Distributor question

A

aermotor

Well-known member
2 model A Fords, one with an original distributor and the other with a Mallory centrifugal advance. The original distributor spark advance/retard is controlled by moving the points and the Mallory advance/retard is controlled moving the distributor cam with centrifugal weights. What allows the distributor cam to move with the centrifugal distributor when it is mechanically driven the same way?

John
 
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I'm not sure that I understand your question.. as you seem to have answered how they work in your question.

In the original A distributor, the cam is attached directly to the distributor shaft. Timing is adjusted by rotating the plate that the points are attached to, thus advancing or retarding the spark by moving the points in relation to the cam. Max advance is controlled by the opening in the bakelite distributor cover.

In the Mallory and later Ford distributors, the distributor shaft is connected to and spin centrifugal weights, not the cam. The cam is connected to the centrifugal weights with a plate that advances with increased speed of the distributor shaft. The position of the points is stationary. Max advance is controlled by the max travel of the centrifugal weights, limited by slots in the plate that the cam is attached to.

The mechanics are understandable if you have an opportunity to take one apart. Great Info on the Model B distributor is available on the Model A Ford Garage http://www.fordgarage.com/pages/bdistributoradvance.htm
 
GRutter said:
I'm not sure that I understand your question.. as you seem to have answered how they work in your question.

The mechanics are understandable if you have an opportunity to take one apart. Great Info on the Model B distributor is available on the Model A Ford Garage http://www.fordgarage.com/pages/bdistributoradvance.htm
Click to expand...

Got it now. The link answered my question. With out taking the distributor apart it appears that the shaft is solid between the drive and the cam. Thanks.

John
 
I am confused as to what problem I had or have. The car wouldn't start - kicked back like it was advanced although it was starting fine. I took the dist. cap off and could move the rotor back and forth even though it felt rough. I removed the distributor and everything seemed fine. Holding the drive shaft the cam won't move by hand. I did not turn the engine over so I should be able to drop the distributor back in and be in time? What caused the rotor to turn by hand with the dist. in the car and not out? Could a weight have hung up and healed it's self or don' I know what I am doing? What is my next move?

John
 
I think you were feeling what is called back lash when it was in the car. That is just a little play between the shaft tangs and also the drive gear. Some cars have more than others depending on wear.
 
If you're referring to the Original A distributor, then it is just backlash in the gears.
If you're referring to the Mallory, you are working the advance mechanism. Check that the springs are returning the centrifugal weights and that they can move freely.
 
GRutter - I have to complement you on your description of original and mallory unit workings. Very articulate and easy to follow you. You communicate well. Post more often...
 
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