ignition rotor

[tahoe healey]

Anyone know about the "new" "premium" rotor form Moss? It appears to still have the rivit but they claim it is built better. I got an expensive one from a company who claims theirs will not break. It disintigrated in 3 feet! Inside tap shattered. They are replacing it but now I don't trust it. Paid $29.00 including shipping. I'm back to using my spare with no back up (it's 6 + years old). Where do I get one I don't have to worry about? I've had two that broke this year and the snow has just melted.

 

[Dave Russell]

Some combinations of caps & rotors will just not work together. If the rotor arm sits too high or the cap contacts are too low, they will contact each other & destruction will occur.

Some rotors set the contact higher than others. Some caps set the cap contacts lower than normal, what ever normal is. There doesn't seem to be any closely controlled dimensions for these parts.

The problem is especially common when a Pertronix timing sleeve is placed over the cam. Of necessity, the sleeve raises the rotor a bit above normal.

You can measure the rotor arm height above the cap seating surface & measure the cap contacts height above the same seating surface on the cap.

A safe margin would be to have the cap contacts 1/16" above the rotor contact. You just have to carefully measure the parts & find a combination that has enough clearance.

If the rotor sits too high, as in the case of the Pertronix timing sleeve which raises the seated rotor position, you can sand off part of the rotor bottom seating surface to let it sit lower & gain more clearance.

This will also work with the standard points set up if needed.

Occasionally, you have to find a different cap that has the contacts mounted higher. Another possibility is that the distributor shaft has too much end play & lets the rotor rise too high in the distributor. End play should be no more than 0.002", as should side play.

Once you find the required rotor height to give clearance, make sure that all spare rotors have the same dimension.

In your case, measuring the "good" rotor tip height above it's lower seating surface & duplicating it with the spares should work, at least until you change caps. DO make sure that the rotor is firmly seated all of the way down.
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PS - It's strange that the parts makers never seem to mention these possible problems but just keep you replacing parts.
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