Timing twin ignition

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Can someone tell me how to time my 6 cylinder, twin ignition engine? The rotor has offset contact so I’m not sure how to connect the spark plug wires on the 12 hole cap. Thanks.

ron

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Ron As I recall this is a Hercules, or something similar in a 30s Pierce-Arrow truck and not a Pierce 6?

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Yes David, Hercules built the engine. It has two plugs per cylinder, one distributor cap. The rotor contacts are offset (not 180 apart) so I’m not sure how to connect the plugs. Why are there two ignition circuits if the cylinders fire at the same time? Does one set lag behind the other?

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I understand that fire apparatus required twin ignition as a reliability feature. I may be wrong. It was explained to me that is the reason the Pierce-designed V-12 in the Seagraves have two plugs per cylinder in the heads.

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Can someone tell who made these coils? Can they be rewound or are they still available?

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Ron,

I think I have a secondary wiring diagram off of a 6 cyl. Continental that has the same type of distributor, made by Delco. It is a dual ignition. One end of the rotor is offset by one contact in the dist. cap. The coils are different than yours. It is on a fire truck, although not a Seagrave. I am out of the country for another week. I’ll look for it when I get home. Dave

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Ron, Back to your original question, You did not tell us if you have a Model B-6 or C-6 Truck. The ignition coils for both are Delco #2171. They are used on other cars, they should be easier to find than the later truck coils that only fit Pierce trucks.

This Pierce engine should use two caps in line on the same Distributor. A picture would confirm that they have never been replaced with something else. These trucks left the factory with Delco dist.# 5202 or 5216. One has lever adjustment for advance, the other auto advance.

I have the factory procedure to set these distributors. If you check the dist. tag for the above Delco numbers I can get you the correct info. If the tag is different, post it and we can try to figure if the retro-fitted something else to your truck. If you have a later Hercules engine, who knows what’s there! 1924 Pierce 6 uses a single cap on a Delco 5265 Distributor. 1925-6 6 cyl uses Delco 5265 Distributor.1931-33 6 cyl uses Delco 4077. So give me more to go on and I should be able to get your points and timing in spec. Karl

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