Harmon Collins Dual Coil "Crab" distributor

The Harmon Collins Model 14 distributor was based on the Ford "Crab" distributor with modifications that essentially turned it into two 4 cylinder ignitions operated by a single shaft with one four lobe cam. This lengthened the time available to fully saturate the ignition coils with current and therefore to deliver maximum spark at higher RPM's. Two independant sets of points mounted 45 degrees apart triggered two coils. The Ford points plate was stripped of normal hrdware and drilled to mount the points. This required one end of the "bridge" that held the front bushing to be trimmed of its mounting foot and rivets. It was then welded to the plate on the bottom side.

The intermediate plate and the special rotor connects the second coil to the renumbered distributor cap.

The points are special. These were somewhat burnt and pitted but were cleaned up with an oil stone.

This distributor had been in a box for ever. I finally decided to clean it up and see if I could repair the broken spark plug tower on the lower left of the cap.

I had a extra cap that I cut a tower off of and filed it to fit the H&C cap as best I could. I made a nylon plug to fit the wire terminal and what was left of the broken tower of the H&C cap. This aligned the new piece while the epoxy cured.After the first application of the JB Weld epoxy, the joints were sanded and covered with a black epoxy I found at a craft store. Note the circular ring worn into the cap by the rotor. This was addressed below.

The interference between the rotor and the inside of the cap was determined to be caused by the flat on the shaft to be too short. The length of the flat was .150", while on another distributor was .180". The flat was lengthened .030" which fixed the problem. The rotor mounting adapter now sat lower and allowed the rotor to clear the cap.

The rotor adapter:

Another repair was needed to the intermediate plate where the locating tab or key was broken off. I milled a small slot where the key had been, then epoxied a new key in. The key was made from a piece of epoxy fiberglass board.

Inside of the shaft is a wick that is soaked in oil to lubricate the small bushing at the front. There is a small hole that feeds oil to the bushing. The wick is accessed by removing the plug at the rear of the shaft. I drilled the plug and tapped it for a 10-32 thread, then pulled it out with a screw and some washers. Then I made a new plug threaded 1/4-20 and used a hex set screw for easier access for future lubrication.

Another problem I found after inspecting the distributor housing closely was that the two mounting holes had been drilled oversize for some reason. The holes in two stock distributors measured 21/64 for the upper hole and 11/32 in the lower hole. The smaller diameter in the upper hole is obviously meant to position the distributor accurately after it has been set up off the engine and then installed to insure that the timing will be as close as possible. I made 1/2-20 threaded plugs and Loctited them in the oversized holes that I tapped the same . There was an adaptor plate that came with the H&C distributor that would make it possible to use it on earlier engines made for three or four bolt distributors. The adaptor had two holes drilled and tapped for the two bolts on the H&C and '42 to '48 Ford distributors. I used the plate to center punch the plugs I installed in the oversized holes.

I made this transfer punch to mark the centers of the new holes. The threads were cut and the point turned in one set-up so as to make the center mark as accurate as possible.

Here is the housing bolted to the adaptor which made me happy that the holes lined up well. I also checked the fit of two other distributors in the adaptor to verify that the holes in the adaptor were placed accurately.

The Mallory condensers that came with this distributor have cracks in the part of the brass housing that is crimped around the plastic (Bakelite?) end piece. The capacitance on both of them measured around .42 microfarads so they may work just fine, although I would be concerned that moisture might get in them. If I were going to use them I would try to seal those cracks with some sort of runny epoxy that would wick into that crimped area.

A somewhat fuzzy copy of the instruction sheet:

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Created on.... November 17th, 2013

Updated on.... June 3rd,2014