Charlie England wrote:

Back in the bad old days when cars ran leaded gas & transistors were only found in spacecraft, there was an after market plug with construction known as 'surface gap'. The porcelain filled the area between the electrode & thread body. The 'gap' was the distance from the electrode to the thread body.

Anyone know whether these plugs are still available? It would seem that if nothing else, it might make cleaning the lead a bit easier.

Charlie

J.C.Whitney used to be a source of such a plug. 
All I can find there now is their "E3" plug,
which appears to be merely a "standard" plug with
three electrodes instead of just one.  Then too,
I didn't find any listing at all for the RX-n
engines. 

Dale R.