I'm trying to mate up an old flathead I got from one source to an old 52 F1 I got from another. The 52 had been updated to 12v. Not sure whether the flathead came out of a truck that had been updated to 12v or was still running 6v. How can I tell if the starter on the flathead is 6v or 12v? Are they similar looking with a different # on the casing? Or is it a different animal altogether?

 

More than likely its a 6 volt, which is ok using a 12 volt system, as long as you don't grind on it a long time. You can however buy flathead starters that have been converted to 12 volt. One way to tell, is hook it to a 6 volt battery, if is 12 volt, it will turn real slow, if its still 6 volt, and hooked to a 12 volt battery, it will turn really fast.

 

So I won't fry the thing if it's 6v hooked up to 12v battery and I just try a few times to crank it?

 

Hook it up to 12V, it will run just fine even if it is 6V. They're tough. Like the girl said just above, don't crank it for long periods of time.
I have a six volt starter running in a Ford tractor 12V conversion, been running that way for years. Come to think about it I have two of them running. My son has the other.

 

Thanks for the clarification. I'll give it a try.

 

My father changed my current F6 12vt neg gr around 1960 If I remember
gen regulator came out of a 1957 car. 52 Years same 6vt starter never
been touched except one starter drive, wife pushed button while it was
running broke the spring. One thing you will like with 6vt starter, its
running as fast as you push the button like an instant.

 

I've had three flathead engines converted to 12 volts and running for years now. No starter issues whatsoever. Back not long after I made the conversion on the first one, I read on some "expert" forum that I would soon break the starter bendix spring and burn the starter out. I purchased another starter, and spring off ebay and put them in a box that I carry in the trunk of the car. I suppose I have carried those parts for 30,000 miles or more today....slim