my 1986 4 cylinder 4x4 ranger is making a tapping noise. it sounds like its coming from the head. what engines are compatible? i found a 1988 mustang 4 cylinder engine for $80 and a 1989 mustang engine/auto tranny for $100.

i've found a few turbocoupe heads for $50.

what is a common cause of tapping? i'm hoping its not a rod bearing or wrist pin. i haven't pulled the valve cover off yet.

any ideas?