# Debate over heads



## Poncho Dan (Jun 30, 2009)

If you all remember, I'm an LS2 guy, and already have the 243/cath-port heads. There are a lot of people that say to move up to L92 heads for better flow numbers, even P/P L92's. I have read in a few places that it is possible to go TOO BIG with intake port size, and it can affect turbulence once the charge enters the cylinder.

Basically, my plan is to some day pick up a FAST 102mm intake manifold with a 102mm Nick Williams TB. I do plan on doing heads and cam at the same time, and if money allows, the intake manifold & TB too while I'm in there. FAST now makes 102mm intake manifolds for cathedral port heads after being strictly for L92/LS3 & LS7 heads.

So my question is: Is it worth dropping the coin on ported L92 heads, or saving that money to have my existing 243's worked? I don't see much talk about how well 243 heads come out after being ported and polished, and some of the websites show flow numbers very similar to or better than bone stock L92's. Is there any advantage/disadvantage to the cathedral port vs. rectangular port?

I am your basic back yard mechanic. I understand most engine functions until you start talking about intake charge velocity, combustion velocity, and some cam stuff.


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## Poncho Dan (Jun 30, 2009)

I probably should have put this in the engine discussion, huh? :lol:


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## dustyminpin (Jun 19, 2006)

My Texas Speed cnc ported LS3 heads with optional hollow stem valves and titanium retainers, FAST 102 mm LSXR intake manifold, 228/232 .595 lift 114+2 LSA cam (way bigger then stock, but not stupid huge), 46 lbs. injectors, and TCI Breakaway torque converter, along with the K&N CAI, Grannatelli MAF, Kooks SS LTs, and Borla catback that I already had, just put down 455 hp and 415 lbs. ft. torque at the wheels last Wednesday. I've had my car back for 7 days now and am still getting used to the power. The cnc ported heads flowed 349 CFM by the way, that's ridiculous cartoon, oh my God how is that possible numbers. Hope that clears things up for you.


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## dustyminpin (Jun 19, 2006)

By the way, the only thing that differentiates the L92 head from the LS3 head, is that the LS3 has lighter/stronger/better valves. If you pay the extra coin and upgrade the valves or go the extra step and have them hollow stem, then it's not an L92 anymore, it's an LS3. I wanted the sodium filled ones like in the Z06 but Texas Speed doesn't offer them, or maybe they are for the LS7 head only and don't fit in the LS3, not sure on that one.


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## hookemdevils22 (Mar 27, 2010)

LS2 Goats w/ L92s. See post 7 for numbers - dudes are making stupid power with stock heads and intakes (even L76's). The LS3 intake manifold does require an LS3 MAP sensor (GM PN 88988583 and an adapter (via katech i think, or it's easy to do yourself) to work with your harness.

also, talk to patrick g (@ ls1tech) for a cam. he's the man when it comes to that stuff.


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## 87GN06GTO07IRL (Aug 10, 2009)

The l92's are remarkable even in stock form. They're dirt cheap compared to other options. Once you sell the 243's you'll be paying peanuts for them. Great upgrade over 243's


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## Poncho Dan (Jun 30, 2009)

I don't like the idea of being forced to use a 4.060 bore head gasket on a 4.000 bore. Sounds like a great place for carbon to collect and create hot spots.


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## GM4life (Mar 18, 2007)

Poncho Dan said:


> If you all remember, I'm an LS2 guy, and already have the 243/cath-port heads. There are a lot of people that say to move up to L92 heads for better flow numbers, even P/P L92's. I have read in a few places that it is possible to go TOO BIG with intake port size, and it can affect turbulence once the charge enters the cylinder.
> 
> Basically, my plan is to some day pick up a FAST 102mm intake manifold with a 102mm Nick Williams TB. I do plan on doing heads and cam at the same time, and if money allows, the intake manifold & TB too while I'm in there. FAST now makes 102mm intake manifolds for cathedral port heads after being strictly for L92/LS3 & LS7 heads.
> 
> ...


You pretty much got it. Large port volume have slower velocity what sacrafices torque. Smaller port volume have faster velocity, in filling the cylinder down low. Its how quickly you can fill the cylinder with air at slower speeds. But on the other hand port volume what makes power on the top end. Smaller ports sacrafice top end but that also has to do with engine displacement. I wouldn't put 243's on a 6.2, 7.0 or 7.4L engine. The same applies to headers. I remember this because when GM had oval, round and rectangular ports on BBC's. I don't think you'll notice too much on the 6.0 engine .2 cu smaller, and if you have a decent cam that matches the engine combo. I found ported 243 heads with LS6 intake flow 280 @ .550". That will vary with who ports it


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## Poncho Dan (Jun 30, 2009)

GM4life said:


> You pretty much got it. Large port volume have slower velocity what sacrafices torque. Smaller port volume have faster velocity, in filling the cylinder down low. Its how quickly you can fill the cylinder with air at slower speeds. But on the other hand port volume what makes power on the top end. Smaller ports sacrafice top end but that also has to do with engine displacement. I wouldn't put 243's on a 6.2, 7.0 or 7.4L engine. The same applies to headers. I remember this because when GM had oval, round and rectangular ports on BBC's. I don't think you'll notice too much on the 6.0 engine .2 cu smaller, and if you have a decent cam that matches the engine combo. I found ported 243 heads with LS6 intake flow 280 @ .550". That will vary with who ports it


This is where I'm wondering if the cathedral shape/profile actually _improves_ charge turbulence over a plane-Jane port... I know GM wouldn't have done it just for grins and engineering busywork. Cam profile has a lot to do with charge velocity and volume as well - which is a whole other can of worms I need to figure out yet.

I did notice some people have put ported 5.3 heads on their LS1's.


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## jpalamar (Jul 22, 2008)

Poncho Dan said:


> I did notice some people have put ported 5.3 heads on their LS1's.


I think the 5.3s up your compression on the LS1s.


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## GM4life (Mar 18, 2007)

Poncho Dan said:


> This is where I'm wondering if the cathedral shape/profile actually _improves_ charge turbulence over a plane-Jane port... I know GM wouldn't have done it just for grins and engineering busywork. Cam profile has a lot to do with charge velocity and volume as well - which is a whole other can of worms I need to figure out yet.
> 
> I did notice some people have put ported 5.3 heads on their LS1's.


Cams have little to do with velocity and volume of the head. The cam manipulates the charge and volume that enters the cylinder. If anything the intake manifold has more to do velocity and volume of the head. That's just my .02. 5.3 heads have the same ports as LS1 heads, but smaller combustion chambers. When ported they offer better flow over the LS1 head and higher compression equals a bump in power cheaply.

I think GM kicked the aftermarket in the nutts with L92 head.


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