A question of distributor rotor arm positioning............

[mark030358]

Gents,
Just a quick question.

When fitting the dizzy and aligning the rotor arm,should the centre of the rotor arm point to the centre of the dizzy cap No1 electrode at top dead centre or should the centre of the rotor arm point to the centre of the dizzy cap No1 electrode at the static timing figure.

And what margin of positional error is acceptable?

thanks
Mark

[type26owner]

Mark,
Actually the leading edge of the rotor's metal conductor will just slightly overlap the leading of the post in the cap if the timing of the spark via points or whatever is phased correctly at zero rpms. That leading edge is a sharp point to help the spark to jump the air gap. Has something to do with increasing the field effect of high voltage electrodes. The trailing edge has a large radius to gently increase the air gap to break off the current flow if the dwell is too long. Same goes for the spark plug's center electrode when it's new the electrode face is ground flat to be as sharp as possible on the better grade plugs.

That overlapped position is phased by orienting the dizzy body to the static intial timing. It helps to grind through openings into the side of a cap so you can observe this stuff first-hand with a timing light. It's the first thing I do to a dizzy which needs attention and I don't know it.