Rotor Gap as important as point gap

Afordman31

Afordman31

Well-known member
How to restore your Model A volume 7 has a article by Michael Pawelek, Fulshear, Texas. Page three.
The article states to shim the rotor so it would be parallel to the distributor contact point, he said .035. I made shims for mine and it raised the rotor but the tip would hit under the distributor contact point.
The article said "do not try to bend the tip up as this will either cause it to break or will cause the rotor tip to not be parallel to the contact point."
Has anyone tried to bend theirs or grind the rotor tip shorter or used shims to be parallel and be able to get the .035 gap? I took the shims out and have been running the gap larger than .035.
 
I bent ours to force it to line up with the center of the contacts on the distributor. I then ground some off to widen the gap. perhaps using shims would've been better, I don't know.


The only caution i'd have to give on rotor gap is obviously you don't want too big, but you don't want too small either. My gap was very small at first and a slight movement in the cap caused the rotor to hit a contact.

Honestly i'm not upset I made the mistake. One of the best parts of working on A's is their forgiveness.
 
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The gap between the rotor tip and the four posts in the distributor housing should be set to some "nominal" value and they should all be the same according to most experts. The nominal value, however, is a disputed subject according to who ever is telling the story.

My thinking is that it should be somewhere around .030. Henry probably never had a problem with it as he insisted on quality from his suppliers. Good luck with tody's suppliers. Bending the rotor tip can cause it to easily break and I have tried to avoid doing that. What I have done is try to match a cap up to a given rotor by filing the posts down. Find the post that is the fartherest away from the tip of the rotor and if it is "nominal", file the other three post until they are all the same. Keep the cap and the rotor together as a matched set.

Tom Endy
 
As far as I know, the Model A is the only distributor where you can even check this out?

Never been an issue with any other breaker-point engine I've had; why should it be a concern with the Model A ?
 
Special Coupe Frank
In the article Michael Pawelek states: On the last seven Model A's I looked at, the alignment of the rotor tip and contact points were not only skewed, but also too far apart. Admittedly, the voltage of the spark at this point has been increased tremendously by the coil, but as we know, air is a terrible conductor and the larger the gap, the more voltage it takes to jump it. Let's save the voltage for the spark plugs.
 
Remember at the county fair, some guy had a do-dad he put in the top of a distributor. The engine would come to life from a barely able to run condition.

Well that thing was nothing more that an air gap. It idea being that the coil would build up voltage until it could jump the gap, thus making more voltage at the plugs. The problem to big of an air gap would damage the coil.


Well, Ol' Henry beat them to it with the air gap in the distributor.
 
The gap between the rotor tip and the electrode should be no more that 0.025. Also all 4 gaps should be close to the same size. Some years back there were many repro bodies that the electodes were all over the place in length. Also rotors that pointed everywhich way. If you can find one of those clear dissy caps or make one by cutting the sides of a cap, it is fun to watch the sparks fly in the dissy.
Clem
 
Jerry in Shasta said:
Remember at the county fair, some guy had a do-dad he put in the top of a distributor. The engine would come to life from a barely able to run condition.

Well that thing was nothing more that an air gap. It idea being that the coil would build up voltage until it could jump the gap, thus making more voltage at the plugs. The problem to big of an air gap would damage the coil.


Well, Ol' Henry beat them to it with the air gap in the distributor.
Click to expand...

Do you honestly think other distributors don't have any gap? :p
 
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