boosted_LS

whats the difference between the two?

Fbodyjunkie06

iTrader: (10)

Exactly the same. Both have 317 heads with 220cc chambers and 2.00 intake and 1.5 exhaust.

The CR difference comes from the flat top pistons in the LQ9

boosted_LS

isnt there some of the lq4 heads that are cast iron instead of aluminum?

A.R. Shale Targa

iTrader: (2)

99 and some early 2000 6.0 liter truck engines had the cast iron heads...don't
know the #; doesn't matter. I don't think the LQ9 (345hp) was available until
2001 Escalade, then 2003 Silverado SS. Dished pistons = LQ4; Flattops = LQ9

boosted_LS

ok thanks guys

what comp ratio will that net me with a 5.3l short block? im planning on building a turbo motor

A.R. Shale Targa

iTrader: (2)

You'ld have to do some cc calculations since @ 71cc the 317 heads will
drop the comp quite a bit on the 5.3. I'd just guess from 9.5 to around 8:1
The other thing to consider is the 317 castings have a chamber designed for
a 4" bore engine and the 5.3 is 3.78"...even though you're goin' turbo it's
still not ideal for valve unshrouding if theres a ledge where the chamber
is larger than the bore. Maybe just run a thicker cometic head gasket w/5.3
heads to lower it to 9 to 1

boosted_LS

thats what i was worried about. what would be a better head to switch to? or would it work to bore the 5.3 out to 5.7 specs and use ls1 style pistons?

boosted_LS

while at the woodward cruise today i had the opportunity to pick the brain of one of the gmpd engineers and i asked him about the lq9 heads on a 5.3 block and he said they would be fine but it required a special head gasket. any thoughts on this?

boosted_LS

looking into it some more would a ls1/ls6 head be a better combo than the lq4/lq9 heads?

boosted_LS

anything?