Distributor Rotor

Bruce of MN

Bruce of MN

Well-known member
I took the cap off my distributor to check the resistance between the points block and chassis ground per a current thread (~1 ohm) . When I was putting the rotor back on * , I noticed that the brass piece was slightly loose. When I got out the rotor from my backup dizzy, it was loose, too! The plastic next to the brass piece was chipped on both, too. I tightened the rivets on both, but will get new rotors.

Is this a common fault with repro parts?

* I have to confess that I have forgotten to put the rotor back on a couple times.:D
 
Bruce of MN said:
I took the cap off my distributor to check the resistance between the points block and chassis ground per a current thread (~1 ohm) . When I was putting the rotor back on * , I noticed that the brass piece was slightly loose. When I got out the rotor from my backup dizzy, it was loose, too! The plastic next to the brass piece was chipped on both, too. I tightened the rivets on both, but will get new rotors.

Is this a common fault with repro parts?

* I have to confess that I have forgotten to put the rotor back on a couple times.:D
Click to expand...

I have not noticed an issue with the reproduction rotors. Ensure your rotor isn't coming in contact with the body terminals tho. I have seen this. Clearance should be ~.025"
 
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Lift the cap and measure the clearance and make sure the shaft is not loose in the bushings. If all is ok but too little clearance, file off some from the rotor.
 
I've noticed that the rotor tip to contact gap is too large on some rotor/distributor body combinations. Even bending the rotor tip cannot close the gap to .025". These are as much as .060". Not sure, but I tried several different rotors. The distributor bodies may be the problem. Its something to watch for.
 
I've also seen the gap too wide. My solution was to solder on a piece of brass shim to the top of the rotor to close it, then file it.
 
Synchro909 said:
I've also seen the gap too wide. My solution was to solder on a piece of brass shim to the top of the rotor to close it, then file it.
Click to expand...

I've thought about doing the same thing. The one on my '31 pickup has a .035" gap and runs well. But all my others are way larger.
 
I found a housing that was loose on the distributor so that it moved around, changing the gap and making the gap different for the different terminals. I found that the ignition was better with a smaller gap. I try to run around 0.020 inch. I bend the brass part to change the gap.
 
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I have found that there can be a fair amount of difference in the gap between each of the contacts inside of the new distributor bodies and new rotors. I will adjust the rotor to .025" on the one with the largest gap and then file the others to match. Then, I keep the rotor and body together (even those carried as spares).
 
FYI - This is a new body and rotor from a well known major vendor. I bent the tip a little more and got the gap down to about .040". I also tried an old, unused original Niehoff rotor with the same results. I think the repro body contacts are a little short.
 

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Back to the original question, Bruce, are there any signs of being too little clearance and the rotor hitting the terminals, causing the plastic to chip?
 
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