Help wanted: Petronix owner with a dwell meter

[Harv]

Ladies and gents,

For my magneto thread (http://www.fbekholden.com/forum/viewtopic.php?f=25&t=20727), I want to do a brief write-up about the Pertronix Ignitor I (often just called a Petronix). I will do a comparison between maggies, dual-point dizzies and Petronix equiped greys.

I have a pretty fair idea of how the Pertonix Ignitor I works, and know that dwell is waaaay different to a standard grey (Pertonix get extra zap in other ways than increasing dwell). Measurements made by some enthusiasts (but not on the grey motor Pertronix 1864a) show dwell is around 27-28º - substantively lower than the factory grey motor 35º to 41º.

I'd like to publish the specific number for the grey - does anyone on the forum have a Pertonix installed who can run a dwell meter over it for me please?

Cheers,
Harv (deputy apprentice sparkplug tester)

[ardiesse]

Harv,

It took me a while, but I put a dwell meter on my FC, which has a Pertronix ignition module:

28 degrees dwell.

I wondered whether the Pertronix units increased the dwell at higher rpm as a way of increasing the spark energy, but no.  There was no apparent change in dwell angle with increasing engine speed.

Rob

[Harv]

Thank Rob - very much appreciated. The PerTronix Ignitor I (grey motor) has fixed dwell - the later model Ignitors have variable dwell.

Can I be a pain please and ask another favour? Can you please measure the gap between the magnet ring and the sensor with a feeler gauge? More gap = more dwell. I have one grey motor data point (33.6º with an air gap of 0.040”) and am guessing that your gap is a little tighter than this.

Cheers, and thanks,
Harv