Ignition primary for 12v conversion
 

I am converting my ‘36 to 12v neg ground as part of an engine swap ( now a ‘48 59 AB). The engine came with a 12v Powermaster one wire alternator and a Powermaster starter. The pic attached is the resistor unit found under the dash of the original ‘36 6v system. I presume this is a voltage reducer for the ‘36 coil, not really sure. I now have the ‘48 distributor and plan to use a ‘60’s vintage 12v gm coil I had on the shelf. What voltage does the coil need while running? And what value ballast resistor will achieve that? Also, with the stock ‘48 points distributor, should I include a full voltage resistor bypass in the start circuit, or is this unnecessary?
Thank you,
Pat

Re: Ignition primary for 12v conversion
 

Re: Ignition primary for 12v conversion
 

Use a coil with 3.5 ohms and forget the resistor.

Re: Ignition primary for 12v conversion
 

Use the Bosch blue coil Bubba always says, no resistor needed

Re: Ignition primary for 12v conversion
 

3rd for Bosch Blue but I painted mine as blue just isn't my color.

Re: Ignition primary for 12v conversion
 

There not a lot written about the resistor in your hand from Ford , It has been discused
here from time to time .From what i can tell
it is to boost voltage for starting and reduce running voltage because the 6 volt generator can run up wards of 12/14 volts .preserving point life was the aim of the game ,I often see them on cars with a by pass switch but in the day over here the penny across the bolts did the trick as they heat up resistance goes up . in the sixties a lot of the battery cables got switched to small 12 volt cables coupled with corrosion in wiring connections the starter will pull much needed voltage from the coil ,result a non starter .

Re: Ignition primary for 12v conversion
 

I discovered I have a helmet type distributor, not a later style. It appears new/rebuilt and I will presume that H&H set it up on a machine and will use as-is to get the motor running. It has an adaptor cap in place of the stock coil to run an external coil wire.

So the recommendation is to run a 3 ohm coil, the Bosch blue VW being one. The PerTronix 40611 is also listed as a 3 ohm coil and is priced a bit better - not sure where it's made. Can anyone confirm that is also a good alternative coil?

Thank you!

Re: Ignition primary for 12v conversion
 

why ask for advice and then not take it? several people including me have experience with the "blue coil" and are extremely satisfied with the results and heartily recommend them

Re: Ignition primary for 12v conversion
 

No disrespect intended. A quick online search for "Bosch blue 12v coil" led me to many brands and alternatives, including Bosch and Bosch lookalikes clearly not from Germany, ranging in price from $35 to $300. Without a Bosch part number, I'm sort of guessing either way. Thank you, I'll search for more info on Bosch 3 ohm.

Re: Ignition primary for 12v conversion
 

I understand your concern. Many here use the Bosch coil with success. There was a period that Amazon had them for about $25. I have heard complaints on the Pertronix coils. I think some of those might have been self inflicted because of the requirements of different Pertronix ignitors. I have used several Pertronix ignitors and coils with success, just follow directions. You don't have to use a 3 or 3.5 ohm coil. A 1.5 to 1.8 ohm ballast resister will work fine with a 1.5 ohm coil. Then, if you have voltage related hot start issues you can bypass the ballast resistor during the cranking time.

Re: Ignition primary for 12v conversion
 

I 2nd the 1.5 with a Ballast ,I use it ,

Re: Ignition primary for 12v conversion
 

great info everyone, Thank you!

Re: Ignition primary for 12v conversion
 

If you are going to run the helmet dizzy, you could send an original Ford coil down to skip haney in fl. and have it rewired to 12 volts. It would then need a ballast resistor, but would look proper and I've read many posts here on the barn of those modern coil conversion plates failing for some reason or another.