Ignition and Timing

This shows the essential parts of the stock factory ignition setup. The computer is between the distributor and the ignition module, allowing it to play tricks with the spark timing while it controls the fuel mixture too.

Setting the Timing

The engine should be completely warmed up.

Disconnect and plug the vacuum hose at the distributor.

Unplug the three-wire connector at the 10" and 4" Vacuum Switch Assembly.

Loosen the hold-down bolt and rotate the distributor to set the timing.

		BTDC	@ RPM
6-cylinder 4.3L	50 States	9° (± 2°)	1600
6-cylinder 4.3L	High Altitude	16° (± 2°)	1600
4-cylinder 2.5L	50 States	12° (± 1°)	1600
4-cylinder 2.5L	High Altitude	19° (± 1°)	1600

Standing at the left fender, looking down at the front of the engine, the timing plate marks can be seen, but the degree number markings are hidden from view by the water pump. You can see them using a small mirror and a flashlight (with the engine stopped of course). The first large mark on the scale is zero, the next large mark is 4, the next is 8, etc. This drawing shows the timing at 19° BTDC.
Once the timing is set, don't forget to reconnect the vacuum hose at the distributor and the connector at the vacuum switch assembly.

Ignition and Timing

Setting the Timing

Table of Contents