I'm am gettng ready to buy heads to port this winter. I am curious, do 4.8L and 5.3L heads have different compression ratio's than my 5.7L? If so what would they yield on my 5.7? which would be better?
Any answers are appreciated! Thanks! <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

 

TTT!

 

4.8/5.3 heads on an LS1 will give you a CR of very close to 11:1. You will want larger valves installed as those heads have a 1.89" intake valve stock.

 

Cool! That answers my question and brings up another one. Can you put a 2.02 intake valve into those heads without having to put in a new valve seat?

 

Yes, I think 2.02 is as large as you can go without redoing the seat.

 

Your 5.7 chambers are 67cc, the stock 4.8/5.3 chamber is 58cc, once we CNC the chamber it opens it up to 63cc which is around 10.8:1, I believe the 58cc would yeild 11.3:1, I'm not sure, haven't done the math. The chamber and valve job is very important on that head and we can do both for $200. The 4.8/5.3 chamber is 3.8" wide and the 5.7 is 3.9" wide so the chamber shrouds the valve alot. Hope this helps.

 

That helps alot. I may be getting ahold of you soon for more info on heads.
Thanks