No picture but if you look at your picture, you can see where the valve smashed down on the piston, but there was no mark in the actual valve pocket. that shelf keeps the deeper valve pocket form being used. they are hitting the 90 degree shelf first.
If you grind of that shelf so it is the same angle as the valve pocket, you just gained, (as i keep saying:D) a boatload more clearance. we are talking about thousands of an inch here and that 90 degree shelf has.......I don't know .020 to get it to the stock valve relief????
Latter i will look up my old valve to piston clearance and share them with you, to show the difference it made.
Have to find my notes first.
Earlier i said to us a cut of wheel to do the job. Have changed my mind. us a die grinder and a alu bit or a sand paper roll on a die grinder. make sure you clean up any sharp edges. you could even replace the die grinder for a drill for that matter.