b005td

iTrader: (9)

not sure i should post it on the gen iii or gen iv, anyways

i got a set of ported 5.3 heads they are suppose to flow like the AFR 205, and I also have a ported LS6 intake manifold.
question is if i use them on a 99 6.0 iron block, is that a upgrade or downgrade from the stock lq4 heads ??
thanks

sroach20

iTrader: (31)

big downgrade, that would be like trying to breathe through one of those small coffee straws. you could go with ls6 heads to raise your compression and still flow.

B4CU

iTrader: (18)

I know a guy that just milled some 317 heads since they are the same as 243 heads but just with a bigger combustion chamber. As long as you don't use a huge cam the valve clearance should be good. On a 99 LQ4 I think they are iron heads, so I would say the 5.3 head would be better since they are lighter, flow like AFR 205 heads, and bump the compression. Even with not that great of flow the compression bump would be worth it...that is what I think anyway.

b005td

iTrader: (9)

... so is it really gonna gain or lose hp ?

the_merv

iTrader: (88)

If they are Iron, then yea, it's goin to be an upgrade. Look for a set of LS2/LS6 Heads, and get an LS2 intake on it with a 90mm Throttle Body..

ufsnola

iTrader: (13)

I'm not an expert by any means, but the ported 5.3 heads are going to bump the compression of the LQ4 by about a point. The LS6 intake will help in high rpms. As long as the ported 5.3 heads flow well I don't see any negative side to running that setup... I say if you have the parts already use them.