I have a 2005 silver with the 4.8, and it is getting heads off of a 6.0 that were milled, a cheat v3 cam and some ltd with a an x pipe and cherrybombs. I'm going to be getting it tuned some time next week after it gets put back together. Any ideas on what kind of HP tq increase I will see. There is also a spectre cold air intake. Thanks

 

Around 80rwhp..

 

I think you'll lose some power swapping to those 317 heads. Dropping compression too much, even though they will flow a little better.

 

I agree with Scott, 317s on a 4.8/5.3 are no good IMO. 243s flow just the same but with smaller chamber sizes, so compression drop wouldnt be as much if putting on a 4.8/5.3..

 

-50hp... 317s have a combustion chamber of ~71cc. 862s have a combustion chamber of ~61cc... So even if you mill the crap out of them, i don't think you will be down the combustion chamber size of the 862s.... So your CR will drop, the 4.8 has enough issues, dropping the compression is not going to help...

 

Thank you for the responses, today my buddy called me and said he has a 06- 5.3 engine for sale. It's in great shape. What would you guys do with the same parts.

 

Sell all of it and buy a 6L and a cam and call it good..

 

My 4.8 dynoed 280 with a v3 cam and other basic boltons. So with heads probly in the neighborhood of 305 give or take depending on ur compression with those heads

 

Not only are you talking about BIGGER combustion chambers which will drop compression, power etc.. Theres also the valve shrouding issue as the 317 heads were meant for a 4"+ bore...