At what point would you step up to ferrea hollow stem valves
This is just my opinion, so take it for what it costs.
In a performance build anytime you can save weight on moving parts it’s a plus. With valves it equals less spring, which means less stress on rocker arms, lighter push rods. All of which equates to less load on the cam. Light parts rev easier than heavy parts. I like light weight pistons, rods, thin ring packs, anything that moves in the car. It all adds up.
It would be interesting to see dyno results on a stock type rebuild on a 340 compared to one with light weight parts.