OK guys I have a 5.3 03 rcsb silverado and I just bought a set of 02 LS1 heads with comp duals. I want to actually bump my compression up. I need to know how much I need to mill off these things. Then I also need to know how much lift I can have on my camshaft. Shorter pushrods? if so what size? Say I wanted to mill the heads .030. Then what would the compression be? Please keep on the subject I know about how it wont make any power blah blah blah so please guys just recommendations on above mentioned setup.

 

I Would Go .050 Then Get Some Spacers For Under The Rocker Arm Bar.i Am Running 5.3 Heads On My 6.0 And I Shaved The .030 With A 571/578 Lift With 216/220 Dur. On A 114 Center.i Have Amazing Bottom End,with This Set Up.
If I Remember Right The 5.7 Heads R 65 R 68 Cc A 5.3 Head Is 60 Ccand A 6.0 Is 70 R 72 Cc.
Hope This Helps

 

i dont know on the compression. but you need the shorter pushrods when you mill .030. i think it would make it 10+:1.

 

For starters, check out this thread on LS1Tech. https://ls1tech.com/forums/showthread.php?t=111207
It has lots of the info for CR vs CC/volume, etc.
You probably know the truck 862 heads have a 62cc head volume compared to the 241 car heads with 68cc. To actually raise the compression on your truck over the 9.4:1 you are gonna need to shave a ton off the 241 heads. Once you start shaving you will get into other issues like poor valve train geometry, shorter pushrods, etc. Thinner head gaskets will help but not enough.
The other issue that comes into play is called "valve shielding". This is caused by the smaller bore size ( 3.78" to car 3.898" ) creating turbulence around the valve next to the cylinder wall and impacting flow significantly.
You could source some 243 Vette heads ( 64cc head volume ) but would still run into the shielding problems.
Not sure if this helps or hurts. Try the thread info for more...

 

on the compression Id just use a calculator, I think your gonna end up milling alot to get the compression where you want it.
I leave all that to a proffesional find a good machinist and tell him whats going on then tell him to make it happen

on the valve shrouding have you machinist unshroud the chambers it wont take much and its worked well for me, I have the same size valves you have on my 5.3 while your in there get some competition valves and do a valve job.

buy a pushrod length checker

aftermarket cams have smaller base circles and though your taking material off the heads they will help make up for it, geometry is a bitch I found out the hard way do it right the first time. buy the length checker its only 15 bucks

 

A lot of good info in here, I am still going to at least call a real shop on this like west coast cylinder head to see what he has to say. Thanks to all that responded.