37 coupe V8 running rough after a 6 to 12 volt and pos to neg ground conversion

[crandalls6]

Hi I have a 37 coupe V8 that was running fine on 6v. I put a 12 volt battery in, changed the cables to neg ground, put in an alternator not hooked up yet--, changed to a 12 volt coil, I ran a wire from the pos battery to the pos side of the coil to test start. it acts like it is running on just a few cylinders, it will sputter for 30 sec and die. Do I need a ballast resistor? ...not sure why it isn't running like before. I'm upgrading this so I can put in better lighting, stereo, electric radiator fan... Thanks for any help... Crandall

[Tom Morookian]

Points and condenser are happy on 6 volts and probably unhappy getting 12.

toasted condenser and pitted points oops. Resistor!

Some coils have a built in resistor, sme don't Check instructions.

[Capt Kirk]

The coil instructions will say whether or not you need a ballast resistor. I don't think points care what voltage things are but they do care about a functioning condenser. I'm not sure if a condenser cares about voltage...someone else will chime in on this issue. If you fried the condenser then that may be your problem. Take a look in your distributor and await responses from those who know.

[crandalls6]

I replaced the condenser, points look fine... but still runs terrible, I'll put in a ballast now and let you know.

[40cpe]

You want about 3.5 ohm total resistance of the coil and the resistor. Measure across the + and - terminals on the coil with the meter and add a resistor to make up the difference.

[drolston]

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If you went to a coil that puts out 40,000 volts and have old or cheap ignition cables, you could be getting cross firing or shorting within the wire looms. Running without the proper resistance in the coil primary would further aggravate that issue.

[crandalls6]

ohms show 1.9 on the coil

[crandalls6]

The ignition wires are cloth, I'm wondering if it is bleeding those wires

[Frank Miller]

If you replaced the condenser the new one may be bad.

[flatheadmurre]

1.9 ohm tells us it´s not a stock non ballast coil.
So get a non ballast stock coil...or find the ballast resistor for that coil.

[JSeery]

If you are adding a ballast resistor it needs to be in the 1.1 to 1.6 ohm range. However, the ballast resistor is more of a long term thing and probably not the cause of the immediate problem.

Here’s some commonly available automobile ballasts available from NAPA:
•#ICR23 – 1.20 ohms
•#ICR11 – 1.35 ohms
•#ICR34 – 1.40 ohms
•#ICR37 – 1.60 ohms
•#ICR35 – 1.80 ohms
•#ICR13 – 1.82 ohms

[crandalls6]

I picked up a NAPA ICR23 1.20 resistance bringing my coil to 3.2 --- I also took the wires out of the metal tubes-- it still runs very rough backfiring a bit. won't stay running. noticed the ballast gets very hot, probably normal due to it's cased in ceramic . I appreciate all the help. I will get another ballast to get it to 3.5.... Any thoughts on the 932-41 Ford Flathead 3 Bolt Electronic Distributor "ready-to-run" unit that does not require a control box?

[flatheadmurre]

If it quits after just a short period of time there must be some other issues...
Running a coil to hot for a while shouldn´t make it sputter and die.
Either coil/points/capacitor is bad... or you have fuel issues.
I would start checking that you have enough fuel before changing to electronic ignition.

[crandalls6]

I will check the fuel

[Capt Kirk]

Firing order?

[crandalls6]

the fuel is not the problem, fuel bowl is full, and it is pumping fuel fine, it is mis-firing-- wires are solid core copper and cloth, I get shocked by just putting my finger close to the wire. will change the wires

[crandalls6]

UPDATE.... it is alive... The new condenser was bad. I borrowed one off my Subaru 360 Truck, and it started right up.. Also the cloth wires were occasionally sparking in the metal tubes so I replaced them with solid core 7mm.
Few notes if you are doing a conversion from six to twelve. 1. Use a single wire alternator.. one wire goes directly to the battery ---That's it--- it eliminates many wires.... 2. Starter will still turn correctly when you switch to negative ground 3. I was going to go to electronic ignition, but stayed with the stock 2 cap distributor... I lucked out because it had a blue Bubba's sticker on it. Thanks for all the advice. I really appreciate it. Tom

[flatheadmurre]

Good hearing you got it up and running.
Routing the cable directly from alternator to battery isn´t the way you should do it if you want your amp meter to work as it is intended to.
Connect it to the "fuseblock" under the dash instead.