Mallory ignition questions, Partial success! Options

[VaccaRabite]

My carbed 2056 uses a Mallory Unilite ignition. All summer long I have been fighting intermitant misses leading to the motor dieing at idle. After dicking with the carbs and adding fresh spark plugs, I am now moving to ignition.

So here is how my system is set up.

Bosch blue coil.
Mallory Unilite ignition.
The ignition is behind a resistor block.
MSD spiral wound plug wires.
NKG b5es plugs pregapped (one heat range hotter then stock as suggested in the resent spark plug thread) .

My tach is not dancing when I have a miss. The idle indicated drops as expected, no drama. So I don't think that the coil is grounding out or arcing.

As I understand the Mallory dizzy, it either works or it does not work, and there is not a lot of in-between.

My primary suspects are the plug wires. I am using the MSD spiral wound wires suggested for use with the Mallory, and I have only been using them this season.

Since you are not supposed to use the regular plug wires with a Mallory (as they can somehow cause the optical unit to burn out) buying replacement wires on a hunch is kinda expensive. Am I chasing my tail with this?

Also, I am using the stock gap. I think I am supposed to be able to use a wider gap with the Mallory, which will give better ignition. What kind of gap should I be shooting for? If it does turn out to be the plug wires as the problem area, should I go back to the stock heat range plugs, or stay with the hotter ranged plugs?

Oh, and for the "go back to FI" crowd, my motor is using a cam that would cause D Jet to commit suicide. In this case, it is not an option.

Zach

[VaccaRabite]

Idle is set at 1100 RPM. I am using the grey springs for the Mallory which is I think either 12 or 16 advance at idle, but I have never timed for idle. I set timing at 28 degrees full advance, which I hit by 3K rpm.

Zach

[ChrisFoley]

Idle is set at 1100 RPM. I am using the grey springs for the Mallory which is I think either 12 or 16 advance at idle, but I have never timed for idle. I set timing at 28 degrees full advance, which I hit by 3K rpm.

Zach

The mallory distributor springs don't govern degrees of advance, only the shape of the advance curve.
Amount of centrifugal advance is controlled by re-clocking the advance plate, using a plastic gauge provided in their spring kits.
We also bend the spring tabs to raise the rpm where advance begins.
You should have 16 degrees of centrifugal advance, starting at 12 degrees initial. At 1100 rpm idle I wouldn't be surprised if you are already seeing some centrifugal advance.

[VaccaRabite]

The mallory distributor springs don't govern degrees of advance, only the shape of the advance curve.
Amount of centrifugal advance is controlled by re-clocking the advance plate, using a plastic gauge provided in their spring kits.
We also bend the spring tabs to raise the rpm where advance begins.
You should have 16 degrees of centrifugal advance, starting at 12 degrees initial. At 1100 rpm idle I wouldn't be surprised if you are already seeing some centrifugal advance.

I got my Mallory when I got the engine. I had always wondered what the little ring of red plastic "keys" were.

I had to replace the optical sensor last year. Would that install have caused my advance plate to shift? I followed the instructions on the optical reinstall and don't remember needing to reset anything. But that does not mean I was supposed to.

This issue is infuriating. When the car is running, its running like a bat out of hell, very strong. but when it starts missing, driving the car at lower RPMs can become very challenging. Part of the reason that I have my ilde set high was to give me some lead time before the engine would stall out during a missfire event.

Zach

[ChrisFoley]

I had to replace the optical sensor last year. Would that install have caused my advance plate to shift? I followed the instructions on the optical reinstall and don't remember needing to reset anything. But that does not mean I was supposed to.

Replacing the timing unit shouldn't affect advance settings, but you do need the optical unit out in order to set the advance.
You have to loosen the two Torx screws to move the plate, then insert the 16 degree key in the opening, close the opening against the key and re-tighten the screws. Bending the spring tabs to tighten the springs is just as important as setting the max advance.
Once you determine exactly which cylinder is dropping out you'll be able to diagnose the problem.
If you don't have a pyrometer to check which exhaust pipe is cold, you can pull one plug wire at a time from the distributor cap (using insulated pliers). The one that doesn't affect idle is connected to the bad cylinder.