MSD conversion wiring

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nrubino

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Hi, im doing an MSD ignition in a 67 cuda.

Im adding a new after market distributor with MSD coil.

Do I unhook the big Resistor or leave it hooked up?

Im also going to a 1 wire alternator with built in regulator. what do I do with the wires from the old regulator and the extra alternator wires?

Thanks!

Nick
 
Actually the MSD should not matter. All the old ballast / ignition circuit does with an MSD is to trigger what amounts to an internal power relay / or maybe solid state switch.

The main power for the MSD now comes on the two "big" wires, red and black

READ your MSD stuff carefully. You don't want to leave the old radio condenser hooked to the coil, nor the tach. In fact the ONLY two wires you want hooked to the coil come from the MSD

The old alternator wiring, tape off or remove.
 
I thought the ballast resistor cuts down the 12v to like 8v or 6v to the coil that is why it got bypassed when useing the MSD.

67Dart273 said:
Actually the MSD should not matter. All the old ballast / ignition circuit does with an MSD is to trigger what amounts to an internal power relay / or maybe solid state switch.

The main power for the MSD now comes on the two "big" wires, red and black

READ your MSD stuff carefully. You don't want to leave the old radio condenser hooked to the coil, nor the tach. In fact the ONLY two wires you want hooked to the coil come from the MSD

The old alternator wiring, tape off or remove.
Click to expand...
 
That's right, but the thing is, the ballast is no longer a "high current" path. All the original ignition switching (key, bypass, ballast) is doing with an MSD is feeding the "small red" which is a switching wire. This is the same idea as turning on a relay, except it's probably just turning on a switch transistor.

Here's the thing, "Ohm's law." The voltage "coming out" of the low end of the ballast depends on the CURRENT going through it. If you measure coil+ voltage with the key on in a factory car, the coil will read a very low voltage, 4, 5, 8 volts, depending on the coil.

But if you open the points or disconnect the coil, that same point will measure "same as battery." That's because there is no longer current flow.

MSD "small red" trigger wire is going to be somewhere in the middle. I would love someone to measure the draw on that MSD trigger, but I don't run 'em and don't have one.
 
So let me get this straight i can hook up my ballast resistor back up so it looks stock? right now i have it unplugged and just hanging there because the MSd is installed.

67Dart273 said:
That's right, but the thing is, the ballast is no longer a "high current" path. All the original ignition switching (key, bypass, ballast) is doing with an MSD is feeding the "small red" which is a switching wire. This is the same idea as turning on a relay, except it's probably just turning on a switch transistor.

Here's the thing, "Ohm's law." The voltage "coming out" of the low end of the ballast depends on the CURRENT going through it. If you measure coil+ voltage with the key on in a factory car, the coil will read a very low voltage, 4, 5, 8 volts, depending on the coil.

But if you open the points or disconnect the coil, that same point will measure "same as battery." That's because there is no longer current flow.

MSD "small red" trigger wire is going to be somewhere in the middle. I would love someone to measure the draw on that MSD trigger, but I don't run 'em and don't have one.
Click to expand...
 
johnnycuda said:
So let me get this straight i can hook up my ballast resistor back up so it looks stock? right now i have it unplugged and just hanging there because the MSd is installed.
Click to expand...

I don't know why not, but I think the main reason to eliminate it is to get rid of, as Columbo would say, "just one more thing."

How are you gonna make it look stock with a Big Red Box in there, anyhow, LOL
 
I switched my 64 Polara 440 to a Mallory highfire box and coil and it never would charge the same. All the lights flickered all the time. The car was smoother at idle and did start quicker but we had to eliminate everything according to Mallorys tech line. I wouldn't use Mallory again as they were horrible on support. I hope your MSD works better!!
 
You can also take a piece of wire and solder it across the backside of your resistor. Looks factory from the front, removes the resistor from the circuit.
 
dans4door1970 said:
I switched my 64 Polara 440 to a Mallory highfire box and coil and it never would charge the same. All the lights flickered all the time. The car was smoother at idle and did start quicker but we had to eliminate everything according to Mallorys tech line. I wouldn't use Mallory again as they were horrible on support. I hope your MSD works better!!
Click to expand...

Your right about lousy Tech support @ Mallory. I use to run Hi-fire boxes but when I tried to get some help out of them it was non existent. MSD only now.
 
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