I have some splitdorf white porcelain spark plugs, some are marked "1" and others "775". They look nearly identical. I've seen references to the "1" plug being for a model T. But I've found nothing definitive about the 775s. Has anyone run the 775s or tell me more about them? Here are two of each.
Maybe contact these folks?
If they send you something really cool, like a Splitdorf heat range chart or a Model T spark plug cross reference chart, please post it here, thanks!
775 refers to the quality of porcelain that was used. My guess number 1 is the plug number.
If 775 is the type of porcelain of the one so marked, is the plug marked "1" a different porcelain? Are they essentially the same plug? Has anyone run either of them?
I found this catalog listing for Splitdorf porcelain plugs. It lists the #1 for the model T. But no mention of the 775 type porcelain.
Paydirt, way to go Steve!
Steve's document says that the Splitdorf plugs have a "Semi-Petticoat" design, what is that?
The table says that an AC1075 plug is equivalent to a Splitdorf #1.
Now, if we could find a similar table for other plugs, life would be good!
Is anyone running either Splitdorf #1s or AC1075s in their cars? How do they compare with Champion X's?
here is a short history of 775 porcelain
Thanks Kevin, very interesting reading.
The above catalog pages are from 1930. I just found this ad from 1926 showing a 775 Splitdorf plug. Perhaps they used 775 when these porcelain plugs first came out to capitalize on the new material, but dropped it by 1930 in favor of marking for specific applications.
A spark plug collector friend of mine said there was a porcelain manufacturer back east in the early days. Probably the Frenchtown Porcelain Co. mentioned in the link above. He said you could get any porcelain you wanted from them. You could apparently even get one with your name on it. The porcelains from that company were all marked "775". Here's some more "775" plugs. I know I've seen lots of other "makes" with the "775" on them. The one on the left is a B & B Air Cooled, Pat. Sept 1928; the middle is a Porter #3 KeepKleen with pat. dates of 1914 & 1917; and the Splitdorf with the "775" on it. I've been trying to collect up sets of the Splitdorf's for my early T's
Thanks Verne, that 775 porcelain must have been something very special. I found an ad for 775 Splitdorfs for the model T. So I'd say the 775 and 1 plugs are about the same.