So I'm porting and polishing some heads for a build I'm doing and I'm going to be upgrading the valves but the question is should I get oversize valves and bite the bullet with extra machine work cost or go standard size? How much flow gain have people seen with OS valves? Thanks

 

We need 2 no what heads U got & what block is being used Think about it in this way.. you could leave them stock but, Y.You ported the heads 2 gain flow Y would you turn around and defeat yourself. A engine is only as good as the heads.

 

Many VERY GOOD professional porters reuse stock valves.
What on earth makes you think you need to "upgrade" or that you are good enough at reshaping the port to make a larger valve worthwhile?

IMO larger valves are not the magic bullet some guys are going to tell you they are, but even if they were I would say you don't know enough about port work to make them work.

Not anything personal just that I think it takes a real skilled professional to make that kind of improvement to a head. The rest of us can dabble and make some improvement.

 

853 heads ls1 aluminum block have mahle -4cc pistons, Im not doing a lot of work to the intake side. just cleaning up casting slag shaping the guide ramp. the exhaust I've matched gaskets and shaped the ramp and polished it out to a low RA (that's how much/deep the grain is) also polished the combustion chamber.

and the reason I'm getting new valves/ upgrade valve is I'm replacing ones that got bent or broke. I could aways use the stock ones out of my heads that are on the car now but wanted to have everything ready to go on the car before I tare it down
To keep down on the flak about match the gasket and doing work to the short side of the exhaust port I have a ultrasonic tester at work for checking material thickness and will be checking them in near future

 

I'd really like to see factual data like this ported head flowed xx w/ stock valve and xxx w/OS valve rather than opinions

 

TEA and Advanced Induction both offer those heads fully CNC'd with stock valves.

If the stock valves were any sort of problem they wouldn't waste their time using them.

 

I should prolly do some more research on what company's are offering in their heads but are u saying they use stock size or actual stock valve in those head u mentioned

 

Stock valves.

Betting you can get a few replacements on forum easily if you search the classifieds.

 

As previously stated, there has been plenty of success had with the stock valves.

 

TEA will use your stock valves in the Stage 1 port job and upgrade to Ferrea or turned-down LS3s in the Stage 2. Stage 2 provides more power, but it's not tons more. Maybe 7-10HP more.