ORIGINAL: small_rcer
I have just looked carefully at a Nelson plug and 049 adaptor.
If one used a lathe, it looks like the diameter of the threaded portion of a Nelson plug could be turned down. The tapered seat face could be reduced by about 1/2. This would then allow you to re-thread the outside of the formerly threaded portion, down to a size to fit a newly designed 020 head adaptor or even a used 020 plug itself. The question is how much meat is there inside the Nelson plug to for allow this reduction in diameter? Is there a large cavity for the stem sealing material such that there would be no material after turning down the body?
What about the turbo plugs being similarly turned down to a suitable smaller diameter for 020 or 010 use? I don't have any Turbo plugs to examine. Would a conventional glow plug be small enough for the 010? I am looking at one and it appears small enough in the threaded portion. Has any one used a conventional short plug and made up an 010 adaptor?
Just some thoughts on a quiet night.
Jim H
Jim,
Some interesting ideas. The problem with any kind of adaptor for the .010 is that the relatively large cavity compared to the stock plug would add that much more volume to the combustion chamber. This could be corrected by facing down the plug, of course.
Use of a conventional plug in any sort of adaptor guarantees a large loss of power, unfortunately. This is why the turbos are used, they don't have that flaw. That's a good idea to turn down the body of a turbo plug and re-thread it. But while the .020 Cox head has enough meat in the diameter, the length doesn't give you a lot of threads to work with. An entirely new adaptor really does have to be made from scratch, as per the link.
But both heads are so small,,, what may happen is that CS, who bought Cox's tooling, may just be able to make these plugs for us at a better price. We can hope.