How to Time a Chevy Inline 6by Don Bowman
The firing order for a Chevy inline 6 cylinder is 1-5-3-6-2-4, and the timing should be 4 degrees BTDC (before top dead center.) The cylinders are numbered in order from front to back. The initial timing must always be set with the vacuum advance on the distributor disconnected so base timing can be seen. The distributor on a Chevy inline 6-cylinder engine has three stages of timing: base, vacuum advance and centrifugal.
Connect the timing light to the battery by placing the red lead on the positive terminal and the black lead on the negative. Clamp the pickup lead around the first spark plug wire closest to the radiator.
Unplug the vacuum advance hose from the distributor and plug it with a screw so it doesn't leak vacuum.
Start the engine and shine the timing light at the timing chain cover timing plate on the front of the engine. Note where the straight timing line on the harmonic balancer is relative to the 4-degree BTDC mark on the timing plate.
Loosen the hold-down clamp on the distributor using a wrench. Rotate the distributor in whichever direction is needed until the timing mark on the balancer is on the 4-degree BTDC mark on the timing plate. Tighten the distributor hold-down clamp nut with a wrench. Pull the screw out of the vacuum hose and plug the hose on the nipple to the distributor.