Altenator/Starter Issue

[Colonel Biggs]

A friend has been restoring a T fire engine, which he has converted to an A frame and block. I assisted in the conversion of the wiring. Started up and ran like a charm. Because of the electrical power demands that he has since added, he has installed a Powermaster alternator and a 12 volt coil. He was told that that these are plug an' play installations, and that he should still be okay with the 6 volt starter.

When starting the engine recently, his foot slipped off the starter pedal twice. The starter evidently locked up, and he had a bear of a job removing the starter from the vehicle. (Locked up on flywheel, perhaps?). My question: is a 6 volt starter compatible with a 12 volt electrical system?

[Badpuppy]

Not really. It should be rewired for 12V. That being said many have used 6V starters in 12V systems for years.

[Ruth]

IF you continue to used the 6 volt starter I recommend installing a modern starter drive. https://www.snydersantiqueauto.com/p...6183&cat=41746

Best would be to convert your starter to 12v AND install a modern starter drive. 12v field coils are available. https://www.snydersantiqueauto.com/p...d=976153&cat=0

[Herb Concord Ca]

You should follow Ruth's second suggestion.

[MAG]

Agree with posts #2 &#3.

[Colonel Biggs]

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Thanks for the responses. Never having use an alternator, I didn't want to play master electrician. In years past, when installing new field coils into generator rebuilds, I have found the coils somewhat enlarged, which sometimes interfered with the armature. Is this also true of repro starter coils, or are coils being wound tighter today?

Again, thanks for the responses!

[31Tudor]

I will be the contrary one then. I run a 6 volt starter, with a 12 volt system and alternator, on my speedster with a 7:1 head. Also using the original starter bendix. I have 9,000 some miles on it, so obviously a lot of starts in that 9,000 and have not had a starter issue. I am not guessing or assuming anything, this has been my experience.

[jack backer]

I’m with 31 Tudor… 6v A starter handles 12v no problem, second Ruth on the modern Bendix, it’s cushioned, doesn’t bang like the stock Bendix. Been running that combination on a modified A engine,7.5 to 1 Winfield red head for a few years.

[Keith Alvin]

From what I have read/watched some say you don't need to bother. Another guy I watched this morning had examples of broken starters and a ford service bulletin from 1955. He was adamant that they be a 12 volt starter.

[MAG]

I had 3 cars come into my shop with the starter ring off or coming off the flywheel (one was my car). All were running 12volt systems on 6 volt starters.
Not sure if the 2 other cars had original starter rings installed. Mine had a new starter ring installed at rebuild and had 10K miles on it when it started to come off. Was lucky enough to catch it before it came completely off. A new style bendix is installed. Converted starter to 12 volts and have another 10/12K miles on it with no problems. Not saying it will happen to you...but..it can.

[Synchro909]

I have seen too many starter motors running on 12 v without conversion with bent shafts. If you run a 6 v starter on 12 v you WILL bend the shaft eventually and dislodge the ring gear.
Also, I have thrown away every one of those modern drives I had. They don't engage the ring gear properly and ruin it in short time. IMO, running a starter on 12v with one of those drives is a recipe for disaster as MAG has found.

[The Master Cylinder]

It appears everyone has a little different experience. I have been running 12v for about twenty years. After distroying a couple of original starter drives I installed a modern drive about 15 years ago and have not had a problem since. About 5 years ago I rebrushed the starter and installed 12v field coils at the same time just because I felt it would be easier on the whole system.

[rotorwrench]

The 6-volt starter running on 12-volts gives it a pretty heavy duty increase in rpm over the normal voltage. These old motors have heavy flywheels and clutches that were designed to start at a lower rpm. The armature shaft isn't all that big a diameter and it's a long one so a bent shaft becomes a reality on 12-volts. A person has to remember to retard the spark for sure. A kickback at that rpm can be catastrophic.