warm the engine to normal operating temperature.
verify idle between 750-900 RPM
disconect the vacuum hose on the distributor.
hook the timing light (inductive goes on the #1 plug wire) ( inline goes inline the #1 plug wire) and red cip to + battery terminal, and black to chassis ground.
pull the trigger on the timing gun aiming it at the crankshaft pulley. atop of the pulley is a series of numbers. the mark in the crank pulley must line up with the "5" on the number tab.
if it is off, use a 12mm wrench to loosen the bolt that holds the distributor in place.
by turning the distributor and monitoring the mark, it will move one way or another.
move it so it lines up with the 5. tighten the 12mm bolt down. verify again it hasnt moved.
remove timing light hook ups.
connect vacuum hose to distributor.
if the mark on the pulley is hard to see, use a dab of paint to highlight it.
it is a mark made with the end of a chiesel, so dont confuse it with a scratch.