Spark plug spacer?

Mathias NY · Jan 7, 2009

Has anyone ever come accross a spark plug spacer? My 1940 Allis B has a set of spacers in it's head that recess the spark plugs by about 3/4". If I remove the spacer, the spark plugs will be flush with the opening in the combustion chamber.

What would be the benefit of recessing the plugs? I can't think of an advantage.

Thanks for the help.

RN · Jan 7, 2009

Sounds like the old anti-fouling inserts. Worn rings or guides would have lot of oil fling around spark plug tip, the spacer or insert would protect plug tip from side spray and form a small hot combustion chamber that would burn most of oil that came in on compression- keep plug clean a lot longer. RN

Rick(MN) · Jan 7, 2009

They were sold with the idea of keeping the plugs from fouling. Traded a D-17 in once a number of years back with just one in it. That tractor ended up being around and getting used a few years before it got sold. Pulled the spacer out and right away it started fouling the plug in that particular cylinder. Seemed to work in that particular situation. However, this is by no means a testamonial for them.

glennster · Jan 7, 2009

sounds like they are anti-fouling caps. it pulls the spark plug out of the combustion chamber area to keep the spark plugs from fouling out if the engine is burning a lot of oil.

Janicholson · Jan 7, 2009

The spacers are for the reduction in oil fowling that can happen on plugs. It does this by limiting the exposure of the electrodes to oil droplets 9to some extent) and by reducing the cooling of the plug (a greater extent) this burns off oil based deposits. Are they worth it. If they allow an engine to operate while burning oil on a farm where the profit margin is nor visible, yes. in reality it just needs to be repaired. If it seems to not burn modern oil, change the plugs, and remove the spacers. JimN

old · Jan 7, 2009

Anti-foulers. Probably have about an 1/8 inch hole in the bottom of them so as to help keep oil out but let the spark still do its job. Thats is a sign of bad rings and or valve problems
Hobby farm

greygoat · Jan 7, 2009

Still available in the NAPA accessories catalog,
though young counter people might not know about
them

Clefus · Jan 7, 2009

I bought a set from NAPA a few years ago for my BN ....it needs a rebuild but lets me use the tractor until I get it in......

Mathias NY · Jan 7, 2009

That makes sense. I guess I learned something new today. Thanks for the help.

There were a lot of carbon deposits in the head. I assumed that it was a result of incomplete burning, caused by recessing the plugs. I don't know how bad the rings were, because the engine was seized and the rings were corroded onto the pistons. I did check the valve guide clearances tonight. They are running .004" to .005". The service manual says that up to .006" is acceptable, so the problem was probably the rings.

Spark plug spacer?

Mathias NY

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RN

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Rick(MN)

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glennster

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Janicholson

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old

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greygoat

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Clefus

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Mathias NY

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