What would be the correct spark plug for a 1925 Ford T 4 door?
Champion X. The correct one for 1925 is #5. You can get the current version, #6, at O'Reilly for about $20 each. Or if you're more patient you can find good ones like #5 at swap meets for less than half that.
The Champion X became the standard plug about 1912. By then the ribbed version was being made. I just prepared a paper about Plug performance. Send me an Email and I'll forward it to you. Doug Dachenbach
Doug where did you find the documentation for ribbed plugs in 1912? All the Champion advertising I've seen shows them without ribs until after 1920.
I like these. Not OEM, but good conversation starters.
Are the new Champions worth the twenty bucks a plug when there are Autolites available for around three?
After using autolites i found i like champions a little better. And easier to clean.
I know that about 1912 Henry gave the contract to Champion and I think it was an exclusive for some time. The X was developed about 1909. I don't know when the ribs were added but I thought it was pretty early but I don't know where my presumption comes from. If I find a reference, I'll get back. Did you know that the ribs are to give the plug more surface length and reduce outside fouling? Useless trivia.
Champion X's are worth every cent you pay for them.
The same "used" set I cleaned up in 2004, are still working well in my car. It starts easier and idles smoother with them than any of the modern plugs with adapters. As a result I wont use anything else.
When you're on a good thing, stick to it.
A couple of years ago, I happened across a garage sale that had 5 gallon buckets of old spark plugs. After examining them, I came to the conclusion that, in general, early plugs seemed to be smooth sided up until 1920-22. AC had a model or two that had one large rib at the top prior to that. The ribbed type like the Champion X's we have commercially available today, came in about 1923 or so (a guess). If you Google 1925 Champion Spark Plug, with Image, you will find original ad's that show the ribbed plug. I was particularly interested in what plug would be right for my 1915-16 Oakland. As best I can tell, it was an AC. I figured that out by looking at old spark plug ad's on Google Image.
The last set of the 1.98 Autolites from Advance Auto I bought were no good. Leaked around the joint between the porcelain and metal base.Got dirty quick to. The factory was moved to mexico. The 1's that were US made didnt give this trouble as I put the old set back in when I had this issue arise.
Some of the non-Champion modern plugs have terminals that are glued into the plug and may fall out. VOE.
Bosch 409 good modern plug with 14mm adapters but old X's seem run best and the new x's second
Ofcourse my x made me run away just fine
I found that with some of the modern Champion 25 if you over tightened the nut the terminal would screw out of the body. Course I have had a number of old Champions that the screw part would twist off, see a good number for sale with that issue from doing the same thing.