I have a 09 crew cab 4x4 sierra with a 5.3 that burns oil badly so I'm upgrading. My truck has the 6l80 and 342 gears. i just bought a ly6 out of a o8 van. The ly6 has the l92 style heads on it my truck came with the cathdrel style heads. So ill need a new intake. Here is my question i have a set of 243 off a 04 cts v would these be a better choice for a heaver crew cab with higher compression or keep the l92 heads? Anyone have a idea what the comp ratio would be on a 6.0 with 243's with stock head gaskets? please help!

plans are:
LY6 6.0
delete vvt
ls9 cam and ls9 valve springs(i can get the cam for $100 brand new)
211/230 562/558 lift 122.5 lsa
arp rod bolts/head bolts
1 3/4 arh long tubes catted Y
stock cat back
dyno tune

i tow a 7000lb boat so i need torque thats the goal. the 5.3 is a joke

 

due to the eyebrows in a ly6 piston , i think you should stick l92 heads . i know the intake valves have differet centers but not sure if this can cause any interference .... unless you planned on building the bottom end

 

Anyone know this for sure if ill have clearance problems? if so how much should i mill the l92 heads to reach a 10.5:1 compression from 9.65:1 it has now?

 

You won't have any clearance issues with the 243s and cam specs your looking at. Your 5.3 has flat top pistons and the same heads so why would a 6.0 have any less clearance?

 

Any idea what the comp ratio would be with the 243's?

 

Hard to say without knowing how many cc's the valve reliefs are. Should be in the 10s though.

 

the 243's should be in the 10.5 11.0 with a flat top and reliefs
if you have the pistons with a slight dish alot lower
stay with the .051" gaskets

 

keep stock l92s they flow really well

 

I decided to stick with the l92 heads all the info I found on people using the ls9 cam na had the l92 heads.

 

Anyone know how much I can mill the heads and still run 87 octane?