Old Spark Plug information requested. (pic)

[CTCV]

Can someone provide info on these plugs. The little wire at the top brass section has two positions. When tested with a meter one position disconnects the continuity killing the spark. They were in my 32 Buick 344cid.

Tony

[Craig Gillingham]

These are Doering spark plugs, although I can't tell you much more than that. I collect spark plugs, and I have/had one once. I assumed the lever at the top was to clamp a spark wire, although it could be a cut-out?

[Craig Gillingham]

I found this photo, except it still isn't clear to me what the lever does.

 

[TerryB]

See if Terry Bond on the forum knows, he is a big spark plug collector

[Rusty_OToole]

Could the gap be a spark intensifier?

[Craig Gillingham]

I think it is a type of spark intensifier.

[Akstraw]

Looks like the lever might adjust the gap.  I have no knowledge; just speculating having looked at the diagram.  Begs the question, though:. Why would you want to adjust the gap?

[Frank DuVal]

Adjust the gap to get a fouled plug to fire!

 

Because:

 

The ignition coil produces voltage in excess of what is needed to fire the spark plug under "normal" operating conditions for that vehicle. But, the actual voltage is determined by the spark plug gap. Think of it this way, the  coil voltage rises from zero to X when the points open and the magnetic lines of flux cut through the coil windings ( a generator without rotation).  When the voltage is able to jump the gap, the voltage rises no more, as current now flows in the system from coil through wire, rotor gap, wire, spark plug gap, engine block and back  to coil. 

 

Now, with a fouled plug, that looks like a short in the system,  the voltage rises until the gap at the rotor is breeched, then stops rising, as current flows through the carbon on the plug tip/ground shell.

 

To get the voltage high enough to make that fould plug fire, you need another gap in the system to make the coil produce high voltage, hence the "spark intensifier" gap. This higher volatge can make a spark around the carbon at the plug tip.👍 Once running, maybe the carbon burns off and the extra gap is nolonger needed.

 

 

 

 

[CTCV]

Brilliant!  And very well explained. 

Thanks Frank.

 

Tony

[Bud Tierney]

Jump-spark type plugs were available at one time for oil burners;  as described above, they kept plugs firing in the oily combustion atmosphere that fouled a "standard gap" plug...

We used to make our own, holding the wire just off contact with the plug/s...