I have been wondering about this and have asked it on here and other places, as have others, with some result but never to my satisfaction. So I put my thinking cap on and came to the conclusion, that since no modern spark plug charts include our beloved Standard Twin Tractors anymore, what was needed was a vintage spark plug chart. I looked the internet over and I found nothing old. Then it dawned on me that this might be the very thing that those spark plug collector guys might be hoarding. Bingo! I stumbled across the
Spark Plug Collectors of America
Looking at the list of contacts on their page, I found the President of the club
Lanny Baron (President)
What a fine gentleman. He took the time to answer my e-mail and several others and after a while I had my answers from Lanny and his documents.
Here is part of the conversation:
I would like to ask if you or your members could be of any assistance in identifying an antique spark plug application?
I am one of few collectors of antique, walk-behind style, "Standard Twin" Tractors, made by the Standard Engine Company. I have attached an example tractor. I am not a spark plug collector, but I do have an interest in finding what would have been the correct spark plug for this application. My thinking is that one of your members may have some vintage spark plug charts that will list the Standard Twin application. Newer literature makes no mention of this forgotten company and I have found nothing online.
If you are willing and able to help, it will benefit you to know that there was a cylinder head design change somewhere in the tractors history, probably between the late 30's and 1942. The early tractor had cast iron heads and used a tapered seat plug. Most of those are now using a Champion "X" plug, which I am sure you are very familiar with. The later tractor, 1942 for example, had aluminum heads and switched over to a sealing washer style plug. Mine currently has Champion "UD-16" plugs, but I seriously doubt that they are the proper ones. I have particular interest in finding the correct number for this later, aluminum head version, but any information would be welcome.
"Hi Larry. The 1942 Champion application guide shows the 1942 model C Standard tractor as using the the Champion #7 18mm plug. I have these available at $8 each for good clean usable used ones or $15 ea for NOS. Also I have (I think) NOS #8 Champions which are slightly hotter and would be a better choice in a tractor not used for hard work. I can't be sure until I set up my vending tables at the Hershey antique car show on 10/8. They would be $12 ea."
I appreciate your help! I will probably be getting with you soon to get a set of originals for mine. Also, with your permission, I would like to post this information, along with your e-mail address on the Standard Twin Forums. That way, others will benefit and may also want original plugs from you. Please let me know if this is OK.
P.S. By chance, were you able to confirm or disprove the Champion "X" as the original application for the older tractors? Maybe 1935-1938? If not, Thank You anyway!
"Hi Larry. Sure, its OK to post my email address and letter. As long as I have a supply available I am happy to sell them. However, these are not being made and have not for some time. I usually get them from time to time but there are no guarantees that will continue. The Hershey show next month is my major selling event and I have no idea what my inventory will be after that. Sometimes I get cleaned out of a particular plug until I can find more. The Champion X plug was the original equipment in Ford Model T's, 1911-1927. They were made in mega quantities for the after market as well. They are commonly used in almost anything needing a 1/2" pipe thread plug. The correct plug for gas engines, including the Standard tractor is the Champion 31 which is a little hotter. I have them in stock @$25 ea NOS. I also have a wide variety of other makes both 18mm and 1/2". The rarer ones are of course more money but some of the 1/2"stuff is actually cheaper than the Champ 31's which are hard to find and in big demand. Hope this helps, Lanny B."
Ok Standard Twin fans,
I realize someone may already know this out there, but as far as I can tell it has never been added here. I hope this helps.
P.S. Turns out my UD-16's mentioned here were actually a correct replacement at some point.