GM firing orders

by: Alittle1, Cobalt327, Jon
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Overview

Firing orders for GM engines.

Chevrolet

• In the case of reverse rotation marine engines where the distributor rotation is opposite of a standard rotation engine, the reverse rotation firing order becomes 1-2-7-5-6-3-4-8.

Be sure on the Chevy V8 that the #5 and #7 wires aren't accidentally transposed. They are next to each other in the firing order as well as at the cylinder head, so be careful.

Buick

Buick V8

• The 1970 Buick 350 ci engine has a firing order of 1-8-4-3-6-5-7-2 and the rotor spins counterclockwise. The number 1 distributor cap terminal is at 5 o'clock viewed from in front of the car.
• 1963-'66 401 and 425 ci Buick engines have a firing order 1-2-7-8-4-5-6-3 and the rotor spins clockwise. The number 1 distributor cap terminal is between 8 and 9 o'clock viewed from in front of the car.
• The 1964-'66 300 and 340 ci Buick engines have a firing order of 1-8-4-3-6-5-7-2 and the rotor spins clockwise. The number distributor cap terminal is at the 4 o'clock position viewed from in front of the car.

Buick V6

Oldsmobile

Pontiac

Cadillac

331, 365, and 390 V-8 1962-back

1962-back 331, 365, and 390 ci with counterclockwise distributor rotation.

390, and 429 ci 1963-up

• 1-8-7-2-6-5-4-3
• Clockwise rotation

368, 425, 472, and 500 ci 1968-up

• 1-5-6-3-4-2-7-8
• Clockwise rotation

4.1L and 4.5L

4.1 and 4.5 L

Northstar

• 1-2-7-3-4-5-6-8