1927 American LaFrance firetruck with 6 cylinder Buick engine

[27alf]

I have a firetruck with a large Buick engine. It was running fine until last year when the engine started running ruff. I went to replace plugs, wires, and points. I was surprised by a duel point ignition system with a 3 lobe cam. I expected a 6 lobe cam and a single point distributer. Well, needles to say I can't figure how to time it or set the points. Anyone with any knowledge of this system that could pass along information, it would be very helpful. Thank you in advance for anything you may have. I also wondered if a newer distributer would fit. 

[Bloo]

How many ignition coils? Does it take two whole turns of the crank to get one turn of the distributor? Most cars do. With 3 lobes though, it wouldn't necessarily have to. Got a pic of the inside of the distributor?

 

These days getting someone to put it on a distributor machine is the easiest, fastest and best. Back in the day it would have been done with a tool that measures the angle difference between the 2 sets of points. Then, timing for the whole engine would have been set with a test light in the normal way for the time, aligning the mark to the spot where the points open and the light changes. A timing light also works and might be better. Without seeing it I am flying by the seat of my pants.

 

Dual points in a prewar context can mean a whole bunch of different things. It almost never the means the same type of dual point system used in the postwar era that so many mechanics are familiar with.

 

Edited December 8, 2023 by Bloo (see edit history)

[joe_padavano]

Dual points and three lobes on a six means that each set of points fires every other cylinder in the firing order. Bloo is right, there have to be two coils. As far as the points are concerned, each set is firing a three cylinder engine. You essentially have two concentric three cylinder distributors in a common housing. You can check dwell for each set of points independently by using a dwellmeter on the six cylinder setting and multiply by 2. Timing only cares about the no. 1 plug, not the number of sets of points, as Bloo noted.

 

This dual point/dual coil/half the number of lobes type of distributor is not that unusual. Ferrari used it, as did Holden for racing distributors. This is the modern Holden version.

 

Edited December 8, 2023 by joe_padavano (see edit history)