Building a 12 volt starter

[Ed Pitts]

Last year Ronnie posted the following information on how to build a 12 volt starter. Here are some pics of the two starters: 6 volt for my 36 and a 12 volt from a 60's 390 cu. in. Ford. The case, back plate and the armature all have the same dimensions for both, so it will be a simple switch described below to convert my 6 volt starter to a 12 volt. The 12 volt case has red inside it.
Thanks Ronnie. Ed

"Found this info years ago

BUILDING A 12-VOLT STARTER
For all you with flatheads , here is how to build a 12-volt starter.

Take your flathead starter apart. Keep the long through-bolts and end plate with the armature and bendix. This would be a
good time to turn the armature. Never under-cut the copper bars or armature. Use the starter from 332, 352, 360, 390 or 406 c.i. Ford FE engines as the conversion starter. Disassemble the FE starter. Keep the end plate with brushes and case with field coils. Check the bushing in the end plate and replace if necessary. I have checked the wire size and number of windings on the FE and flathead armatures and they are the same.

This is also a good time to install new brushes. Install the flathead armature into the FE case. Install the FE end plate with brushes. Put long through-bolts in starter.

You now have a flathead starter capable of cranking an engine of 300 to 400 c.i. up to 11 to 1 compression ratio. The finished starter looks like the flathead starter and you did it yourself.

For the diehards who want the original 6-volt system: when rebuilding the flathead starter, use a lathe to turn twenty thousandth (.020” )off the steel part of the armature. This will allow the starter to spin faster.


Ronnie "

[richard crow]

hi ed the 6v starter in the photo is not a 36 it,s a later year proulby a 47 48 the front plate on the 36 is thicker ford in later years lenthed the field housing so they made the front plate thiner so to do conv. you have to use a later 6v starter front plate.

[Ed Pitts]

Richard, yes that is what I discovered. I had 4 starters, two of which had the 5 1/2 inch case and two with the 6 inch case. The 12 volt cases are 6 inches, so have to use the corresponding armature with the thiner front plate. This particular starter was on my 36 when I bought it.

[Junknshit]

Same size wire and same number of windings, same armature, I guess I don't understand what you are changing here. Other than replacing a bushing and brushes and cleaning up the comutator.

When you double the voltage, (6 to 12) you cut the amperage in half, so if you do the same (brushes, bushing etc) to your starter you have a starter which will do the same thing. Turn the engine over faster and last longer.

When you are changing to 12 volt, you can also run your stock generator. Clean it up, new brushes and bushings/bearings and run it. What is that seperate little box that your generator is wired to? AHA, it's a voltage regulator isn't it? Change to a 12 volt regulator and go with it. Don't believe it? Take your generator to any good rebuilder and ask him to check how much voltage it will put out. Most of them will put out at least 13.5 volts and a lot will put out about 15.

I also have a heater out of a 53 F-100 in another vehicle (69 Suburban) as a rear heater. It has a two wire motor in it, and has been in the 12 volt vehicle for over 15 years.

[denson1932]

John, when you double the voltage to 12V from 6V on a stock flathead starter, it then doubles the amperage, thereby the power (watts) drawn out of the battery and the power dissapated by the starter is 4 TIMES as much. If your flathead is a quick starting engine you can probally get away with it for some time.
Yes a 6V generator will charge to 13V but the field coils are designed to work on 6V and again with 12V they are dissapating 4X the power as when on 6V. If you had a voltage regulator instead of a cut-out it would help because it would just feed the generator field coils enough current to obtain the needed charge current for the battery instead of max field current.

[BCCHOPIT]

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I have been saving parts to make a 12v starter for my banger. But I have been running 12 volt on a 6 volt starter for 4 years now and it has not blown up yet.

[Junknshit]

When you double voltage you cut amperage requirement in half, not double it. That is the reason newer cars (12V.) can use smaller guage (larger numbered) wires to perform the same functions.

That is why I said voltage regulator and didn't say cutout.

If the windings have the same size wire and the same number of wraps, what have you changed?

[Bob C]

"I guess I don't understand what you are changing here. Other than replacing a bushing and brushes and cleaning up the comutator."

He changed the field coils.

Bob

[Junknshit]

I'm not trying to argue with anyone here, I'm always open to learning, I just need to know why. The starter and gen. things were explained to me back in late 50s by rebuilder, and I have done it since then, no failures. The motor thing, I just tried it, had nothing to lose, and it has worked quite a few times over the years.

[denson1932]

Well John if i read the instructions correctly you end up with the later starter's case with the 12V field coils. So now we have a starter for the flathead but with the correct voltage field coils.
Newer starters draw 1/2 as much current as old 6V starters because the 12V field is wound with twice as many turns of smaller wire. Most of the current probally goes thru the field since it is always energized when starting, wheras the communtator distributes the armature current for brief bursts to each pole winding. Of course if the starter is stalled then the armature is suspectable to MELT the soldered connections.

[Ed Pitts]

You are correct sir. Here is the completed conversion. The 6 volt armature fits the 12 volt case perfectly and the test with 12 volts was good. No worries now about breaking the starter drive spring, bolt or knocking the ring gear loose. The only thing I had to do was enlarge the holes in the end plate to 5/16 for the starter bolts.

[2935ford]

This is good to know info here, thanks.
I have run a 6v starter on a built 8BA with a 12v system for more than 7 years.
It takes less than a sec to fire the motor and has never failed me. Everyone is amazed at how fast it starts.

[Seth Swoboda]

Not trying to diminsih your idea, but you can run a 6v starter on 12 volts with no problems, just saves a lot of time and work. Good work though, nontheless.

[V8 Bob]

Originally Posted by Seth Swoboda

Not trying to diminsih your idea, but you can run a 6v starter on 12 volts with no problems, just saves a lot of time and work. Good work though, nontheless.

Many run their 6 volt starter on 12 volts with no problems, but damaged ring gears and broken Bendix springs can result. Mine always engaged too hard, and the new ring gear showed too much wear in a very short time. Converting my starter to 12 volts made a big difference.

[Mike51Merc]

My understanding is that you can simply swap in 12V field coils from a later starter and be done with it. I'd imagine swapping the field coils would make the starter spin at the same RPM as the 6V starter, which is pretty slow.

On the other hand my friends 6V starter running on 12V works real good until it breaks a bendix spring about once a year. It spins like mad, though, and sounds like a turbine winding up.