How to use a timing light and adjust timing

1. Make sure the engine is off and the key is removed from the ignition.

2. Clamp the red clip to the positive terminal of your car battery.

3. Clamp the black clip to the negative terminal of your car battery.

4. The larger clip with the thickest insulation goes on your #1 spark plug wire by attaching the clip around the wire that leads to your #1 spark plug.

5. Next, you will want to rotate the lower crankshaft pulley so that the timing marks are visible on the crankshaft pulley. Be aware that on some cars the timing marks are located somewhere else and you should consult either your owner's manual or dealership.

6. Your automobile specifications sheet should tell you what your timing degree should be. For example:

1969 Ford 429
6 Degrees BTDC @ 550 rpm in drive gear
Automatic Trans
Firing order: 1-5-4-2-6-3-7-8

This means that you want to line up the pointer on the timing light with the 6° timing mark when the engine is idling in gear at 550 rpm. "BTDC" means Before Top Dead Center and "ATDC" means After Top Dead Center - top dead center is the point where the piston reaches the highest point in the cylinder and that is when the compression is the greatest.

The timing marks will have a line labeled "0" with marks above and below it, and depending on which way the wheel rotates, you will see the lines before the "0" (BTDC), or after the "0" (ATDC).

7. If you want, you can use some chalk to mark the timing marks to make them more visible. If there is a rubber hose on the side of the distributor, disconnect the rubber hose from the vacuum advance and put a plug in the end of the hose to seal it off temporarily.

8. Okay, now start up your engine, letting it warm up.

9. Take your timing light and aim it at the timing marks, pressing the button on the light. Because you have the light hooked up to your spark plug means that it has current passing through it every time your spark plug fires, making the light go on and off, creating a strobe effect. Because of this, the timing marks should appear to be standing still. Now, is the pointer pointing at the correct mark? If yes, you are all set, you do not need to adjust your timing. If it is not, you should adjust your timing.

10. Adjust the Timing by looking below the distributor, at the base of your distributor shaft, for a fastener called the distributor hold-down clamp. We want to loosen this fastener so the distributor can turn on the shaft. Grasp the vacuum advance and move it back and forth.

11. Rotate the distributor slightly, and then aim your timing light back at the timing marks again. How does it look? If it is farther away from the marks, then move the distributor in the opposite direction. Then, check again with your timing light. Continue doing this until the pointer is pointing at the correct degree point as required.

12. Once the timing is good, tighten the fastener for the distributor hold-down clamp, making sure you do not move the distributor. After tightening this fastener, double check your timing to ensure it is still correct.

13. Turn off your engine, remove the key from the ignition, and disconnect the timing light.