recommended the porter...wink,wink.

https://www.camaro5.com/forums/showthre ... morel+4737

[CGT]

a 91.5% intake throat

Everybody has their own way, application ect. But to me, the fact that GM left the throat small is a good thing, gives you some flexibility there to do what you want to do. How much lift are you running? Automatically just going to 91.5 no matter what the situation doesn't make sense to me.

...my math says 3.0042 inches at the throat with stem diameter removed...

Correct. That's what it would be at 91.5% of the 2.165 valve. By my measurements that would make the throat...maybe the minimum but not quite...the port has a lot of area changes in it.

To keep the throat the minimum, and to get the same amount of taper back you lost after doing that to the throat would require going back through the port and making a port that's already to big for most stuff even bigger. There is a place for that kind of sizing, but at that point I think you would be at an rpm where something besides a stock casting that's weak and thin in the rocker stand and spring pad area would be better.

It seems large based on what pipemax recommends

It is. My thought is why make it worse.

[Orr89rocz]

For 500/500 with a manual trans and a 415 porting is a must! (Makes it that much easier) Unless S/R and 11.5+ compression. A good cam and port work with as much compression as you can get °11.8'ish. 500 rwhp is easy it's the 500 ft-lbs of TQ with the larger port Ls3 heads. Compression & shorter duration cam with ported heads. Bolt on's help....header,ewp,etc. Single pattern cam with ls3 heads is out ..... Frank and the other young man said it. SSR, Bowl/Throat and a good valve job on the intake. Leave the Intake runners as is & Work the exhaust. A Good CNC program runs min. 900
and you'd be done. You don't even need a aftermarket intake. Factory intakes Perfect for 500/500 with a 415 & 6700-6800 peak.

Bone stock heads with fresh valve job and mill and stock ls3 intake made over 500 whp on a friends 416 stroker ls3. Manual trans 9” rear fbody. It was 520’s whp. Torque was close to 500 but not quite there i dont believe. Dont need porting but it would help if you made the mild changes mentioned in this thread

[frankthetank]

I am doing just that, had a nice vj put on. Kept the 45 degree seat.

He did leave the last cut into the throat at what about 89%, I am at the point where enlarging it would be easy.

I was looking for any personal experience with the big throat on a mildly reworked head at 416 ci and about 6800 rpm max.

Leaning towards doing the basic vj blend in and remove bolt and spring bump and that’s about it. Hard to shrink the throat later if I make it too big.

I would agree with CGT from my limited experience, throat is where I think mcsa should be if possible. But heads are unique I guess. In context, the bow tie vortec works well with a big throat on a 2.00 valve. I always thought it was due to valve size...

Lift will be around .650, It seems about the limit with the stock rocker pad. Hydraulic roller mostly due to trying to keep stock rockers etc. ls3 int valve, springs will be whatever is recommended for the cam. Used férrea inco exhausts because you never know...

Thank you guys for the replies, my combo will have a 4l80 with a billet lock up converter, so 600 fwhp is what I would like to get close to.