I'm looking into getting a set of stock 5.3 heads to clean the casting and polish the ports, and maybe do a valve job and mill a little. How much gains am I looking at?

 

If you do a proper competition valve job,you'll see a useful increase in performance.Whatever you do don't try to hog out the ports you can do more harm than good.

 

I was planning to just clean up the casting flag left (if there is any) and polish the crap out of them. Then I got to thinking it would probably be a good idea to do a valve job also, and maybe mill the down just a little.

 

I did a 5 angle valve job on mine, larger intake 2.00, unshrouding and .050 off thats it and of course 918's and ferrea 6000 series valves. Along with the cam this thing freakin screams the stock heads flow alot better than you think, if I were to get a port job I would only go stage 1. Keeping the intake runners tight and just removing material from the bowl helps keep velocity up which is what creates torque. To give you an idea I ran the numbers in my sig NA 5.3 in a 5400 lb z71
thats why chevy small block is king!!

 

I wasn't going to port at all. Just clean up any casting left, and polish real good. I guess a valve job would be a good idea too.

 

Matt, my buddy still has them heads off of his 5.3. Blended valve guides, cleaned up casting and polished, 3-angle v-job, milled .020. Good for about 3 tenths.

 

What does a competition valve job involve? 5-angle grind and bigger valves? Anything else? Thanks!

 

I have heard that is better to go with a 3 angle job for street apps when I get my heads from WCCH they will have a 3angle job cause thats what richard recommended. But of course this going to be on the 6L too not sure if that would change anything.

 

A good competition valve job needs to be performed by an experienced professional and would include undercutting and radiusing the valves along with a 5 angle seat and hand lapping.A really good competition valve job should be worth about 20 to 25hp

 

he is absolutely right I paid 800 for the work and materials I had done to my heads and its well worth it, thats why no other ext cab NA z71 are even close to my times. Just because someone you call says this or that doesnt mean its right they want to sell you a product