Crab distributor rotor broke?????

O

Ohc Joe

Senior Member
So wired up the 36 really quick to hear her run before I move on to front end stuff..
Turned over for awhile
Couple times back n forth and nothing
No spark
Remove distributor cap and rotor was broke in half
37 block with crab style cap N rotor all new parts from CG ford parts in Escondido cali
I installed the pertronix unit in there
It's all the way in and spring ring is in there rotor went in smooth no issues
Just strange
Thought I'd post to see if any thoughts or past stories..
Thanks guys
Let me look for the pics
 

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Wrong rotor? The 42 and the 46 to 48 are slightly different even though they look the same. One is slightly bigger.
 
When installing a new rotor be sure everything clears properly. Spin it over in your hand and make certain everything clears before installing it on the engine. Don't ask me how I know that.
 
Some of the crabs caps slightly interfere with the rotor usually just one maybe two of the terminals. Rotate the distributor with the rotor and cap in place to find interference before installing the distributor. Slightly file the terminals that the rotor hits removing only enough for clearance. Don't file the rotor.
 
Joe, unfortunately this has become more common. Current rotors/caps can have clearance problems that break rotors. The latest one I worked on had the rotor touching all the cap terminals and I had to file .020" off the rotor contact to make it work.
 
Sounds like the rotor, or more rarely the cap, where not on proper or as suggested the rotor may not have been the correct part. The fellows here who rebuild crab (and other) distributors usually check the clearance between the rotor tip and the terminals inside the cap and file-down the rotor tip if to little. Too much clearance and it inhibits the transmission of the spark. Adding a side remark, my '47 came with a pentronix unit and it failed. Spent a lot of money replacing them twice. They always failed when I was far from home. They kept failing and the experts couldn't trace the faults except to note that the failures were probably due to under and over voltage situations. I had the distributor rebuilt back to using points instead an no problems. Like they say "points will always get you home" .... maybe not always but "Usually'.
 
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Good morning guys wow that's crazy I was thinking maybe the housing on the petronics unit might be a little too thick where the rotor slides over I will look into all of that I ordered a cap and rotor I'll keep you guys posted thank you
 
well got new rotor removed distributor
turned rotor by hand with cap installed and it’s definitely hitting
so sanded contacts inside cap a bit also rotor back n forth till she spun freely
installed it all back and she fired up for the first time in along time
now the radiator madness happens
hopefully tomorrow
thanks guys
 
There are tight tolerance to maintain between the rotor and the cap terminals. If the rotor touches one or two cap terminals file them so there is clearance, file the rotor and you increase the gap between all the cap terminals.
 
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