Quik

iTrader: (7)

they put 243s on 5.3s from factory. a 243 only flows 250 i think

bluecajun5.3

iTrader: (31)

that head for a larger bore also has 2.00" valves that you plan on using and they also flow more (in cast form) than the stock 5.3's.

tdrumm

iTrader: (18)

LS6 have 3.905 bore, but the valve spacing is the same as a 5.3 head. The larger valve diameter (2.00") combined with the smaller 3.78" bore is what causes the shrouding effect. Same thing would happen when you put a 2.00" valve in a 5.3 head. Milling a head also can negativly affect flow slightly by placing the valve closer to the cylinder.

Quik

iTrader: (7)

but the heads came on 5.3s from factory so it isnt as bad as you think

99/5.3w/hips

iTrader: (8)

yeah but dont the L33 5.3 have flat top pistons so the head wasnt milled to up compression they just went with a flat/domed piston instead? That would be why there is no direct hit on the flow because the valve distance hasnt moved like Tdrumm is getting at.

Quik

iTrader: (7)

not sure at all. I know the LS4 and the 5.3 truck motor runs them and those are the HO motors i beleive

doublenot

iTrader: (12)

I think you can get some dart heads for fairly cheap now. You might check on a set of those.

TXsilverado

iTrader: (19)

patriot performance sells a nice combo..

cnc'd 243 heads with chamber sizes to your liking with prc duel springs and titanium retainers for 1090.

tdrumm

iTrader: (18)

Are you sure that they are 243s? Patriot used to market a "LS6 style" head that was a 317 head that they had weled up the chamber to get the volume down. Also, 2.00" is the max intake valve I'd run on a 5.3, and I'd be willing to bet that those heads have 2.02s and use larger port volumes to get their flow numbers, which could affect low speed torque.

TXsilverado

iTrader: (19)

they use 243 castings now. they just havent updated the website. its under new products on their current website.