I have a 1999 Gmc s-15 sonoma with a mild engine knock on cyl #3

Haven't rebuilt, just tore down to check valves,guides,pistons,rings,etc.

Pulled plug wire also stethoscope test its Def coming from 3 no rebuilde yet just diagnosis at this poi.

This is a puzzle,i have been doing this a long time.Most noise gets worse in a warm engine. I know a machinest/motor builder, been doing this a long time too.I'll ask this wizzard and get back if can help.Something is expanding and then fits better.