What are the stock valve size on 5.3 (706) heads?
BTW what our the bigger valves you can put on these heads?

 

Stock are 1.89 intake and 1.55 exhaust.

I went with 1.95 intake and 1.57 exhaust. You can go up to 2.00 on the intake, but you start to run into valve shrouding.

 

I'll be running 2.08 and 1.60 in 5.3 heads, but on a larger bore 6.0L. I need to sell some more things on Ebay to pay for the machine shop to rough in the bowls so that I can start my port work, then have the valve job done... so many projects, so little time...

 

These heads are probably gonna go on a iron block 5.3L stroked to 5.7L or in a stroked 6.0 forged 370 with all the goodies capable of holding a 250 or 300 shot of n2o

 

FYI, your stroke will remain the same going from 5.3 to 5.7L as it's just the bore that's punched out to 99mm (standard bore for LS1). I've been thinking about picking up a 4.8 truck with a 5 speed and doing the 99mm bore with forged rotating assembly too!!!

 

In that case, take advantage of the bigger bore and step up to 2.02 or so intake.

 

Yes that bored out to 5.7 not stroked my bad. My bro is not sure if he is getting the 5.7 or the 370, which one should be better, both engines are forged btw?

 

What about exhaust?

 

I would think 1.57 would be sufficient.