Starter Pinion Gear

[Alan Winer]

I am doing a 6v to 12v conversion. I have a 6V starter and a 12v starter, both are Bosch. Both pinion gears have the same OD and both have 9 teeth. I was under the impression that the 6V & 12V pinion gears were different. Perhaps the 12V starter had it's pinion gear changed, I am not sure of it's history.
Is there a way of determining whether the pinion gear is for 6v or 12v? (I am aware that u can use a 6V starter with a 12V solenoid)
Thanks,
Alan

[Martin Benade]

Is the pinion shaft diameter the same on both? I think a 12V VW starter has a smaller diameter shaft, while a Porsche one is the same diam as the 6V one.

[Geoff Fleming]

Yes, the shaft of the 12v starter is quite smaller diameter than the 6v version. Not sure if the VW or Porsche units are the same. On my ( former), factory 12v '63 coupe, I used a 6v starter with a 12v solenoid and it worked perfectly for over 25 years.

[Alan Winer]

So the pinion gear is the same size and the shaft diameter is different. I will check in the morning.
Thanks,
Alan

[Martin Benade]

Geoff it sounds like the factory shaft diameter is the same if you used a 6v in your 12v car. The small shaft one is VW.

[Alan Winer]

Both shafts measure the same diameter and both are compatible with the 356 6V bushing.
Thanks for the input.
Alan

[Jim Karaba]

Are you sure the 12 volt starter is actually a 12 volt starter or is it a 6 volt starter with a 12 volt solenoid installed. That is one way to convert a 6 volt starter to run in a 12 volt car. Look to see if the starter case says 12V stamped into it also. A true 12 volt starter will have 12V stamped into the starter case and the solenoid.

[Alan Winer]

I'm sure it's a 12 volt starter.

[Albert Tiedemann]

Yes, the shaft of the 12v starter is quite smaller diameter than the 6v version. Not sure if the VW or Porsche units are the same. On my ( former), factory 12v '63 coupe, I used a 6v starter with a 12v solenoid and it worked perfectly for over 25 years.

"

When I restored my Speedster in 1999, I transplanted the engine, transmission, brakes, steering box and voltage regulator from a 1964 C coupe that had a12 V factory installed electrical system. I was fortunate enough to find a NOS, Carrera 12V wiper motor for an A car which enabled me to fit the wipers without alteration. When I had the starter motor repaired, I informed them [the repair facility] that it was taken from a 12V Factory installed electrical system and that I had read much on the 356 Talk about fitting 6V starter motors into 12V system cars so I supplied them with a new 12V solenoid--a round one just like the one that was taken off. Now, I know that I gave them the starter motor taken off the car that I had the complete history thereof, but when queried about the need for a 12V armature, I was informed that the part number used by Bosch was the same for both voltages. This did not seem exactly correct to me, but I took it, and installed, it and it seemed to work fine, but not as well as I remembered when installed in the original car--certainly not the length of service that Geoff claims. It was soon after this repair that I decided that the starting function seemed to be a bit aggressive on engagement so I opted for the 12V starter motor offered perhaps originally for VW, but with the pinion installed for the Porsche 356. There were a lot of initial.problems with axial gear engagement with this combination which were finally worked out but not after it has ruined a flywheel. NLA replaced the starter unit with the design flaw. I should have had them replace the flywheel as well, but who wants to argue contributory negligence. My recollection is that the housing was stamped 6V which bears out Geoff's comment. I probably still have that unit lying around. I will see if I can find it.