New Member and Voltage Reducing Resistor

[delta31]

Hi
I'm a new member to this forum just got a Fire Dept M37.
The plan is to get it running and then decide what to do for restoration.
I have a few questions for this group.

1) NAPA sells a voltage reducing resistor for a 6 v coil to be used with 12 volts. Could this be used to reduce 24 volts so a 12 volt ignition coil could be used
for short term? Would I need two of these?

2) The tang of the civilian autolite distributor had been modified to be offset to fit the military oil pump. is this something that was commonly done?

The distributor shaft appears to be straight within .004
The starter and generator are 24 volt and a lot of original wire is gone.

Long term plan if we can reduce the voltage rather than come off one of the batteries would be a new oil pump and rebuild distributor
unless its possible to rebuild it my self.

Appreciate any advice and answers.
Thanks

[Cal_Gary]

Hello Delta and welcome!
Thanks for saving another one. I merged your two posts into one and approved it.
I don't know about your resistor question but the forum folks will surely weigh in if they know!
Trimming the distributor tang isn't a common mod-most go with the matching civvy oil pump to mate up to the civvy distributor. If you have the military distributor the tang should be off-set (a sure way to tell if you've got a mismatch is that the civvy distributor will wiggle in motion if paired with the military oil pump.

Feel free to do some site searches above-right, as many of your forthcoming questions will have already been discussed so that will save you some time.
Finally, please add your location to your profile so we know where to route you for vendors and such-your current State of residence is sufficient.
Thanks!
Gary

[sturmtyger380]

Welcome! We always like to see pictures!

Do you know what kind of resistors are in the unit?

Normally the circuit has the voltage going in, then into the first 10K ohm resistor with a shunt off for the halved voltage. The other half of the voltage goes through the other 10k ohm resistor to ground.

But yes, it should cut 24 volts in half to 12 volts just like going to 6 volts.

[ashyers]

delta31,
It is possible to knock down the voltage from 24v to work with another coil. A friend of mine has a truck that is 24v except for the coil/distributor, it has a giant ceramic resistor that reduces the voltage for the coil. There are also a variety of voltage converters out there that may do the trick. I wouldn't modify the oil pump drive tang on the distributor shaft. If that sucker shears off your motor is toast.

Andy

[m-37Bruce]

Hey Delta,
Welcome to the OD vehicle owners club!
Is your resistor a ceramic bar with wires on either end?

[delta31]

The resistor I bought NAPA ECHLIN VT6187 is kind of round ceramic with town tabs and one is labeled batt. Also there is a 7/16 mounting bolt. I wonder if this is a ground.
Thanks

[PoW]

A resistor to drop voltage is dependent on how much drop needed, and the current thru the resistor.

It will be unsatisfactory if any of those parameters is off.

One needs to calculate the needed resistance via Ohm's law, to get the correct resistance and Wattage to handle the demand.

To make this a bit more difficult, the resistor will only do right for a fixed demand.

BTW, voltage drop resistors for automotive use are designed to cover limited usability.

Usually, they are under 50 Ohms, at least 50 Watts dissipation, and there are NO grounds necessary with them.

You would be better off with a DC to DC converter module (eBay), capable to handle the expected load. These can easily handle variable loads without causing trouble.

PoW