From: https://www.hotrod.com/articles/measuring-setting-valve-piston-clearance-advanced-guide/
This article advocates checking valve piston clearance by using light checking springs and a dial indicator, rather than clay or play dough. They say that “The tightest clearance between valves and pistons does not occur at maximum valve lift, but instead at two places during the piston travel. The intake valve is closest to the piston in the vicinity of 10 degrees after top dead center (ATDC), while the exhaust valve rides closest roughly 10 degrees before top dead center (BTDC). “ I’m sure positions outside that are worth checking, too.
This article advocates checking valve piston clearance by using light checking springs and a dial indicator, rather than clay or play dough. They say that “The tightest clearance between valves and pistons does not occur at maximum valve lift, but instead at two places during the piston travel. The intake valve is closest to the piston in the vicinity of 10 degrees after top dead center (ATDC), while the exhaust valve rides closest roughly 10 degrees before top dead center (BTDC). “ I’m sure positions outside that are worth checking, too.