How do you adjust timing on an 88 astro?

First you need to have a timing light, once you have attained one (if you didn't already have one) you have to hook up the alligator clips on the respective battery terminals and the inductive lead on the #1 cylinder spark plug wire. Next you need to loosen (not remove) the distributor hold down clamp bolt. With engine running, you need to watch the timing marks on the vibration dampener attached to the crankshaft pulley and adjust (turn) the distributor clockwise or counter clockwise until the appropriate mark (see the emissions sticker by hood latch for desired timing setting) lines up with the pointer on front of motor, being VERY careful not to let and wires for timing light or any part of you get too close to cooling fan! When the lines match, tighten clamp and you should be fine. It may take two people (one to watch the marks and one to turn the distributor) to adjust.