Firing order needed

1-8-4-3-6-5-7-2

The distributor can only be dropped into place in one of two ways because the end of the shaft looks like the end of a flat-blade screwdriver. It used to be customary to drop in the camshaft's distributor drive gear such that when the distributor was dropped in on top of that gear, the rotor was pointing to cylinder # 1 when that piston was at top dead center on the compression stroke, then that spark plug wire was inserted into the cap right above the tip of the rotor.

To say that a different way, it was normal to find spark plug wire # 1 where this drawing shows wire # 7, then the rest still go in order around the cap. That was more important on older vehicles because the distributors had a vacuum advance unit hanging on the side, and if the drive gear was off by more than a few teeth, that advance unit could bump up against the firewall. You don't have that advance assembly to worry about, so the drive gear can be installed in any orientation. You would still bring piston # 1 up to top dead center on the compression stroke, look where the tip of the rotor is, then install the distributor cap and plug in wire # 1 right over it.

Allow me to make one more comment of great value. You'll notice cylinders 5 and 7 are right next to each other physically, and in the firing order. The very high current that pulses through the spark plug wires sets up an electromagnetic field around the wires, and that can "induce" voltage, and possibly a spark, in an adjacent wire. In extreme cases that can cause a spark in cylinder 7 that is way too early. One of our local racing legends blew up two $25,000.00 stock car engines in the early '80s due to this before they figured out the cause. The early spark ignited the fuel in the cylinder while the piston was still on its way up, and the power pulses forced it back down the wrong way, causing the piston and / or connecting rod to break.

You'll find a small bracket attached to the rear of the valve cover with a holder to clip the spark plug wires into. Most people insert the wires in an order that keeps them looking pretty, but to prevent this spark-jumping problem, the correct way is to separate the wires for cylinders 5 and 7 as much as possible from each other. That means putting one of them on one end of the holder, and the other one on the other end. The wires for cylinders 1 and 3 go in the middle.

Related to this, that spark-jumping is more likely to occur when two or more wires are run alongside each other. The better practice is to have them cross over each other at right angles whenever possible.