Mark Johnson

iTrader: (1)

Hey guys,
for the longest time as moany of you know I've been set on punching out my 5.3 to 5.7. Lately I got a wild hair to go 6.0 thinking that I was that far already, and anyways- torque is what I'm after, up at 7,000ft no less. But I've also reviewed valve placement, that is the distance of the intake and exhaust valves from each other and that they're not too close to the cylinder wall. I've deducted that the heads on the run of the mill 6.0's are less than ideally positioned as the heads were originally intended to the 4.8/ 5.3 bore and also why the L92 heas are all the rage for 6.0 blocks.
So I guess I'm back to punching out my 5.3, just probably not all the way to 5.7. So the big question; what is the optimal bore size with the valve placement in the 5.3 heads? Is there more to be had here? Should I just throw everything to the wind and go the 6.0 route and 5.3 heads..............

Mark Johnson

iTrader: (1)

Valve placement, anyone..................

Coban

iTrader: (14)

How did you come up with that? As far as I know, 317s were never intended for 4.8/5.3 blocks.

The reason why people like the L92 heads is: (from CarCraft)
Valve Lift Intake L92 Exhaust L92
0.100......72............63
0.200......148..........126
0.300......212..........162
0.400......264..........189
0.500......302..........205
0.600......322..........214
0.700......316..........221

High flow for cheap. And the combustion chambers are smaller than the 317

Here's the stock 317 port: (WCCH)
Lift......Int...........Exh
.100" ..64.8........53.3
.200"..142.1.......111.6
.300"..204.3.......146.8
.400"..233.5.......164.9
.500"..250.0.......174.2
.550"..251.2.......181.2
.600"..253.0.......184.4

budhayes3

iTrader: (19)

Correct, 317's are 6.0 specific heads...I was under the impression that they were designed from and are very similar to the LS6 heads...

Mark Johnson

iTrader: (1)

317's? Really, hmm- didn't know that. So now I'm teetering between hogging out my 5.3 and the 6.0. I'd love to stick with the 5.3 heads................

Coban

iTrader: (14)

Use the 6.0 shortblock with the 5.3 heads. Close to 11:1 compression but the 5.3 heads don't flow very well, relatively speaking.... Should be pretty torquey though.

Zippy did a build like that for a Tahoe. He massaged the 5.3 heads a little though.

Mark Johnson

iTrader: (1)

Thanks for enlightening me on the heads, guys. L-92 heads are waaaay outta my league. Look's like 6.0 and 5.3 heads are in order. I went ahead and perused zippy's build a little and learned a bit, too. Torque is what I'm after, so if the engine signs off at 5 or 5,500rpm that's fine..............