LS6 Heads Standard On 4.8 And 5.3 Engines? 
LS6 Heads Standard On 4.8 And 5.3 Engines?
Interesting.. I knew the older ones didn't. If they are true 243's.. then the newer stuff must be coming with dished Pistons.
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From: Ft. Lauderdale, Fl.
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From: Ft. Lauderdale, Fl.
Wondering why GM makes the same exact LS aluminum heads, but with different casting numbers? Even if they had different springs & valves, etc., whats the logic in manufacturing different casting numbers? Its not a model year identification, is it? I've worked in manufacturing my entire life, and usually there is a reason for this. Usually its due to a design change, be it small or large, or some other reason. But the same exact casting, with different casting numbers doesn't sound logical.
Last edited by LS1GMCTruck; Oct 3, 2008 at 11:29 AM.
Here is a quote from Richard at WCCH
"The 799 casting was mainly used as a pre production head. I'm not sure how many early ZO6's were shipped with them, but I don't think too many because I have only seen them on a very rare ocassion. They are virtually the same as the 243 casting. In fact, I used a pair of 799 heads to test our Stage 2 LS6 program on and the cleanup was complete. Let me know if this helps.
Good luck,
Richard "
GM Mold Numbers As I understand it, the numbers tell what original mold the casting came from.
Supposedly, the 243 mold was done at GM Research, the 799 mold furnished to other vendors. The same vendor may have the 243 and 799 mold.
The numbers are a GM system indicating when the mold was made. If a head develops problems, it helps them track down where the problem started.
There are production vehicles having a 243 head on one bank and a 799 head on the other.
I believe the production 799 heads began to appear in late 2006. There were no serial production (or prototype LS6) engines being made in '06 (yes, there were service/ crate engines). Why would a 2000(?) prototype head be put on serial production '06 engines??
Supposedly, the 243 mold was done at GM Research, the 799 mold furnished to other vendors. The same vendor may have the 243 and 799 mold.
The numbers are a GM system indicating when the mold was made. If a head develops problems, it helps them track down where the problem started.
There are production vehicles having a 243 head on one bank and a 799 head on the other.
I believe the production 799 heads began to appear in late 2006. There were no serial production (or prototype LS6) engines being made in '06 (yes, there were service/ crate engines). Why would a 2000(?) prototype head be put on serial production '06 engines??
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From: Ft. Lauderdale, Fl.
Only Genuine LS6 heads have the hollow stem valves This appears to be one of the common misconceptions about heads having the 243 casting no. -- they are not necessarily LS6 head assemblies. The LS2 heads (243 or 799 casting) have the "heavy" standard LS1 valves. However, they do have the LS6 springs.
Only the true LS6 engine heads have stainless steel (not titanium) hollow stem valves (the exhaust stems are sodium filled). These valves are slightly longer that LS1 valves too.
The LS7 heads do have titanium valves.
New LS2 heads are about half the price of new LS6 heads (check sdparts.com). GM is "really proud" of those hollow stem valves!
Oh, if you have the 799 castings -- the only thing "Corvette" about them is the valve springs/retainers! Still a desirable set of LS1 heads though!
Only the true LS6 engine heads have stainless steel (not titanium) hollow stem valves (the exhaust stems are sodium filled). These valves are slightly longer that LS1 valves too.
The LS7 heads do have titanium valves.
New LS2 heads are about half the price of new LS6 heads (check sdparts.com). GM is "really proud" of those hollow stem valves!
Oh, if you have the 799 castings -- the only thing "Corvette" about them is the valve springs/retainers! Still a desirable set of LS1 heads though!
Not trying to hijack but looks like people here have info...
So this means a 243 and a 799 has the 2.00 intake valve?? even if its on a 5.3?? Ive got a set of 706's with the triangle under the plug, nothing special about them is it?? Im pretty sure they have the 1.89 valve. And dont the later model 5.3 heads have the D-shaped exhaust ports what casting# are those heads, 243s? And does anyone know the chamber size on all these?
So this means a 243 and a 799 has the 2.00 intake valve?? even if its on a 5.3?? Ive got a set of 706's with the triangle under the plug, nothing special about them is it?? Im pretty sure they have the 1.89 valve. And dont the later model 5.3 heads have the D-shaped exhaust ports what casting# are those heads, 243s? And does anyone know the chamber size on all these?
Launching!
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From: Ashland,VA
I have a 06 aluminum 5.3 that im swaping in my camaro. It has flat tops and also has 799 heads. They are 2 in intakes and 1.55 exh. Was reading on the corvette forums about the differences of the 243s and the 799s and the vette guys are pissed. some of the early production 06 vettes have 243s and some have 799s. that got all the vette guys checking their heads and some of them even had a 243 head on one bank and a 799 on the other. A guy from gm said that the difference between the 243s and the 799s is the way they are cast. the ports on the 799 casting are not as smooth as the 243 casting and it is beleived that there is about a 5-7 hp loss with the 799s over the 243s. just thought i would throw that info out there. the vette guys are really pissed about it. they feel like gm screwed them out of 5 hp!!
799 Heads Yes, both heads have identical sized intake and exhaust valves.
A poster on the Corvette forums (Gohard777) had a "in" at GM research.
"Mr. X" (from GM research) assured him that the only differences (other than the casting no.) were production variances. Allegedly, "Mr. X" machined the first set of 243 heads himself at GM research.
Other posters have advised that the 799 casting was used in development of the true Ls6 heads. That is, 799 castings were the prototype Ls6 heads.
I don't know of any dyno tests where the 243 has been proven superior to the 799 casting (or vice versa). You are free to "believe" what you wish!
AIR, at one time it was "believed" the world was flat.
I've had a set of used 799 heads in my hands -- I can see no real difference in the castings. However, my set of 243's is ported and I don't claim to be a cylinder head expert.
A poster on the Corvette forums (Gohard777) had a "in" at GM research.
"Mr. X" (from GM research) assured him that the only differences (other than the casting no.) were production variances. Allegedly, "Mr. X" machined the first set of 243 heads himself at GM research.
Other posters have advised that the 799 casting was used in development of the true Ls6 heads. That is, 799 castings were the prototype Ls6 heads.
I don't know of any dyno tests where the 243 has been proven superior to the 799 casting (or vice versa). You are free to "believe" what you wish!
AIR, at one time it was "believed" the world was flat.
I've had a set of used 799 heads in my hands -- I can see no real difference in the castings. However, my set of 243's is ported and I don't claim to be a cylinder head expert.
Staging Lane
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From: CP Humphreys, South Korea
The motor I bought for my LSX swap is the L33 out of an 05 Silvy, it has the 799 casting heads and Alum. block. So I can't wait to install this beast in my 04 Colorado. When I have the cam done I will have the heads sent out to be ported and polished, a small gain, but a worthy one.