98hardtopZ

iTrader: (7)

I just bought a used camaro a few weeks ago and I know the guy was full of **** when he said it had 04 GTO motor installed because the EGR was still there. It ran good and with the intentions I have I bought it anyways. Well today I'm tearing the motor apart to swap a cam in and I noticed the heads are 706 casting. Isn't that from the 5.3l trucks? The last stud holding the coil pack rail on was missing on both sides so someone has been here before, and there are a few loose bolts on the exhaust manifold as well. Any way to check vin on the block to see if it's original?

cookseyb

5.3 heads, prone to cracking, smaller valves than other LS heads, but smaller chambers and flow well.

cookseyb

They were used on 4.8's also, Get some 862;s and have the bigger valves installed.

98hardtopZ

iTrader: (7)

I think if I'm swapping heads I'm going 243 LS6. I'm just wondering where tf these came from and if the block is original.

98hardtopZ

iTrader: (7)

Since they're 5.3 heads does that mean my compression ratio has changed? I hope my cam package is still good.

Darth_V8r

iTrader: (4)

I've seen guys use 706 heads to raise compression. Supposedly they flow like 853 heads.

Do the 243 heads

G Atsma

If you like the 243 heads look also for 799 heads. Same casting, different application (late 5.3 truck engines). Should be easy to find nowadays.

99 Black Bird T/A

iTrader: (4)

Back in the early LS1 days, the 706 head was the best bang for the buck.

When 706's are ported correctly with new larger 2.00 or 2.02 intake valves, 1.6 exhaust valves and good valve job, good springs, they are almost as good as ported LS6/243/799 cylinder heads. The 5.3/4.8 706 head was the go to choice before 243/799 castings became more available.

Any chance to check with prior owner of the engine and find out the history of the heads? You might get lucky and have a good set of ported 706 heads.

A correctly built and ported 706 will give any ported 241 a run for the money. The 706 is easier to get higher compression out of unless the 241 has the chambers welded up and is then CNC'd.

I had a set of TEA Stage 2 706 heads on my 99 TA for the last ~15 years and 128,000 + miles.

gagliano7

Your compression with the 5.3 heads should have bumped you up to 10.6 as long as your short block is stock. No LS1's came with 706 heads from the factory.

Darth_V8r

iTrader: (4)

Should be easy to verify if the heads were CNC'd or not. Look for the tooling marks on the intake runners on the heads after removing the intake manifold.

Chris Stavropoulos

Apparently it's only the Castech 706 heads that crack. The 61cc chamber bumps compression to 11.1:1. The heads also make quite a bit more torque below 5000 rpm than other heads, and Richard Holdener has shown they make the same HP. It's the best stock head to put on an LS1.

stockA4

I have castech 706 heads on my ls3 pistoned lq4 grocery getter and I can tell you that they are the best for torque and low rpm snap on the street, especially when paired with a relatively small camshaft, I think they would do great on a lower rpm street 5.7 however I would still go with the 243 heads on a 5.7 that sees any dragstrip duties