As far as I know it's so that the head of the valve can be made from a more resistant material and is then welded to the stem. High revs cause vibrations and strain due to the speed they are moving, so they separate at this weld.
Supertech valves are high grade stainless steel for the intake and inconel for exhaust.
Thanks for that.
I have never considered that valves were ever machined from anything other than a single billet.
But before becoming involved with F4R`s, I had not encountered pressed lobe cams either.
Is the reason for constructing a welded valve purely cost?
If you have a 22mm valve with an 8mm stem, you will need to start with a 23mm piece of billet the total length of the valve, but if welded, two pieces of billet of vastly different O/D dimensions?
Looking at JB21`s singe valve failure, the stem is clearly visable in the valve guide.
Have you any feedback on Sinus valves v Supertech?