MTFCA Forum

Would like to use this German Bosch ZR4 two-spark mag to fire a T OHV head with 8 plugs on an American Bosch Ford Magneto side-drive as seen in the photo below. I only have German Bosch mags (higher quality, hotter spark, and more reliable) and don't have an American Bosch unit to measure. I'm aware of racing side-drives w/a water pump, but would rather go with a simpler American Bosch drive.

The German mag's have a 44 mm shaft height and this ZR4 mag base is 5-1/4" long from the bottom foremost edge of the bronze front cover to the back of the rear cover. Anyone have both an American Bosch Side-Drive and an American Bosch magneto (the shaft height maybe different) which they could measure and compare for me? Thanks in advance if you can help.

I read somewhere that the company name was changed to "American Bosch" on account of the Lusitania outrage and subsequent events. I'm sure that such a strategically important operation would not have remained in German control in those times. It may be that the product did not change, other than the company name. If I understood what I read correctly, the Bosch products sold in the USA were being produced in the USA prior to the war and the name change.

Pretty sure the shaft height is the same on all Bosch mags. I ran a Bosch AT4 on a single gear side drive for many years. Even the Stutz /Pierce Arrow Twin ignition units are the same shaft height has the mags. I have a single spark ZR4 American Bosch listed in the classifieds at the moment- I will measure the shaft height and report back.

TXGOAT2 wrote: ↑

Sun Feb 13, 2022 5:29 pm

I read somewhere that the company name was changed to "American Bosch" on account of the Lusitania outrage and subsequent events. I'm sure that such a strategically important operation would not have remained in German control in those times. It may be that the product did not change, other than the company name. If I understood what I read correctly, the Bosch products sold in the USA were being produced in the USA prior to the war and the name change.

Thanks for you reply, you where really close, although the name change was a few years later. I did some research last night and found that Bosch was taken over by the US government at some point during WW1 by the "Alien Property Custodian." It was was sold in 1918, and became American Bosch in 1919 and was listed on the NY Stock Exchange. I'll post more about it later.

Dan McEachern wrote: ↑

Sun Feb 13, 2022 11:23 pm

Pretty sure the shaft height is the same on all Bosch mags. I ran a Bosch AT4 on a single gear side drive for many years. Even the Stutz /Pierce Arrow Twin ignition units are the same shaft height has the mags. I have a single spark ZR4 American Bosch listed in the classifieds at the moment- I will measure the shaft height and report back.

Thanks Dan, I did see your mag earlier, and look forward to hearing what you find out.

TXGOAT2 here are the details of the changeover from Bosch to American Bosch in 1918.