12 volt coil vs resistor

I have been viewing the many posts on the subject, but I am still not entirely clear, and would like some advise on my problem. My 6 volt charging system on my side mound distributor 8n finally gave up the ghost so I figured it was a good time to convert to a 1 wire 12 volt system.
Everything went well until no spark for starting. The resistor that came with my kit (which was meant for a 6 volt coil ) cut the voltage too low for my coil to produce spark. I bypassed the resistor and the tractor started and ran perfect. I understood this should not be good for the coil, so I started reading and investigating.
I found I had an ignition coil # 27310, which I believe is a 12 volt external resister coil. So [u:3e5844df71]it looks like I have been running a 12 volt coil off of my 6 volt system for years[/u:3e5844df71] with no resistor and no problem.
My question is, can[u:3e5844df71] I safely run this 27310 12 volt coil with no resistor or will I cook it.[/u:3e5844df71] Understand the resister that came with my kit is for a 6 volt coil and will not work.

On another note, my original ballasted resister is still there, but not used in my new 12V wiring or previous 6V wiring. Should I give it a try and see if that works for me.
Sorry for the long post but I wanted to provide enough info. Great forum!

BEST test would be to measure primary current flow. Typically, 3 to 4 Amps is probably OK, much less and spark will be weak, as you approach and pass 4 Amps, it's tougher and tougher on coils and points.

Thanks, but I have no way to measure amps

NAPA 12v coil no resistor, part number
IC14SB is 3.25 ohms and will work perfectly.
75 Tips

Why does that surprize you, using a 12-to-6 volt converting resistor ...and... a real 12-volt round can coil, you have WEAK sparkies??? You are trying to run a 12-volt coil on 6-volts. (by using a 12-to-6 volt convering resistor) Remember, ONLY the 4-nipple squarecan coil requires the infamous ballast resistor. You have a 5-nipple roundcan coil, do as Bruce suggests, use a REAL 12-volt round can coil, NO RESISTOR NEEDED. Understand???........the amazed Dell and sparkie-meister

Perfect, I will pick one up tomorrow. Thanks

You're welcome. Glad to help.
75 Tips

The only "surprise", here was finding out a previous owner had replaced the original 6V coil with a 12V coil (#27310) on a 6V system.

Welcome to the forum.
A 12V coil "for use with an external resistor" really isn't a 12V
coil. A true 12V coil is wound differently and doesn't need an
external resistor. Like the one Bruce recommended.
I use a 12V coil and lose the resistor. Less connections to corrode.

Interesting too that your tractor has the "original" ballast resistor.
They were only used with the front mount distributors.
Maybe an engine or dash swap at some point in time.
These great machines have been through a lot!

Interesting point you make about the ballast resister, which was there, but not being used on my 6V set up. You are so correct when you say these machines were through a
lot, It sure makes one wonder about the history of the equipment and the people that used them over the years. Have to wonder how many a person struggled with running
problems with no one to help them out, like you can get today, on forums like this with so many helpful and knowledgeable people. Thanks to all. Bill

Peak current is;
I=V/R
I=12/3.25=3.692 (A)
While alt is charging;
I=13.8/3.25=4.246 (A)
The average current is less due to dwell time.
The time spent with open points is the dead time.
So, that is a start to understanding the current.
If you were to put an analog current meter that has low impedance in series with ign switch line to coil, then you would be reading the "average" current.
Greg

Vicky.........shure you do. There's an AMP meter on the dash of yer 8N. Gotta admit 3-amps onna 30-amp meter is probably just 1-needle wide. .........The amazed Dell and electronic engineer (ret)