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Old 07-21-2018, 07:50 PM   #5
Charlie ny
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Join Date: May 2010
Posts: 3,019
Default Re: Broken rotor on crab distributor

I received a bunch of emails on my reply to 34 so bear with me.........
The following is for any front mounted distributor I build......
After disassembly and cleaning I machine the diameter on the rotor shaft that spins in the big bronze bushing. I turn this diameter to a full cleanup to eliminate taper and out of round, needless to say this diameter is already worn under size. The old bronze bushing is removed from the housing and a fresh bushing is installed, the fresh bushing is .060 undersize on the inside diameter. Now dealing with the 'crab' dist I need to know which cap will be used. The crab cap mounts over the register diameter on the housing and the rabbit ear cap mounts on the inside register diameter. I grab the crab
dist housing in a very accurate 6 jaw chuck on the appropriate register diam and bore the undersize bushing for an .0008 to .001 running fit on the machined rotor shaft. Because I trust my machine ( so far so good ) I am certain that the rotor shaft will be spinning in
truth with the cap register diameter on the housing.
Next
The breaker plate with the outboard support bushing is chucked up in the

6 jaw chuck and I indicate the bushing for runout. Runout here is usually .010 to .020.
In many cases I can true up this bushing using a small brass drift and a small hammer
thunking it in to .002 or less. Sometimes of course more serious lathe work is required


My thinking is it is no use to install a new standard size bushing and expect
to accomplish anything when the rotor shaft is worn .007 or .008.

I have yet to see a used housing where the cap register diameter was even
close in concentricity to the bushing diameter.
I took Bubba's advice a longtime ago and use only NAPA Echlin ignition goods.
Charlie ny
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