"Timing" refers to the time when the engine's distributor sends an electrical current to the engine's number one spark plug wire. If the engine is not timed correctly, performance and fuel millage will suffer. Checking and adjusting the timing on Pontiac's 350-cubic-inch engine is fairly simple due to the engine's simple design, and the entire process takes only a few minutes.
The timing cannot be checked or adjusted without identifying the engine's number one spark plug wire, and without locating and marking the timing marks. The number one spark plug wire on a Pontiac 350 is the spark plug wire closest to the front of the engine on the driver's side. Locate and mark the correct timing points on the timing pointer and on the harmonic balancer. The timing pointer is a small metal piece located on the front of the engine, just to the left of the harmonic balancer. The timing pointer has several lines stamped into it, along with the numbers "0," "6" and "12." The correct timing point is 9 degrees, so the line between the "6" and the "12" should be marked with either a piece of chalk or day-glo paint. The line stamped into the edge of the harmonic balancer must also be marked.
Pull the single rubber vacuum line off of the distributor's side, then use either the tip of a pencil or a golf tee to plug the opening in the hose so that the engine's idle speed will not be affected when the timing is checked.
The timing light has three wires exiting its handle. The end of one wire has a red alligator clip; another wire has a black alligator clip; the third wire has a clamp that looks like a box. Connect the red alligator clip to the positive battery terminal and the black alligator clip to the negative battery terminal. Open the clamp on the third wire and attach it to the number one spark plug wire. Start the engine and point the timing light at the timing pointer and harmonic balancer. Pull the light's trigger. The light will flash each time current travels through the number one spark plug wire. The mark on the harmonic balancer should line up with the mark on the timing pointer. If the two lines do not line up, the timing is not correct.
Turn the engine off, then loosen the single bolt which holds the distributor to the intake manifold with a wrench. The bolt is located underneath the distributor, where the distributor enters the intake manifold. Turn the engine on, then illuminate the timing marks with the timing light. Twist the distributor is small increments while observing the timing marks. As the distributor is twisted, the timing marks will move. Continue to twist the distributor until the timing marks line up with each other, then turn the engine off. Tighten the distributor's hold-down bolt with a wrench, then reattach the vacuum line to the side of the distributor. Disconnect the timing light from the engine to complete the process.
