12 Volt Flathead - temporary wiring advice needed

I'd like to temporarily wire up my 8BA Flathead so I can run it for a while. It's sitting in the chassis, and I'll be hooking up the radiator. Is there anything specific to my setup that I need to know? It's got a 12 volt generator and a stock 6 volt coil and distributor. I also have a 1.5 ohm ballast resistor to drop the voltage going through the coil. This engine ran before I bought it, but it's been a few years. The pan has been cleaned out and fresh 15W40 Rotella has been added. I've done a few searches and found some general wiring information, but since I have not done this before, any and all advice is appreciated. If you have a wiring diagram for my setup, that would be great. Any instructions or pictures?

 

The 1.5 ohm is ok,
but you will not be able to use the 6 volt coil.
You should get a 12 volt coil.

 

I had been told the 6 volt coil would work, and the 1.5 ohm would help. For the sake of running it, I could put the 6 volt generator back on it, but I'd rather use the 12 volt.

I do plan on upgrading to a Bubba's Chevy conversion distributor and 12 volt coil, but I haven't yet.

 

The resistor drops the voltage for the coil and it should be fine. I assume you are not using the generator to actually charge the battery, just as completing the belt loop for the water pumps? If so it does not matter what 6V or 12V generator you use. The engine will run for quite a while on a good fully charged battery. Then all you need is to hook up wiring for starter and ignition.

 

I used one of Bubba's electronic dist. on my 8BA and it works great! Didn't care for the late model Chevy cap thing (looked out of place to me maybe?) so he made up one from an old Mallory dual point dist. using the smaller cap design.

 

38Chevy,
Good point... I don't even need to run power to the generator if it will run off the battery for a while.

 

If a stock six volt starter is in good shape, it will run on 12 volts for years without trouble.

 

Yep, the starter is like new. It was rebuilt.

 

Do I need a starter solenoid to start the Flathead?

 

If you plan on running it permanently on 12 volts, I'd suggest you get a 12 volt coil. Considering they're pretty cheap, there's no reason not to. Although the resistor will drop the 12 volts, if the 6V coil is designed to run with a resistor, it actually runs on less than 6 volts and your 12 volt system will never drop it enough.

To run temporarily, just run it off the battery, with one lead to the block and the other to the coil input. I didn't mention polarity, because you can do it either way. Just make sure the coil is wired in the right direction. For negative ground, the negative side of the coil goes to the distributor, for positive ground, the opposite. The battery lead goes to the other coil terminal. Use alligator clips for the battery connections so you can shut it off by unclipping the wire.

You can start it without a solenoid by using jumper cables to the block and the terminal lug on the starter motor.

 

12v coils are inexpensive and the comment about voltage drop is correct. I've run cars with 12v conversions for a short time using the 6v coil, but not for long. They get REALLY hot, and if they split, you could get burned quite badly by hot oil if you're standing nearby. And...it's an icky mess to clean up. Make the change now, and save yourself some trouble down the road.

dj

 

Thanks for the help, guys.

Mike51Merc, that description helps a lot.

I will be getting a 12V coil and Bubbas distributor, I just haven't yet. I probably should pull the trigger now and get them. I just want to start up this engine before I put the body back on the chassis.

 

My coil has two connections... one labeled "BAT", the other labeled "DIST". Since it is using the 6V coil, should I assume that the DIST is the positive side?

 

I think I tried what you described, and I was not successful. I'm sure once I do this correctly it will seem quite easy, but at the moment, I'm doing something wrong.

 

BATT and DIST have different meanings depending on the coil design. If it is a 6V positive ground (original to your Flathead), then the BATT is battery negative and the DIST is the "+" side. At this point, the coil you have is a mystery.

In any event, it WILL run either way, so if your engine isn't starting then focus on other issues. A backwards coil will still fire, just not as well.

 

Confirm solid grounds. Took 2 days after work to diag a no crank no start.... It was a loose ground connection.

 

It should be a stock 6V coil.