BOSCH SPARK PLUG, 1914

Early spark plug for Petrol Engines.

Your comments:

• It is 18mm thread for mainly older side valve cars. The electrodes were set around 18-20 thousandths of an inch apart when used with a magneto. If a coil and distributor was used then the gap increased to around 25 thou.
  The same pattern of plug shown is still made today. Earlier ones had mica for the insulator instead of porcelain. Many were made of sections that could be taken apart to clean. J.M.
  .......... jim mortimer, SNAINTON. Yorkshire. U.K., 7th of July 2012
  
  

A0326