How to Set the Timing on a 1989 Corvette

by Lee Sallings

Setting the ignition timing in the 1989 Corvette is similar to other GM V-8 engines. The Tuned Port Injection system and on-board computer controls will change the timing advance during engine operation according to engine load. However, accurate timing control relies on an accurate base timing adjustment. Base timing in this car is set by eliminating computer control temporarily to prevent the computer from changing the timing as you adjust it. This adjustment typically is made as part of a routine tune-up and is well within the average home mechanic's abilities.

Step 1

Apply the parking brake and place wheel chocks in front of the front wheels. Start the engine, and run it at idle until the engine warms and normal idle speed is reached. Turn off the engine.

Step 2

Disconnect the Electronic Spark Timing (EST) connector located on the wiring harness. In the Corvette, this is a single wire connector, with a tan and black wire, that is taped to the wiring harness between the brake master cylinder and the driver side valve cover.

Step 3

Attach the timing light power cord to the battery terminals and the inductive pickup to the number one spark plug wire. The number one spark plug wire in the Corvette is the front wire on the driver side of the engine.

Step 4

Start the engine and place the transmission in neutral (manual transmissions) or drive (automatic transmissions). Aim the timing light at the timing tab on the front of the timing cover just above the harmonic balancer. Loosen the distributor bolt at the base of the distributor and rotate the distributor to adjust the timing to 6 degrees. The timing mark will line up with the notch in the tab marked "6" when this is done correctly.

Step 5

Tighten the distributor and turn the engine off. Reconnect the EST connector. Disconnect the negative battery cable, using an 8 mm wrench, for five minutes. Reconnect the cable and test drive the Corvette.

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