The Stovebolt Site Forums The Shop Area The Electrical Bay Coil from 6v to 12v

Someone has previously, done a 6v to 12v conversion on my truck. The current setup has a coil marked "for use with external resistor" with of course an external resistor. The coil on there appears to be leaking some oil. I have an MSD blaster 2 that I would like to use to replace the current coil. If I do use the MSD coil, do I still need the external resistor?

Thanks,
BH

I don't know what you're working on (always good to let folks know so they can give better advise), but generally speaking, a 12v system needs 12v at Start, and 8v (or so) to Run. When you turn your key (if you have one) to Start, 12v goes to the coil. When you let off your key (if you have one) and it goes to Run, 12v goes to the resistor, and from there to the coil.
Now wait for someone more knowledgeable than I am to correct me and good luck with your truck!

BH,

You might want to post the model number of your MSD coil?
And/or the brand/model of your ignition system?

As per the notes in this listing?

I will have to check the coil number later. All I remember is that it is a MSD Blaster 2. What information do I need to get for the ignition system? I should probably know, but I don't. The truck is a 1955.1 Chevy 3100, 235ci engine.

If your MSD coil has a internal resister then no. Read our tech tip on converting to 12 volts for some good info.

Note: The Blaster 2 does not have an internal resistor so you will need a Ballast Resistor to use it.

Thanks, that's what I figured, but wanted to hear form others.

BigHog, just a word of advice about posting. Always start your post with what your working on, ie; I’m working on a ‘55 1st with stock engine and drivetrain. My question is ...............? That will help us help you. It’s hard to remember to do, believe me I know, but you will get the hang of it. Please read post #1 in General Truck Talk if you haven’t already. Lots of good info there about the site.

Will do.

BH

I just bought a 6V coil that is marked "No external resistor required". So, I did not use the (probably bad) existing resistor.

Verified my MSD coil is an 8202, no additional numbers or letters on it.

Per their description:
"Blaster Ignition or MSD 5, 6, and 7 Series (ballast resistor required for points)"

Thank you, Victor

6 volt coil/ignition does not require & must not be used with a resistor.

Good copy. Thanks!

Stock up on points- - - -you're going to need about one set a week with that coil.
Jerry

Why is that?

Bighog i have a small collection of 12v coils, likely with the internal resistor if you want or need. You can have and try. I have found, the less you modify and less you need to (also) modify.
Either way throw points and condenser in your glove box just in case.

Hambone, I appreciate the offer. I was curious as to why my new coil would go through points faster. Keeping an extra set of points in the glovebox is sound advice an inexpensive insurance.

BH

All enhanced secondary voltage coils do so by flowing more current through the primary winding to develop a stronger magnetic field. Mechanical points can tolerate a maximum current flow of maybe 5 amps. That "Blaster" coil is capable of flowing around 15 amps in the primary circuit. It's intended to be used with a solid state ignition module that does not have points. The points will look like an arc welder if they're allowed to flow that much current. If you use a big enough ballast resistor to limit the primary current to an acceptable amperage, there's no reason not to use a plain old original equipment coil with the correct resistor for that application.
Jerry

Thanks, I have a ballast resistor inline, I thought that would be enough. I just had the MSD laying around, so figured Id use it.

Check the voltage at the coil + terminal with the engine running. If it's more than around 9 to 9.5 volts, you'll need more resistance than the OEM ballast can provide. I'm not really sure the MSD coil will work properly with voltage that low.
Jerry

Copy, will do. Like I said, I had it available. It appears that a regular replacement coil is less than $14. I will probably just get one.

BH

If you do decide to replace it, try to find a New Old Stock (NOS) Delco/AC coil. The Chinese ones are junk.🛠

copy that, its probably the Chinese ones that are less than $14

There are still plenty of OEM Delco coils on Ebay at reasonable prices. When it comes to GM ignition parts, there are two choices- - - -"Delco" and "wrong"!
Jerry

I will check my stock of used, dirty, coils free to good home. I will ship as well since my favorite brewery is in your area and it gives me a better excuse ( if ever needed) to strap into my 62.