I thought the crab distributors were pretty bulletproof.

[Mart]

I fired my rebuilt French motor, and had a problem with misfiring, and after a round of changing caps etc, I found the problem to be with the rotor arm. This was a black "made in USA" rotor arm bought either from Macs, but more likely one I got from Napa.

This rotor ran great last year, but this year it just didn't want to work.

The motor would run at a fast idle and then just suddenly stop. After cooling a bit, it would start again. Not the best situation when I wanted to get a good 20 minutes on it to break in the new cam.

A few years ago I went through a round of this with the Lucas rotors, I thought I'd got this licked when I swapped to the Crab.

Anyway, here's a pic.



You can see the burnt/charred/darkened area around the 10 O'Clock position.

And another one.



Harder to see, but the slightly darkened "7" shape inboard of the first leg of the "M" shows the leak path.

So, I post these to alert you all to the possibility of failure, but also to ask is this common? Are these prone to failure? Is there a better one out there? I thought these were the best.

Mart.

[BUBBAS IGNITION]

Mart,


Pretty rare for a black rotor of any brand do that.
I would be very carefull and look at the entire secondary ignition system. Something is calling for a very high voltage demand .
Check the coil wire and all connections, plug wires etc , also a lean ( like in air leak) air fuel will ask for more voltage....

[Bruce Lancaster]

Might be a bad rotor, but first carefully examine cap, wires, and plug gaps...if you have a gap or high resistance somewhere affecting anything from one cylinder to all, it can force a misfire through whatever is the weakest other link.
At least with a crab, phasing should not be a problem...that should be built in right out from the camshaft.

[Mart]

Thanks fellas. I will investigate further.

One thing I did notice, was that when I held a grounded screwdriver blade near each "cap" (actually completely exposed oe ford terminal ends) I got a good fat spark on most leads, but a weak spark on a couple of them.

I need to look carefully at the leads and cap. The plugs were changed for new ones.

Mart.

[OLD...BILL]

Originally Posted by Mart

Thanks fellas. I will investigate further.

One thing I did notice, was that when I held a grounded screwdriver blade near each "cap" (actually completely exposed oe ford terminal ends) I got a good fat spark on most leads, but a weak spark on a couple of them.

I need to look carefully at the leads and cap. The plugs were changed for new ones.

Mart.

Hey Mart; You have a HI-RESISTANCE .... somewhere ?? in the hi voltage side,,, ie, plug wires, cap. the plugs themself, what did you use on the plug threads or to much of it. I assume the inside on the cap and the disturber is clean and dry, can I say supper clean .... and "HOW HOT" is your coil ?? is it grounded / mounted to the engine, or on the fender wall ??.. you have a gasket on/at the cap, and crab. bass to the timing cover, has a gasket. to improve a ground in this area, put a star washer on the two bolts holding the dist on the engine, in place of the lock washer....your rotor may be ok ?? but once a carbon path is found it's there for good. ??
Mark, I have read your treads in the past, I know you will get this fixed, you know what your doing and we will all learn from it ..... thanks ....OLD...BILL

[Terry,OH]

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I had a rebuilt crab distributor give me problems on the road. I changed the entire distributor in a field and got home to find the NOS Ford rotor had done the same and shorted the coil to ground. You can't tell by the Mfg. if the parts are going to be bad when first used. Defective parts are very probably more common on NOS (IMO) than more recent Mfg.

[Mart]

I suppose the lesson learnt is to ALWAYS CARRY SPARES!.

Thanks for the input.

Mart.