yes, get a filler gauge and get the right specs for intake/exhaust valve clearances and do work. If your lifters are already very worn that they are flat instead of oval than the valve adjustment wont reduce the noise by much. Check compression, see if it's even through all the cylinders. If it is than the valves are closing well. If it's not than there is a possibility that some valve is not closing all the way, which could be fixed by a valve adjustment.