I have an 02 Chevy Tahoe with the 5.3 motor. I will check the head stamp tomorrow.

 

243 on my '05.

I suspect that this is much ado about nothing.

I can't post the link but this comes from one of those popular auction sites

"If you have been watching my listings over the past month you have noticed that I am quickly becoming "the" source for clean 6.0L parts such as heads blocks and cranks, please check my previous listings and keep track of what I have coming up soon. Coming in soon are more 6.0L parts as well as other Gen III engines. Let me know what your looking for.

You are bidding on a core set of GM Gen III aluminum heads. Casting number 799 (same as 243), small chamber, 1761 Miles. A105 and A125 casting, 2005 model, excellent condition! Please check with your dealer to be sure this is the exact one for your application. May fit other applications, my description is only a guide and I cannot guarantee it is 100% correct, just what I found. Sold as-is! "

 

Good find DSOM. I also searched some more and found this info from a truck website, this is the post......
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Well, I researched the answer to my own question. I'll post here so if anyone else needs the info it'll be here to search for.

The 799 heads are in fact an LS6 casting. They list part no. 12564825 for the 01-04 LS6 engines and the L33. "The L33 takes its cylinder heads from the LS6. Originally developed for the Z06 Corvette, these heads improve airflow in and out of the engine. With their pent-roof combustions chambers and new flat top pistons (the pistons in other Gen III Vortec 5300s have a slight sump in the piston deck), the L33’s compression ratio increases from 9.5:1 to 9.9:1. This increase improves the engine’s volumetric efficiency yet still allows it to achieve full power with regular grade gasoline." They have a D shaped exhuast opening. The heads have a 65cc combustion chamber and a 210cc intake runner.
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And taking the PN from the above post and putting it in the gmperformanceparts website, it comes up with this description

Cylinder Head - Cnc Mach Showroom Stock Version Of 2002 LS6 Head


CNC-ported aluminum racing head
2. 00" Hollow stem intake, and 1. 55" sodium filled exhaust valves
. 570" max valve lift
250 cc CNC'd "Cathedral port" intake ports
85 cc CNC'd D-shaped exhaust ports
61.

 

a few pictures below. apparently they are ls6 pre-production heads also.

pictures courtesy of Andrew on LS1Tech

 

799 Here

Build Date Oct 06

So what are ya'll saying? That the 799 heads are just fine?

 

Well, I've got a build date of 10-13-06. Friday the 13th, I'll have to check tomorrow!!

 

Your Vette does indeed have LS6 cylinder heads.

See above. Much ado about nothing.

 

see if we can get a group of 799 down to the dyno and see where the # falls.

 

Question now is, where the heck did GM find pre-production LS6 heads 2-3 years after the production 243's had already been out, and why stick them in a limited # of 2007 Corvettes??

If they flow the same I'm gonna tout my car as an ultra rare factory 799 vette.......easily worth more then the cookie cutter LS2 w/243 heads

 

Ahhhhh Yeaaa!

 

 

Mine are 243. 2007 with a build date of 10/18/06.

Wayne

 

BTW here is my stock dyno sheet. base run compared with after installing a Halltech stinger intake. My car has the 799 heads.

 

Relax guys, GM is just trying to use up all the old parts that'll fit a LS2 before closing down the Canadian factory that builds this discontinued engine. When the new Wixon built LS3 engines start going in the '08s in July, there won't be any use for these old parts.

 

799 heads here build date 10/06

 

As a long time Vette owner I can tell you that over the years there GM has made virtually hundreds of slightly different heads for the previous small blocks. Some were obviously better than others. I have seen two heads with the same casting number but different valve sizes. Casting numbers are just that. The raw casting before machining. Part numbers are the real identifier of your heads as a finished part.

 

Coming back to the original question why does this car have low dyno numbers with the mods that have been done? Assuming the 799 heads are the same as the 243 there must be another reason! Sometimes it's hard to remember your objective was to drain the swamp when you're up to azz in gators...

 

Correct. And tjwong is a tuner of note and may be able to respond as well after he checks his client's #s. (see his earlier post on this thread #41)) However, as stated just above, it MAY not be that the two heads ARE exactly alike in performance, even tho they have the same part numbers. Simple interchangeability does not mean equal.

 

799 Heads on 12-06 build date. Now what?

 

Exactly.... and there in is the root of the problem! My guess is you'll never get GM to address the issue. "IF" the 799 heads actually cause a slight decrease in hp who's going to know the difference except someone that dynos. Even at that would be next to impossible to prove without spending a lot of money. Not worth the expense! Maybe instead we can get some new badges made.... 243 or 799 heads?