frankmarroquin

iTrader: (31)

Ok well my question is how can I get my 317 heads to flow more like the LS6 heads... I have heard bout "milled down" but I am not sure what to do cause of my mods.

Engine Mods:
2005 LQ9 6.0
317 Heads
GM Hot Cam
LS6 Springs
Monster MotorSports Tune
LS6 Intake
LongTube Headers

And once off I will probably get them ported. How much do they need to get milled

magic

iTrader: (4)

the 317 heads are very similar to the LS6 243 heads....only difference is the combustion chamber volume between the two. The 317s have a larger volume = lower compression ratio.

When people say to mill down the 317s, they just mean to have a machine shop shave/mill down the surface of the heads(combustion chamber) to decrease the volume of the combustion chamber = bump up compression ratio...

But if your engine is an LQ9, it already has a better compression ratio (because of the flat top pistons, the LQ4 had a slight dish piston which resulted in a 9.4:1 compression ratio for the LQ4, versus about 10:1 for the LQ9), so I wouldnt fuss with the heads...

Schwanke Engines

iTrader: (1)

We have been milling them down to about 68cc. Some heads vary in the amount removed to get there, so we just always shoot for the volume.

frankmarroquin

iTrader: (31)

So it wouldn't make much of a difference? Or would it just give me to much compression?

NemeSS

iTrader: (127)

317 basically have the same intake and exhaust port as 243 heads
but with 71cc chamber, 243 has 65cc chamber
a good amount to mill is .035 = 10.15:1 scr from 9.4:11 stock
.040= 10.25:1
i personally do not like to remove anymore than .040 max on any ls head
my bad, this would be assuming the engine is a LQ4
I thought yours was LQ4,

for LQ9 stock SCR is 10:1
amount to mill equals
.021=10.5:1
.031= 10.75:1
.040= 11.0:1