Re: MSD/ Ballest resistor

[jlandry@domain.elided (John A. Landry)]

In a brilliant stroke of genius, Mark A Pepe <mpepe@domain.elided> blurted
out:

>On my 76 traveler, the previous owner switched the distributer to points,
>(I have no idea why) anyway, does this mean I should get the ballast
>resistor with my MSD? As far as I know, it doesn't have one but I've been

Mark,

You only need a ballast resistor if you are running your ignition system
*exclusively* off of the breaker-points.  You see, the ballast resistor is
supposed to be there to lower the amount of voltage which passes through
the breaker-points when the engine is running.  This keeps them from
burning and wearing out prematurely.  The starting circuit of the vehicle
is usually wired so that the ballast resistor is bypassed during the
starting cycle.  This puts full battery voltage through the points (and of
course the coil) so the starting spark will be hotter (higher voltage) and
as a result, starting will be easier.

In your case, you're merely using the points as a low current switch (or
t"trigger") to signal the MSD box when to drive the coil.  If this is all
you plan to do, then you will never need a ballast resistor.  However,
should you find yourself stranded with a failed MSD box, you *will* want to
use those breaker-points.  Not having a properly wired ballast resistor
means your points won't last long should you have to use them exclusively.
They would probably last long enough to get you home though.

I retrofitted my 76 with a breaker-point distributor and added a ballast
resistor, just so I could run points to trigger my MSD and have the
breaker-points as a fall back in an emergency.  The FAQ on the Binder
Bulletin web site has step by step instructions on retrofitting to
breaker-points and how to add the ballast resistor (if you care to).

>wires, replacing cap and rotor and just about everything I decided to get
>out the dwell meter- Doh! the dwell had slipped. supposed to be  29-32
>degrees, it was actually at 45. I reset it and the motor turned right over
>and purred away!)

This is one of the shortcomings of breaker-points.  The rubbing block
(which rides on the cam) wears and causes your dwell to increase and your
timing to change.  It's a good practice to check the dwell and timing every
oil change when using points alone or as a trigger.

Regards,

John

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