badazz81z28

iTrader: (6)

They didnt have the yellow spring either. There is some controvery on this one. Some people say they did, but yeah, if no yellow springs from the factory highly doubtful the valves are light weight.

ZeeOSix

It is true that the 2001 LS6 did not have the hollow valves. Good reference article here. Look near the end of the article for the valve info.

http://www.netmotive.net/articles/hib/02ls6/page2.htm

Country1982...

I'm doing a build mild build just complete stock rebuild with stage 2 cam it happens to have stock 243 heads but it's a 2008 dod motor everything I read says they stopped in 2005

G Atsma

243 and 799 heads were made until the end of Gen IV truck engine manufacture. Whatever you read saying otherwise is BS.

02*C5

iTrader: (1)

These heads when ported and polishesed at the time back in the early 2000s only after market heads flowed better. They also came with hollow intake valves and sodium filled exhaust valves very light weight. You could easily rev these to 7500 rpms with the right springs you'd have 0 issues.

I had a set done AI and they where flowing 310 cfms at a .650 lift. Now AI has a 226 runner program that gets them flowing at .650 lift over 320 cfms. Same as a set of GenX tricflow heads. Also they have a 64.5 chambers so by de ault increasing your compression ratio.

really great heads and hard to beat for the money. You look at TF or AFR or other after market head hell Tony Mamo heads are going to set u back 3K easily. Those are some of the best flowing heads. For the money you won't find a better flowing head.

G Atsma

243 and 799 heads were made until the end of Gen IV truck engine manufacture. Whatever you read saying otherwise is BS.
You might be thinking of the particular 243 heads that came on the LS6 5.7L engine. They had the hollow valves and were only made thru the 2005 model year. 243's with solid valves were made for more than 10 years after that, including your truck.

99 Black Bird T/A

iTrader: (4)

GM stopped making the LS6 engine (243 heads) for production cars with the 2005 or 2006 model year, I forget now. The 2005 or 2006 Cadillac CTSV was the last platform using LS6, I believe. However, the 243 & 799 heads were used many years afterwards in trucks until ~2014 when Gen IV engine production wrapped for new vehicles. 243 & 799 are basically same etc.

Country1982...

why are they considered the most sought after factory heads lol I'm tempted to swap heads now

G Atsma

You already have 243 heads, as you mentioned. The hollow valves were for the high performance Corvette engines to keep the valves cooler. The heads you have are plenty good enough for what you do with them. No need to swap anything.

Country1982...

no I have 2 other 5.3 engines 1 of wich is fully built I think 283 heads on both one was built by a machine shop with eagle bottom end he called it a mother thumper cam it's a stage 3 with double value springs I should put the 343 heads there I haven't talked to the old guy to see if he stroked it or not but I know him he may have so it may be a 363 or bigger stroked ls

G Atsma

283?? 343?? no such animal.... On a mostly stock 5.3 the best heads ARE the 706 that are on it, due to the smaller 61cc chambers to keep compression up, in turn due to the 8cc dished pistons.
If you would like your posts to be readable, try using punctuation and sentences. You know, periods, commas, capital letters.... like you learned in 2nd or 3rd grade...

wannafbody

iTrader: (2)

The 706 heads have slightly smaller chambers. The thing that makes the 243 different is the lower floor of the port and the improved short turn radius. The 853 and 241 heads have practically no short turn radius.

99 Black Bird T/A

iTrader: (4)

BandDirector Blk98ZM6

iTrader: (21)

...just to throw this out there, I put a crate 2004 LS6 longblock straight from GMPP in my '98 Z28 back in '04, which of course includes the 243 heads w/sodium filled valves. Motor has never been opened up, I have all the usual bolt ons, and I put down 400.1 RWHP...

Also, the Cadillac CTS-V from that era also had an LS6 rated at 400 HP (vs 405 HP for the C5 LS6) and the reason the Caddy was rated 5 hp less was because it did NOT have the sodium filled valves...at least that's what I seem to remember from back then...

G Atsma

A lot of that is corporate politics. Nothing should equal or outclass the almighty Vette. Plus the Vette might have a bit better intake or exhaust system

99 Black Bird T/A

iTrader: (4)

Fantastic post! Makes my day to read information like that 😊

gagliano7

I always liked the LS6 engine. I had a 05 gto with the LS2 and headers, catback and a tune put down 370 hp. I also remember the C5 LS6 was faster than the C6 LS2 in the 1/4 even thou there HP numbers were pretty identical.

BandDirector Blk98ZM6

iTrader: (21)

…even I was torn at the time…LS6 5.7 405 HP vs LS2 6.0 400HP. Some friends of course said “no replacement for displacement”, but in the end I went LS6 for a few reasons. 1) LS6 was literally a straight replacement/plug-n-play for my stock LS1. Sensors were all in the same spot, and was literally just a matter of swapping my LS1 sensors over to the LS6. The only thing minor I had to do was reroute the PCV valves since they were slightly different than the LS1. 2) Longblock prices were about the same, so the extra 5 HP rating swayed me to the LS6. 3) The “cool” factor. Just sounded cooler to have GM’s top performance engine at the time (C5 Z06 motor) in a Camaro over the LS2 which was the new C6 “standard” engine 🤫

BandDirector Blk98ZM6

iTrader: (21)

It’s a slightly long read, but here’s the page I created back then with all the info to do the swap. On an LS6 intake, it originally put down 377.9 RWHP. I eventually added an underdrive crank pulley, and the Fast 92mm intake w/Nick Williams 92mm TB, and it was those 2 additions that got me to 400.1 RWHP.


http://banddirector.cz28.com/custom2.html

pdxmotorhead

My l33 has 799's I think the 243/799 heads were just one of those random moments when the manufacturer got it right..

Even a blind squirrel finds that nut once in a while...