FYI- I have noticed in my "Z" that when switching to a optical or Mag
Trigger it does have steadier timing at upper Rev's than points-
Also make sure at least with my Crane Box it does use a different wire for
Points vs. Mag triggers-
John W.
Spitfire #892 DP
240z CP
----- Original Message -----
From: "Joe Curry" <spitlist@cox.net>
To: "'Mark J Bradakis'" <mark@bradakis.com>; <fot@autox.team.net>
Sent: Tuesday, July 01, 2008 11:06 PM
Subject: Re: [Fot] Mallory dual point trouble-shooting
> Mark, you make some good points (pardon the pun). But one of my main
> reasons to used a Pertronix igniter conversion to trigger the MSD was
> because it eliminates that mechanical contact against the cam inside the
> distributor. So there is no wear on that fiber piece that causes (however
> slight) changes in the points gap.
>
> Joe C.
>
> -----Original Message-----
> From: fot-bounces@autox.team.net [mailto:fot-bounces@autox.team.net] On
> Behalf Of Mark J Bradakis
> Sent: Tuesday, July 01, 2008 9:20 PM
> To: fot@autox.team.net
> Subject: Re: [Fot] Mallory dual point trouble-shooting
>
> When you are using a dual point distributor ( or a single point
> one for that matter ) with just a coil you can get a fair amount of
> current flowing through the points. They arc when they open, and
> they arc when they close. That's one benefit of the dual point, one
> set arcs on opening/closing but not on closing/opening because
> the other set is handling the current at that moment. Only half
> as many arcs per point set, so they last twice as long, since
> the arcing is what contributes to the pitting and deterioration
> of the contact surfaces.
>
> With the addition of an electronic box like Mallory, MSD or
> Crane units, the points carry very little current and only provide
> an on/off voltage signal to trigger the electronic box, which does
> the dwell and saturates the coil and such by itself without any
> further help from the points. No arcing to speak of, points last
> basically forever ( Well, in race car years, that is )
>
> I'm guessing that the electronic units in conjunction with a
> dual point distributor can possibly sense the extra close or
> open of the second set of points and get confused, thinking
> that the engine is running half as slow or twice as fast, or
> is an 8 cylinder instead of a 4, or maybe a 2. Hey, it has been
> over a quarter of a century since I took graduate level electrical
> engineering courses, I'm just talking out of my, uh, hat here.
> Suffice it to say that with an external ignition controller, you
> only need one set of points to trigger the timing cycle.
>
> One a sort of related note, I ran a Mallory dual point in
> Killer. I needed a new cap for one weekend. Local speed
> shops had no 4 cylinder ones, so I bought an 8 cylinder one,
> installed it and put the plug wires into every other tower.
> I was amused by the folks who would notice that, and claim
> that there was no way it work, you can't do that, etc.
>
> mjb.
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