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Detroit Flathead 05-05-2012 11:56 PM

Flathead 8BA Wiring Help - Temporary Start Up

I'm in need of the expertise you guys have. Electrical is not my strong suit, and I've never done what I am trying to do. I've done some searches, but I haven't found what I need. I just want to start up my 8BA engine while it sits in the frame. Here's what I have: An 8BA bolted in the frame, attached to a Mercomatic. I have a newly rebuilt starter, the original 6V coil (with BAT and DIST terminals) and distributor, a 1.5 ohm ballast resistor, a 12V generator, and a 12V battery. Radiator is hooked up too. I'm in the process of doing a 6 volt to 12 volt conversion as I put the car together. I tried wiring this up today, temporarily to turn it over, and I had no luck, other than melting part of the battery post. Can someone spell it out for me? Tell me exactly how to wire this thing temporarily to run it for a few minutes? What wire starts where and goes where? Wire gauge? Feel free to draw a picture or explain it like I was 6 years old. For what it's worth, I plan on getting a 12V coil and Bubba distributor, but I haven't yet.

George/Maine 05-06-2012 05:26 AM

Re: Flathead 8BA Wiring Help - Temporary Start Up

First off you need a 12 volt coil and a resister.
This setup works for me.
Its a 12 volt coil for a 68 chevy pu and resister for same.
The yellow wire is power wire,thur resister,then to coil pos the neg you can,t see goes to dist.This coil fits holder thats why i us it.
Use neg grd and 12 volt.Yellow wire to pos by way of switch or clip for quick disconnect.get a selinode for starter.
Just run off battery no gen or alt.

Mike51Merc 05-06-2012 07:44 AM

Re: Flathead 8BA Wiring Help - Temporary Start Up

Hey Detroit, I see you come here, too.

Scott H 05-06-2012 08:14 AM

Re: Flathead 8BA Wiring Help - Temporary Start Up

Just for starting purposes while its sitting on the frame you won't need to worry about wiring the charging system. You WILL need the 12 volt coil.

You need power to the starter that you can interrupt, either with a switch or by just touching the connections together (a momentary pushbutton switch is preferred)

You need power to the coil that you can interrupt, again a switch is preferred so you can cut the power and stop the engine.

Are you going to have a negative ground along with your 12 volt conversion?

If so, from the battery use a thick cable from the negative post and attach the other end to a bolt on the engine. Run a thick cable from the positive to one side of your switch, and then continue it from the other side of your switch to the starter. When you flip the switch the starter should spin adn the starter should stop when you cut power at the switch.

For the coil, run a standard wire from the negative side of the battery to the GROUND side of the coil.
The run a standard wire from the positive side of the battery to a switch, from the other side of the switch to your resistor. From the other side of the resistor to the BATT side of the coil. Flipping the switch will give you the stepped-down voltage you want to the coil so the coil doesn't burn out.

rotorwrench 05-06-2012 10:57 AM

Re: Flathead 8BA Wiring Help - Temporary Start Up

The 6-volt coil will work with the 12-volt systems just fine as long as you use a ballast resistor and 1.5 Ohms should do OK. That will cut the voltage back to the 6-volt level and keep the amperage under control. All the other charging system stuff in not needed except to add a fan for cooling and keep your water pumps turning if you are goind to use a radiator cooling system. The polarity has to be reversed on the old coil for negative earth and you need to veryfy that the old coil is still functional. The "Dist" connection would become the "Bat" connection if you reverse polarity. With 12-volts you would only need 18 guage wire for hook up. 16-guage would be overkill. Coils made for 12-volt systems usually have enough internal resistance that they don't need a ballast. One can be used though but the ballast resistance could be less than .5 Ohm to be effective.

Most folks agree that extended running of an engine (especially a fresh rebuild) is not a good idea unless you have the capability to load it with a water brake or by turning something else to apply load. You can start at idle for a bit & check for leaks but thats about it. An engine really has to be loaded in order to break it in properly. I just use wires with aligator clips on them for hook up & disconnect. You can turn the starter with jumper cables just to get it running. I use direct reading oil pressure & temp guages along with a infrared temp gun to check for hot spots. Anything more elamorate than that is a waist of valuable time in my opinion. Now if you have an old saw mill and need to cut some lumber then that's different.

Kurt in NJ 05-06-2012 02:52 PM

Re: Flathead 8BA Wiring Help - Temporary Start Up

Because the trans has bushings it will need to have oil in it so it can pump it's own lubricating oil to the front pump bushing--and other internal parts.----it is easy to forget when you are just thinking about running the engine.

Running without coolant even for a short time is not good---I wouldn't run an engine without coolant any longer than I would run it without oil.

George/Maine 05-06-2012 03:48 PM

Re: Flathead 8BA Wiring Help - Temporary Start Up

Here is diagram that may help you.
This is with key start and run.
I would use a 12 volt coil and resister they only draw 2 amps.
Playing with the new computer.

Detroit Flathead 05-06-2012 05:31 PM

Re: Flathead 8BA Wiring Help - Temporary Start Up

Thanks guys, for your info. I'm going to go ahead and get the 12V coil, and a few other things to make this easier. I do plan on going to a negative ground with the 12 volt conversion.

40fordpu 05-07-2012 03:53 PM

Re: Flathead 8BA Wiring Help - Temporary Start Up

Good Descriptions

295W 02-04-2015 07:06 PM

Re: Flathead 8BA Wiring Help - Temporary Start Up

know I am posting to an old post but....
I have started my engine well turned it over using a 68 chevy coil but the parts store only had a generic resistor. The engine will not kick over with the wiring through the resistor but will with out it. I measure 2.9 volts or there about with the resistor and 10 or more with out.... of course the coil gets very hot when I do not use the resistor. Shouldn't a ballast resistor reduce voltage to 6 or 7 volts - ideas on where to get the correct one?? Thanks!

JSeery 02-04-2015 07:47 PM

Re: Flathead 8BA Wiring Help - Temporary Start Up

Should be around 1.5 ohms and supply somewhere around 6 to 7 volts to the coil. If you are using a starter solenoid with the connections on it the best set up is "S" to your start switch/ignition switch and "I" to the coil. This will put 12V to the coil during startup and cut off with the starter. The ignition post from your ignition switch should go to the ballast resister and the other side of the resister to the coil to power it at around 7v in the RUN position of the ignition. So in START you have 12v to the coil and when you release the key to RUN position you have 7v to the coil. I don't know about a source, most older Chryslers use them.

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

NAPA* Echlin* ICR11 (1.35 Ohms)
NAPA Echlin ICR23 (1.20 Ohms)
NAPA Echlin ICR34 (1.40 Ohms)
Lucas* 3BR (1.3 - 1.4 Ohms)
Mopar* DCC-4529795 (1.40 Ohms)
Accel* ACC-150250 (1.35 Ohms)
Standard* RU-4 (1.35 Ohms)
Standard RU-23 (1.20 ohms)
Standard RU-37 (1.40 Ohms)

JSeery 02-04-2015 07:58 PM

Re: Flathead 8BA Wiring Help - Temporary Start Up

2 Attachment(s)
A couple of diagrams.

295W 02-05-2015 09:13 PM

Re: Flathead 8BA Wiring Help - Temporary Start Up

Thanks everyone! The diagrams are great!! Do I have to use a solenoid I'm just getting this engine to fire and then maybe run a bit.....?

JSeery 02-05-2015 09:16 PM

Re: Flathead 8BA Wiring Help - Temporary Start Up

Nope, as long as you understand what your doing.

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