MTFCA Forum

Does anyone have experience running these 360 one-point style plugs? Will they work in a T?

Those particular plugs do not have 1/2" pipe thread. If you found bethlehem plugs with pipe thread, there is no reason the wouldn't work.

Frank

Mr. Iaccino, It doesn't look like the threads are tapered on these plugs but they measure 1/2". Does this mean they will not properly seal? Would a copper washer maybe help?

No, you need ½" pipe thread. It looks like this.

Notice the slight taper. It doesn't take washers.

The thread on those appears to be straight. If they measure approximately 1/2", they are most likely 14 mm. The threads will cross and not provide a proper seal....

Frank

A 1/2" male pipe thread measures 3/4" OD, or a little more.

Thank you all for the input, I passed them up for the reasons you provided. But if anyone is still interested they are on T-bay for sale, six of them tested.

I'm reviving this thread because I found more examples of this 1/2" straight thread plug NOS labeled "Ford Special". I bought them so I will test them out on a T, not sure what other kind of Ford applications there could be? It's trivial but fun to do these kinds of experiments.

Cant read the thread on the label. If they are not 1/2 pipe thread, they wont work.
If you insist on trying them, leave the hood off & stand clear to start.

Possibly, you could use an adapter that goes from 1/2 in pipe thread to 14 mm. Langs, Snyders and other vendors have them.

Art Mirtes

Model "A" possibly. JIm

Anything with a flat shoulder at the top of the threads and a seal is not a pipe thread. If it says “Ford Special”, either that means “Model A”, or the wrong spark plugs are in the box.

Pretty sure Model A are 18mm or 7/8".

speedytinc wrote: ↑

Wed Jan 25, 2023 10:38 am

Cant read the thread on the label. If they are not 1/2 pipe thread, they wont work.
If you insist on trying them, leave the hood off & stand clear to start.

ONE BOX says 1/2 doesn't mean the others are Discussion from an old thread not box colors are different --
-- By Donnie Brown North Central Arkansas on Monday, June 04, 2018 - 09:06 pm:
I tested the "fire ring" plug in a Model T head. The threads just fall into the hole and are a "sloppy fit" (hillbilly technical term). So they obviously do not fit a Model T
I did not have a metric thread gauge, but the thread count/pitch of the "fire ring" plug is between 16tpi and 18tpi. so I assume it has Metric threads. I measured the outside diameter of the threads to be 0.705.
That only leaves V-8 Ford and the early "letter" series cars, if these are to fit some Ford product. Maybe someone knows what the size of the V-8 plug or the "letter" series plugs are ?????
I think Dale is correct about them being motorcycle or aviation plugs.
Possibly there were several sets that were labeled wrong back in the day. That may be the reason of these surviving in their original boxes. Some dealer may have just stuck them on the top shelf and forgot about them when he found out they were incorrect and had no market to sell them to . ????
These may be super rare, but I probably will never know for sure what they fit. They do look nice with the other spark plugs I have.

per Donnie's measurements, those threads are m18 x 1.5

it is a perfectly standard 18mm spark plug.
Find an engine which takes 18mm plugs and knock yourself out.
A 1933-37 FORD should suffice.

I have that size tap in my ollection and now I k own why.

Art Mirtes

Art

old spark plugs and O2 sensors on modern cars.