looking to see how much power gains to expect when i swop my stock ls1 heads for 5.3 truck heads.
long tubes - full exhuast - tune - and cam are the major parts changed.
cam specs: 234 238
gross lift .598 .605
lobe seperation 113

 

other than 5.3L heads...what are they...stock, ported, milled?

if they are stock, you should see 400-420rwhp easy

if they are ported you could easily see 440-450rwhp

 

car made 415 whp with current settup.
from what ive been told the 5.3 heads just have a little work all around by a local machine shop.

 

Hard to tell what a little work all around means exactly, but you might see 20 - 30 HP from the heads depending on how good a job they did.