converted to 12v, what coil?

[52concord]

so i bought a 52 concord a couple days ago, its been converted to 12v and while i was checking out the engine i notice it had a 6v coil on it, is it alright to run a 6v coil on a 12v system? if not where can i get a 12v coil that you guys recommend?

[Plymouthy Adams]

only through a dropping resisitor..it must be installed in series with the coil..you can allow for a better start if you also run a 12V start (ign sw. start circuit) wire to the + side of the coil at the same time.. start on 12 run on 6..

[falconvan]

Just tell them you need a coil for a 1972 Chevy truck with a 350; that's a good universal coil. Also you will need a ballast resistor; early 70's Dodge truck should be the right one. You need the one with two terminals instead of four.

[Plymouthy Adams]

depending on your engine 4, 6 or 8 cylinder, your intended operation RPM and the actual internal resistance of the coil as to what dropping resistor you will need to ensure proper saturation of the coil windings to produce the correct spark without drawing too little current or more important, too much current..bit more to it than grab a coil, grab a resistor for performacne reasons but as a rolling turd on the highway with the flathead six..yeah.about any coil any resistor..

[52concord]

alright then i got the idea, now and im running a 218 with a three speed

[drillmastertommy]

I'm running a 1.5ohm Petronix flamethrower with a ballast resistor on my 218 3 speed and it runs great, starting has just got better after adding a Petronix ignitor electronic ignition.

[55 Fargo]

I know my 12 volt 55 Fargo truck starts so easy it is unbelievable. I have a 12 volt coil, stock ballast, and points, no solid state ignition. I can see adding the electronic ignition will make it start and run better.

Honestly Guys, this truck starts 9 times out of 10, as well as my 2005 Dodge Caravan, even after sitting for days...

[52concord]

And i got another question, is running the electric fuel pump positive wire connected to the positive side of the coil alright?

[ptwothree]

I'm running a 1.5ohm Petronix flamethrower with a ballast resistor on my 218 3 speed and it runs great, starting has just got better after adding a Petronix ignitor electronic ignition.

What part pertronix part # and what year distrib are you using?

[drillmastertommy]

My distributor is an Autolite IAT-4101 Part No 1479589 on a 53 Plymouth engine and the Pertronix ignitor part number is 1362. Apparently it's an industrial application but readily available. Coil is a standard 1.5 ohm Pertronix flamethrower.

All of the stuff was real easy to install although in the Ignitor instructions it says "if you have to make any modifications,you have the wrong part". A call to Pertronix later I find I have to remove 2 rivets from the dist plate and the contact stand. A good opportunity to clean the internals, half hour later, a cup of tea and it was in. No gapping to do and no more points to replace.

[Don Coatney]

Honestly Guys, this truck starts 9 times out of 10, as well as my 2005 Dodge Caravan, even after sitting for days...

I would not be very happy if my engine failed to start 10% of the time.

And i got another question, is running the electric fuel pump positive wire connected to the positive side of the coil alright?

I suggest you connect the electric fuel pump to the ignition switch not the coil and I suggest you install an in-line fuse. Is there a problem with your mechanical fuel pump?

[Plymouthy Adams]

a good idea in routing the wiring to the fuel pump is to use a relay and keep as much current as you can from flowing through the ignition switch..these switch units are very well made as most are still original but can be overloaded..they were not designed with a whole lot of current in mind.

[Don Coatney]

a good idea in routing the wiring to the fuel pump is to use a relay and keep as much current as you can from flowing through the ignition switch..these switch units are very well made as most are still original but can be overloaded..they were not designed with a whole lot of current in mind.

You are correct and I should have mentioned that.

[greg g]

Most stndard coils are designed to work in the 6 to 8 volt range. So if the coil is sotck and the vehicle has been changed to 12 V a resistor is needed to drop the 12V to that range, Mopar used a balast resistor, typically a ceramic piece with a resistor through which the 12 v in was reduced to 8 v out. Some brands used a restor wire from the ign switch to the coil, and some used an internally resisted coil which did the job internally of dropping the 12v in to the working range.

So if your coil is the stock oneand the vehicle has been changed to 12v then it needs to have some form of voltage drop between the ign switch and coil. Or it may have had an internally resisted coil installed. If so it should be clearly marked on the outside of the coil.

The other item that needs to be considered is the current path through the coil. From the factory your 6V system was wired Ign to neg terminal, positive term to points. When switched to 12 V most folks would also go neg ground. In that case the coil terminals should be wired to reflect the gounding, as in ign to pos, neg to points.

It will run either way but may show some break up or loss of power and or high speed ignition miss in the upper rpm range. when incorrect it can also negatively impact the service life of the points.

So if you or some one else has changed the cars electrical voltage or gorunding it is good to recheck all these connections.

You could certainly power a relay for an electric fuel pump using the ignition side of the coil connection. But I would not run the pump direct from that terminal. On my studebaker truck the pump is run through a fused circuit though a toggle switch powered from the ign terminal of the ignition switch.

[55 Fargo]

I would not be very happy if my engine failed to start 10% of the time.

In my case:rolleyes:, the 10th time, means a few more cranks.......

[52concord]

alright then so if i want to get a internally resisted coil? whats the part number or where can i get it? so i found that this coil has a internal resistor, will i be fine with this? http://www.autozone.com/autozone/parts/_/N-9n80r?itemIdentifier=123109_0_0_

Edited April 6, 2012 by 52concord

[greg g]

Unless your coil is know to be bad why not just wire in a ballast resistor? they are still less than 10 bucks.

[52concord]

i just got the car, so i decide to do a full tune up and replace the coil while im at it.

[greg g]

I would still choose a standard coil and an external resistor, but the choice is yours. I can not give you any information reguarding the coil you posted would be proper for your application.

[deathbound]

a good idea in routing the wiring to the fuel pump is to use a relay and keep as much current as you can from flowing through the ignition switch..these switch units are very well made as most are still original but can be overloaded..they were not designed with a whole lot of current in mind.

Sorry for getting off topic, can you post a step by step on how this would be wired (& what type of relay to use), also with a toggle switch in-line.....for 12V neg ground. Thanks

[greg g]

three post self grounding relay, single throw toggle, 14 gauge stranded wire for 12V, 12 gauge for 6V power off Ign post not acc or start on ign seitch.

[martybose]

While I was troubleshooting my engine miss (which ultimately turned out to be a hairball of some sort in a carb jet) I originally thought that the problem was electrical. So I built a panel that is mounted under the dash that has a pair of mini fuse panels, each fed by a small 70 amp relay. Now everything electrical in the car is fed from there, and all the ignition switch does is activate the two relays.

Marty