Until I find some good era spark plugs for my '19 I decided to temporarily use the plug adapters and 14mm modern plugs. These plugs do not have a metal top that unscrews leaving additional metal above the insulator. In other words, when the metal tops of the plugs are unscrewed it leaves the bare insulator showing. If the plug wire is installed between the metal cap and insulator it leaves a gap inside the plug I assume due to the thickness of the wire end. Is it better to open the circle on the wire tip and make it fit the groove on the spark plug tip or unscrew the tip and place the wire between the tip and insulator? I hope this question makes sense! Thanks...
Maybe it adds to the gap inside, working like an old spark intensifier if you unscrew the top.. That would increase the needed voltage output from the coils and may give an extra strain on original coils if that's what you have?
One thing modified leads to another.. I think I would have used modern spark plug connectors for the wires while the modern plugs are used. My 14mm plugs has a normal thread for the connection, so you can find other modern plugs that would work with the usual wire connectors for T's
Michael, what brand of "good era" spark plugs will you accept? I've got some NOS Champion A 25's, if you can use them. I'll even deliver them. Its been a while since we saw each other.
Michael, you could use the Autolite 3095 spark plugs which have the 1/2 NPT thread for the head and a threaded top. That might help some, and it is what I run, it seems to work just fine.
Thanks for the replies. Does anyone know of a chart showing a list of the 1/2" NPT plugs that can be used on the Model T and their heat ranges? I need something hot since I putter at low speeds mostly on back roads and here in the neighborhood.
Here's a chart I found online for Champion plugs. The 1/2 inch pipe size is outlined in red.
Interesting, I've never seen Champion 32, 33 and 34. Have seen NOS 30 and 31 on ebay in recent times, and Donald McKinsey sells them.
Plugs made by Myles Standish (AAA, Horseshoe, Universal) I believe are hot...I purchased the last NOS McKinsey had.
You could also try the pink or white polonium Firestone 1/2"; and yes, Mckinsey has those too
Michael, on my 14mm plugs I used a small washer under the wire spade and that took up the slop. PK
Edison 14s run hotter than Champion X's, but they're getting hard to find.
Another way you could do it and use the 14mm modern plugs that you have is to make up another set of plug wires w/ends that fit the 14mm plugs.
If you use 14mm plugs get the ones without a resistor. I have found that the resistor type don't like the voltage diferences produced when running coils and seem to burn out quickly. I think the non resistor type end with an even number example 66. The non resistor type plugs (14mm) are getting harder to get as they are no longer a stock item so you have to look for them.
Once you have broke the connection beteen the center electrode the plugs don't seem to work as well. I had some 25's that the end liked to spin out, they gave me nothing but problems.
Michael, Looking at the chart, above, one sees that the Champion A-25 is the coldest Champion plug. I have often wondered why driver's preferred the Champion X plug to the A-25. Now, I know. I have also used the presently available Motorcraft spark plugs and they work, well. I don't know anything about the presently available Autolite spark plugs and can't give them a recommendation. Yes, we live too close, not to see other more often.
Terry, during the Model T era and for some time afterwards the Champion X plug WAS the A25. Today, they are different plugs, not back then.
How and why could the X also be the A25? There were two types of X plugs, and I don't mean ribbed and non-ribbed. One of the two types of X plugs was coded as "A25". Later on, to avoid confusion the "X" label was dropped. That's why the chart above has no "X"; the X is the A25, which is listed. The other X (the non A25 one), could be the hotter one you mention that others had prefered; these were phased out and probably replaced by the 31 or 32, etc.
These plugs are marked with "X" and "A25" both on the box and on the plugs themselves:
MK you can simply use some bosch FR9HP. I have used them and they worked very well for me. They have the screw on top as well.
You can also get some very reasonable T plugs at Rock Auto