I am fixing to buy a set of assembled patriot 6.0 heads for my 5.3. I have a procharger p1sc and the rest of the motor is stock. I know this will lower the compression which is what I want in order to run more boost. Does anyone know how low the compression is with these heads. I hope it will drop it to about 8.5. Any help will be much appreciated.

 

That is about right for the CR drop, maybe even a few tenths lower.
There is a sticky somewhere on this site that has all the info you could need on the GenIII heads and interchange, else for sure over on LS1Tech.com ( look in the Internal Engine areas ).

 

stock i belive is 9.5 with i believe is a 62cc head. a 317 is a 72cc head so it should drop it ot about what you stated

 

6.0 heads on a 5.3 is going to cause valve shrouding due to the larger valves in the 6.0 heads....I'm not sure it'll be a BAD problem but you will end up with lower max flow potential

 

I concur with Yellow. BTW stock heads on my Av were 61.15 cc @9.5. The new Stage 2 Patriots have a 63 cc with 2.02/1.57 Ferreas...They net me 500rwhp with the Vortech. My heads flow benched 295 @ .600. Shrouding was a consideration when I went to these heads. Truck is a beast....

 

http://www.rbracing-rsr.com/compstaticcalc.html

Can't remember where I found this...

 

Your going to need to run a 6.0l head gasket with the 6.0l head. There's a difference in gasket bore volume that you shouldn't forget to account for. It should account for almost 2cc of volume.

Good luck,

Richard

 

What size are the valves in the stock 5.3 heads. The valves in the patriot stage 2 heads are 2.02 int and 1.57 exh.

 

Stock valve sizes for the 4.8l and 5.3l heads are 1.890"/1.550".

Richard

 

What if I get my 5.3 block bored to a 3.905 bore. With the bore being bigger that should help out with the valve shrouding problem.