Which Rotor Arm for Electronic Ignition.

[Dan Smith]

Hi,

I purchased a Proform Electronic Distributor Kit 66993 from Summit Racing and it appears that the rotor arm supplied in the kit is incorrect in the kit.

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It appears to be not long enough by about 1/8 of an inch and only just sparks at the edge of the cap contacts. I have checked the one Zac Marshall has it his is the correct longer one. I ordered a replacement from Martin Robey Part 3874401 (White original, Blue Martin Robey, Black Zacs, the correct one) which is the same as my original one. Question is what is the correct part and where can I get one ideally before Friday and the CV8 60th Weekend? I have new rotor and cap coming from Summit in 2 weeks but as said would like one sooner.

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Point of spark is just on inner edge of contact.
Thanks in advance
Dan.
CV8

[VFK44]

Out of interest, does it work? The spark is meant to jump a cross a gap anyway, so an extra 1/8" might not stop it working. Presumably there is a risk of damaging the electronics if you run too long like that.

[Dan Smith]

Hi,
It currently does work but when it gets very hot it does run rough on idle. Just need to get this right and eliminate this issue.

Cheers
Dan

[johnw]

All three rotor arms look correct and clones of the original Mopar part, so nothing special. I agree the black one looks a little suspect but unless it runs better when hot with the others I would not bother too much. The blue one is presumably a clone of a Blue Streak rotor arm. They were typically blue, so some off brand has copied that. The rotor arm off your old mechanical distributor should work with the new one by the looks. Perhaps the problem is something other than the rotor arm.

[Dan Smith]

John,

The black one is 1/8" longer and so the correct one for my application. Unfortunately it is Zac's and he does not want to give it to me! I need to know if there is a part number for this longer one.

Cheers
Dan

[slotcarone]

What is wrong with your original rotor? Clean the contact tip and you should be all set. The idle problem is most likely not being caused by the rotor.

[Martin R]

John,

The black one is 1/8" longer and so the correct one for my application. Unfortunately it is Zac's and he does not want to give it to me! I need to know if there is a part number for this longer one.

Cheers
Dan

How long actually is he one you'd like?
I can check whatever I have as a spare, just in case.

[Steve Payne]

The Blue one is usually the best one to use. The White ones can be unreliable in my experience. I have had several of these cause rough running.
If the car is running rough once hot I would check the voltage at the ballast resistor and coil once it has been running for a while. A spark should be able to jump 20mm in fresh air so a small gap is never usually a problem.

Steve