Intake valves rarely burn, it's the hot
exhaust gasses that burn an unadjusted
valve

You could have prevented this
A fairly common practice is the regrind the
intakes and replace the exhausts, and I would
pop for the extra few $$ to put in Stainless
Exhausts, I have seen them for about $12
ea. which is much better than the $20 I paid
for mine.
Best to fix that head before you ruin the valve
seat, the seat is cooled by the head, so it burns
much slower, but it will get grooved if you keep
going.
Wild