Distributor control interchangeability

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Distributor control interchangeability

Unread post by Vzike » April 7th, 2021, 2:02 pm

I've been rebuilding distributors and have been asked several questions from guys. One of the big issues is on the interchangeability of the controls and the cam on the top of the distributor shafts. Today I was pointed back at an old G503 post from 2016, as a reference to why... what ... etc....

I believe I'm correct on all of this, so I'm posting it here.

My post on the G503 follows:

I know this is an old thread, but I received a message from someone who referenced this thread.

Here is my two cents worth.

I have distributors with three types of cams condition. One, has NO Cam. Some have a smooth 4 lobed cam. The last style has 4 sharpely stepped lobes.

The points distributors require a smooth, four lobed cam, which opens and closes the contacts, when the distributor spins. A plastic "finger" on the moving part of the contact arm remains in contact by spring force on the cam. I have many points distributors, and all have smooth lobes.
* If the lobes are missing, the points will never actuate.
* If the lobes have sharp edges, they "finger" will be ripped off, and the points will not actuate.

Prestolite control distributors have a sharply stepped 4 lobed cam. The sensor on the Prestolite control senses the steps in the lobes, and triggers the ignition. It is a simple "ON/OFF' trigger. These require that sharply stepped cam. The smooth one will not work and one without lobes will not work. The original kits that came with the Prestolite control conversion kits, had that replacement top piece with that correct sharply stepped cam on it.

The Swiss controls are like that Honey Badger. It don't care!!! The sensor to actuate the ignition faces up and is away from the cam all together. The ignition is actuated by the gaps in the ROTOR as it passes through the sensors. That is why you must have the correct ROTOR when swapping out from a points or distributor with a Prestolite control. The Swiss control kits contained the ROTOR, but no cam part.

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