Would 243 or 799 heads be good for boost? I'm currently runnin stock 862. I've heard 317's are a good boost choice head. Lookin for opions.

Mods

5.3, procharged, 11 psi, 220/220 .581/.581 112 cam

 

That's what I run

 

If you think bout it, the 07+ trucks 4.8/5.3 has 243 heads.
They raise your CR to 9.9? Or 10.0? And flow alot better than the 862s.

Be neat to see a diff on a dyno on the same turbo/boost #.
Just the bump in CR should make a small diff in vacuum.

 

I just didn't want to go over on my cr and possibly blow somethin sky high. Would running a different gasket maybe help keep the cr down a little more?

Denali, how much boost are you running?

 

Actually, they will lower the compression on the OP's truck. The 862's have 61cc chamber's, and the 243's have around 64cc chamber's, or something like that. The boost in compression on the newer 5.3's comes from flat top pistons. Someone correct me if I'm wrong here.

243's need to be milled .028-.030 to get the chamber's down around 61cc's. If you are ok with running milled heads, I would have them shaved and run LS9 gaskets with ARP head studs for boost. You would never have problems lifting a head at high boost. 317's aren't an option unless your looking for an all out race setup. The chambers on those heads are 72cc's or something close, your loss in compression would make the truck run like **** out of boost, and you can't mill them enough to do much about it. However, they would be much more resistant to detonation at high boost numbers so if your looking for track only power then they would work well.

 

alot..... haha

 

and 243s have a larger chamber than 862s/706s.......?

 

correct

 

Wow i was wayyyy off!!

I must be thinking bout the 706s??

 

For some reason, the L33 5.3 achieves a 9.9:1 CR using flat top pistons, and 799(exactly the same as 243) cylinder heads.

This begs the question, are there 2 different size combustion chambers for 243 heads?