2003 LQ4, T76 turbo,
do I need to up grade the valves?
such as stainless steel one piece, stock size.
am upgrading to Z06 cam and Valve springs.
along with head bolts/ studs,
currently 8psi, looking to increase to 12psi.

also best head gasket for this set up?

 

Stock are fine for 12psi

1 piece stainless if you have the extra cash would be a nice upgrade.. Ls9 head gaskets work great for boost.. 4.030" bore cometics in whatever thickness you need will work too

 

It seems you are on a budget so 317 heads all the way! 243 or 862 if you are running E85.

 

We tested several aftermarket against stock valves for tensile strength. The stock valves tested 50% higher than the best aftermarket valves in the bunch, so I feel they're very durable.

 

Really? At what temperature?

 

Room temperature.

I think the best aftermarket valves failed at 120,000 psi and the stock GM valves failed at 180,000 psi.

Ductility wasn't measured, and would be important if you start bouncing the valves or hitting them with the pistons...

I would think a harder valve with higher tensile strength would be more prone to fracture if it were hit. So there are pros and cons to tensile strength versus ductility.

Since 1998 I haven't had a GM valve fail.

 

Thanks for the info !!
I was concerned about the 2 piece valves!
besides the LS9 and cometics, any other brands of gaskets durable enough?
(felpro, etc)
I am assuming multi layer gaskets.

 

Hmmm good to know!

 

You can use regular 4.030 gm Mls gaskets too

The ls9's are nice since they're cheaper than cometics but have 7 layers and are designed for FI