Rotor free play

W

wcmill

Member
Hello gents.
I understand all about the slop or free play adjustment on the distributor cam/shaft. Les Andrew’s states all test light on/off adjustments to be made with the distributor cam full clockwise. Other recommends like Nu-wrench basically say the same thing……take out the slop by turning cam clockwise, then tighten down screw.
So my question is, after the engine has been running and you check the position or slop of the rotor, should it be against full clockwise or counterclockwise?
Just can’t get my head wrapped around which it should be. Mine seems to almost be in a neutral or floating position in between the two.
My free play I feel is quite good….maybe 1/4 to 1/2 inch measured at the tip.

Hope this makes sense…..thanks.
 
Hold light pressure clockwise while slightly rotating the engine clockwise from the front to remove slop.
 
Ramen is right the rotor is going to be rotating counter clockwise when the engine is running.So turn clockwise to get the slop out.I always have the spark lever up when I time at top dead center.
 
Thanks for the reply guys.
I don’t think I was very clear with my question. I just want to know if there is a position that the rotor should be in when the car is turned off.
If the rotor moves back and forth let’s say 1/2 to 3/4 of an inch (free play)as it sits on the cam, when the engine actually is running will the rotor be pushed against the cam against the clockwise or counterclockwise position. So when you turn the car off and twist the rotor, should it be up against one position or the other?
I’m sorry I just can’t describe my question any better then that.
 
Rotor could be anywhere within the range of play that it has, depends on how the engine rocks against compression when shut off. It doesn't really matter, the rotor will assume the correct position when the engine is started. :)
 
Wcmill, I too, have thought through your question, although a long time ago. Here's how I think of it:

The face of the driving tooth on the engine cam shaft will immediately move into contact with the driven face of the tooth on the distributor shaft when the car is cranked over. Thus the slop you are seeing will be removed, and will remain so until the motor is no longer running.

What's important to understand, IMHO, is that you want this slop removed BEFORE you completely tighten the distributor cam lock screw as you time the ignition to the engine.

As I remember, if you follow the Nurex instructions shown in the Nurex video on their website, this is accomplished. Again, as I recall, they tell you to partially tighten the cam lock screw just enough so that the serrations on the bottom of the distributor cam will drag across the distributor shaft and thereby remove the slop in the teeth of the two gears. When you stop on the final turn, the slot in the distributor cam will be in the proper place. The points will be JUST ABOUT to open.
 
A distributor can have unnecessary rotor play if you are running a stock two piece distributor shaft that is worn at the slotted ends creating excess play or/and the oil pump distributor drive gear that is driven by the cam is worn. Look these items up in a Model A catalog for pictures. LRF
 
If your rotor rotates up to 3/4" of arc on the cam, I would discard it and get one that fits snug on the cam. In both of my Model A's, the rotor does not rotate on the cam. They rotate with the cam.
 
Last edited:
Bob Bidonde said:
If your rotor will rotates up to 3/4" of arc on the cam, I would discard it and get one that fits snug on the cam. In both of my Model A's, the rotor does not rotate on the cam. They rotate with the cam.
Click to expand...

I didn’t describe that very well, the movement I see on the rotor is the movement of the play in the shaft. The rotor itself is snug on the cam.
 
Thanks for all the replies you guys. The engine is timed and runs very well.
I won’t worry about the position of the rotor as far as play goes once the engine is stopped.
Just one of those “but shouldn’t it do this” questions when you lay awake at night🫤
 
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