rotor problem
 

I thought I would share my rotor story our 28 has always ran good until a condenser went bad last week got a new one from snyders and thats all fixed but I could not get the car to idle as low or smooth as it should after hours of playing with the points switching and cleaning all the old spark plugs.had the carb apart 3 times even switched coils than I tried a old rotor thats been under the seat probley 60 years and what a difference! it idles down nice and low and smooth! the old rotor looks good. never seen this problem before, I would never have replaced it but I tried everything else and it was there.

Re: rotor problem
 

Is there a difference in gaps between rotors ?

Re: rotor problem
 

I've seen this problem before with distributor bodies and rotors with either too much gap or the distributor body not having all 4 contacts with the same gap. When I checked the gap on mine shortly after I got it, the gap was over .100 on all 4 contacts. I don't know how it ever managed to run.

Re: rotor problem
 

I've also seen rotors short to the shaft they set on.

Re: rotor problem
 

Looking at both rotors same gap about .020 both a little loose on dist shaft i will check with a ohmmeter

Re: rotor problem
 

Re: rotor problem
 

Not sure now! I think the one on left is the good one. I have seen lots of bad rotors on electronic ignition burn thru it was common with gm hei . This one fooled me! I'm not a parts changer when I change a part it's bad nothing I hate worse than working on car someone else screwed up by changing parts that weren't needed then telling you they did all the hard part all you have to do is get it running!

Re: rotor problem
 

I wrote a article some 25 years back for The Restorer Magazine after having the same rotor and distributor body problem. As the rotor turns you will get a more consistent spark if the rotor gap to body lugs are similiar and if the leading edge of the rotor is in the same plane as the lugs. To use my current body and rotor I have had to install a tiny rubber washer under the rotor to raise it a tiny bit. I have always been Leary of trying to bend the rotor up or down as the non metal part of the rotor is so brittle.

Re: rotor problem
 

The rotor on the left looks burned away on the advanced position. When the spark lever is advanced, the spark will jump from the right side of the tip in your picture.

If a rotor is too loose I push it on over a small piece of paper.

Re: rotor problem
 

Could it be carbon build up? High energy loves to travel through the stuff. Try cleaning with a scrubby and wd40 followed with brake clean to dry to see if it does anything.

Re: rotor problem
 

Good advice Texas and Tom I never thought about adjusting the rotor I will look closer at how it lines up the dust cap is even all the way around not worn excessively that's a nice thing with the model a other cars you can't see the gap

Re: rotor problem
 

From the looks of both rotors, I think your carbon in the cap may be worn away and making the spark jump a gap. Sparks is what causes the burn marks I see where you should have a shiny spot from the carbon rubbing. Time for new rotors and a new cap.

Re: rotor problem
 

I noticed that mine was a little low and was able to bend it up very slightly. This had the effect of closing the gap slightly also. Did it run better? I don't know, maybe, It sure wasn't worse!
Terry

Re: rotor problem
 

According to Galvin radio in the notes for installing a radio in the Model A Ford...

The gap between the rotor and cap varies a lot in the Model A Ford. Peen or solder the end to get the gap under .005" to reduce radio noise.

It is also recommended to connect the spark rod to a cylinder head bolt with a wire. The Electrolux cable might also need to be bonded to prevent noise.

Ya, not an answer to the question, but an interesting tidbit...

Re: rotor problem
 

I`m with Tom, it looks like your carbon under your cap is worn out or coming apart. it should not be burning the rotor like that.

Re: rotor problem
 

Did you use a feeler gauge and install both rotors again to check the end gap.

Re: rotor problem
 

I ALWAYS replace the rotor with a tune up! They take a beating & they're CHEEP! IF spark has been arcing through it, it leaves a RAINBOW looking discoloration, up inside the hole. Just hold it in the SUN & look for yourself!
DON'T keep OLD ones in your spares, THROW THE DANGED THING AWAY!
Bill Missing

Re: rotor problem
 

Found the rivet holding the rotor tip loose, peened it a bit to tighten, BIG difference in performance. FWIW
Paul in CT

Re: rotor problem
 

Yesterday the motor started to misfire a bit - not too bad. We went up a 1 in 3 hill in second gear without too much trouble. On inspection the rivet on the rotor had come lose and the brass contact had dropped off, conveniently lodging in the dizzy body without shorting anything. This gave me a spark gap of almost 1/2 inch and it was still running - so I don't think the spark gap is your problem! I have flooded the top of the new rotor with solder over the rivet to hopefully add a bit of life to the new one.
btw - I only had a wheel nut wrench in the car but was able to use it to peen the rivet to secure the tip of the rotor and drove 30 miles home without a single misfire.

Re: rotor problem
 

ALWAYS keep NEW rotors in "STOCK", they're CHEEP!--Throw the OLD ones AWAY!
Bill W.