I have a 1938 Chevy with the original 216 engine. I converted it to 12 volt, then blew the head gasket. I had the head milled down about 9 thousands, and put it all back together. After trying to fire up the engine, the starter gave out.

I pulled the starter apart and notice the brushes are still good, but looks like the armature appears to be fried.



I got another starter and it did the same thing. I have never had this happen before. Have any of you ever run into this problem?

I also have a one wire alternator hooked up to it. I have a wire running from the alternator, to the ammeter, then to the starter hot lead.

Any help would be appretiated.

How long were you engaging the starter each time that you tried to start the car?

I tried a few seconds at a time, after about 5 tries, the starter gave out.

Modiol,

Doesn't that armature look like it's been physically interfering with a field coil or both coils? What do the coils look like?

Is there someone over in Sac who repairs antique electrics? I have a Ford 8N tractor that could benefit from a generator going through. I don't have a mica undercutting attachment for my lathe or I would do that project myself.

The inside field coils appear to be in good condition.

Does look like ( in your photo ) that something is interfering...Rebuilt starter's are not all equil...I get mine from "Pep Boys" and there guaranteed for life...I would imagine when you went to 12 volt you went with a 12 volt starter as well...I think your just having a bit of bad luck...

As for bruno's comment on "undercutting mica attachment" I haven't the foggyist idea of what you mean and I do loads of work for my electrical guy on my lathe...Clue me in, please...The only cuts I take are on the copper where the brushes ride...Or, I shorten armature shafts and re-key them for different starters that can't be abtained any longer...

Under cutting mica is removing a small amount of insulation between the copper segments. This can be done on a lath with a properly shaped cutter and moving the carriage back and forth.
Al

This is done after the commutator is turned. The mica is an insulation between the bars and if it isn't done the mica could prevent the brushes from making a good contact. The is usually done by running a hack saw blade between the bars or using the tiny saw blade on the armature lathe that is there for that purpose.

The 1867897 umber on the armature is an obsolete number for a 1938-1954 starter armature. The later number was 1917855.

Okay...I believe now what you mean...Its those groves you don't want the grafite from the brushes to clog and cause problems where the groves should be...You can easily do this by indexing by hand and mounting the high speed sharpened tool on it's side in the tool holder ( Aloris type ) and from the tail stock run it once towards the headstock...Then back off...Don't drag it back...Use the same high speed tool you would use to resurface a flywheel...45 degree, little if no radii...

Gotta tell ya though, I've done plenty and never had any problem...

I leave the mica there...And, I learned from the "dutch" masters...They didn't clean them out...I do scratch a little out...

And, I think it just wears brushes down faster...You think mica is an electrical conduit..? If it was, then the theory as an insulator is all wrong...

In other words...It keeps your brushes wearing and making good contact...

As a general rule, generator commutators are undercut, starter commutators are not. A starter commutator should be undercut if someone has already undercut the commutator previously.

You got me there...I don't see the difference...The cut is typically very minimal...You can use sandpaper in a bind...But if that's what you say...It didn't make any difference to us...

Wait, I do see a difference...Your generator is turning all the time...Brush wear is important...

I don't think were helping the starter question...lol

If you look at a new old stock generator armature the segments on the commutator are undercut but on a new old stock starter armature the segments on the commutator are not undercut. The difference is that the generator uses carbon brushes and the starter uses hard copper brushes. Also, a starter does not turn fast enough or long enough to require undercutting.

You're right...

I think everybody is missing a key point here, which was made on an earlier post, but ignored.

This is a 40s / early 50s armature -- six volt. It's being used in a twelve volt system. Wouldn't that fry the armature, especially for longer cranking cycles? I know you can get away with occasionally jump starting a 6V with a 12V battery, but not for daily use.

All the Best, Chip

There is no real problem starting on 12 volts as long as the starter motor is not engaged for extended periods. It is the heat generated in the starter that kills them.

Well...Yes, I inquired as to if the starter had been switched as well...There's a load of things to do when switching over from 6 to 12 Volt...And as we all know, IT just ain't worth it...6 Volt is fine...I've done a switch over on my '53...What was I thinking...? Young and stupid...Bulbs, heater motor, coil...Geez

Plus the battery...And you know what...? I got wise and switched it back to 6 volt...

This discussion comes up every few months or so, and we pretty much are all in the agreement that 6 to 12 is a bad move...Life's to short, yada yada...There are other improvements you can spend your time on than screwing around with a 6 to 12 volt system revamp...IMO

Now, I recall back in the 'ol days jumping 6 volt battery's with a 12 volt battery...On farm equipment and such...Heat is a big factor...Best start up right away...The 6 volt battery didn't seem to care for it much, either...Clamp it just as the key turns and then get those cables off...

Yes, you can use a 6 volt starter on a 12 volt system for daily use. Not a problem as long as you don't engage the starter for extended periods of time as Chipper mentioned. It is normal when converting from 6 volts to 12 volts to leave both the 6 volt starter and the 6 volt generator in place and use them on the 12 volt system.

You have my tiny brain confused JD...Sounds like the only modifications are...Well, the battery...Coil...? Lights...?
Smaller battery cables...? I didn't have a problem with the sending unit, as it didn't work anyway...

While there are many reasons for converting to 12 volts i..e., air conditioning, music setups, faster turning of engine for start-up, brighter lights, etc, I have found that the old 6-volt system works well enough for me.

So, my point is that maybe converting to 12-volts is not worth the annoying little problems that may accompany it.

Charlie

Back to the original question...

I called a shop here in Sacramento. They rebuild starters and generators. They believe the armature is spinning too fast with the 12 volts. They can rewire the armature, and replace the field coils so it will be 12 volt compatible. I will have them rebuild it and let everyone know how it works out.

Thanks again for everyone's help.

Can't you find a 12 volt starter that would fit without the expense of having that one rebuilt...?

Charlie Don't know about your 6 volt starter...Mine cranks pretty fast...
Perhaps I'd better check the compression...Wait, I did that a while back and it was mostly around 95-100...

If you want a 12volt starter you need to install a flywheel for a 12volt. I believe it has more teeth than the 6volt flywheel.

Take a look at the armature in the very first picture in this thread. Notice that one of the wraps is bent over and has been dragging on the field coil winding. Looks to be over 1/2 of the material scraped away. Fix or replace the armature for an operating system.


PS: Complete generator needs to be restored. Obviously the bushing/bearing is worn out.

Leave the 6 volt generator in place when converting to 12 volt system?? That's a new one on me, Pooch. How does that work?

Mike

One of our club members has a 6 V starter and running a12 V system. Has used the car for years with no problem. turns over fast and dosen't sound like a Chevrolet starter.

The 6 volt generator will work just fine on 12 volts so there is no need to change it out. I had a 1951 1 1/12 ton truck that was converted to 12 volts but the 6 volt generator and the 6 volt starter remained. Ran that way since the early 1960's. No problem. My 1946 Oliver bulldozer was converted to 12 volts as well before I bought it years ago and both the 6 volt starter and generator are still onboard. Both have been working fine all of these years.

By the way, the generator doesn't care if it is positive ground or negative ground either....as long as it is polarized for one or the other.

Dog,

Can you explain how a 6 volt regulator works with a 12 volt battery or do you change to a 12 volt regulator? I ask because I have a 1952 Ford 8N tractor and the electrical system needs updating. Others with those tractors update to 12 volts with an alternator. It would be nice to keep the OEM generator and use a 12 volt battery.

This tractor is actually used regularly to keep my long gravel driveway smoothed up with an angle blade during the rainy season.

Change to a 12 volt regulator.

I got the starter back, new armature, replaced brushes and bushings, and installed new 12 volt field coils. So far starter has been working without any problems.