Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Pertronix ignition in a +4 ?

Aside from the lack of need for maintenance that you mention Bill the biggest advantage is gained by the increase in Dwell Angle, just a refresher for you, the Dwell Angle is the angle the points remain closed and its during this period that the coil is charged up, the greater the Dwell the greater (up to the coil max) the firing voltage available. As mechanical points have a period where they physically open and close they 'use' a number of rotational degrees to do this, that reduces the available 'Dwell'. When your using a ferrite rod or light chopper disc there are more degrees of Dwell available.

Other benefits are of course removal of points bounce at higher RPM giving a more accurate ignition timing (as the distributor turns at half crankshaft speed one degree of Dwell variation is equal to 2 degrees of ignition timing change). Lesson over Bill ;-)

Hope your well.
Colin

Well I am alive. Back hurts, not from changing engines but from planting flowers in the front yard. I am told that I must have a "Garden Party" for the "Basic Eight" (Old Friends)

No I had not heard that Dwell was increased with Pertronix. But I wonder if I should care. The Pertronix/points are nothing more than a trigger, as I use a CD Ignition. Remember We are talking about a TR engine, not a Modern engine.

My objection with Pertronix is I can't see what is wrong. But I can with Points. I do have a dual point mallory that I used for some time. Maybe that is the answer to the Dwell issue, as I do not like Pertronix.

Button

As I understand it, the operating mechanism is different between an original Pertronix Ignitor and the Ignitor II/III. Despite ultimately serving the same purpose and looking outwardly similar, they are different enough that (in my admittedly non-expert opinion) we would do well to be clear which one is under discussion at a given time.

While what Button has said may be true of the traditional Ignitor (that it is basically a magnetic switch that replaces a mechanical one) it is not necessarily true of the Ignitor II/III.

These units have "Adaptive Dwell" and actually vary the dwell time based on sensing the charge level in the coil. As a result, what Spanner Juggler has said above about increased dwell time could sometimes be true (giving a higher resistance coil a longer time to "charge" at low RPM), the converse can also be true: Ignitor II/III can actually reduce the dwell time at low RPM to avoid overheating a lower resistance replacement coil.

A lower resistance coil will charge faster, meaning that it will be able to produce a stronger spark at high RPM when the dwell time is necessarily shorter. As the OP was considering replacing both the points and the coil, this difference between the Ignitor and Ignitor II/III may be worthwhile. (Although perhaps the low-revving TR engine would not benefit much?)

All that being said - for the time being my car still runs points so I cannot comment on the reliability of any electronic ignition. I'm also not an expert and gleaned all of the above from reading as opposed to experience, so take it all with a grain of salt.

Well at least You read up on Pertronix. I have not, nor do I know the difference between Pertronix, II or III. I do know that there are well known Mechanics that prefer Pertronix over Points. At least for the TR engine I will stick with Points.

Button

The Pertronix III doesn't use the little magnetic collar and directly senses the cam lobes. It's also a low impedance system so requires a different coil.