3 piece spark plugs

bob ward

These three piece spark plugs (this one is out of a 35 H8) were an aftermarket spark plug, they were bought because they could be dismantled and cleaned at home in a time when spark plug cleaning was frequently required.

When did they disappear from the market, I'm thinking late 50s early 60s?

EssexAdv

I don't know exactly when they disappeared. However, I have a 1922 brand X car which came with AC plugs. The original plugs were 3 piece as you described. Another advantage is that the porcelain part could be replaced when they went bad and you had a "Rebuilt" spark plug. This kept you form having to buy the metal pieces. Very frugal!

As far as removal from the market.... they stopped being practical at some point when the compression rendered the take-apart design impractical to seal.

Geoff

I suspect the real reason would have been cheapness of construction of one piece plugs