MTFCA Forum

Posting a few random questions this evening, What is the proper gap for the spark plug?

I believe that .025 to .030 usually gives good results.

Jonah D'Avella wrote: ↑

Sun May 08, 2022 8:55 pm

Posting a few random questions this evening, What is the proper gap for the spark plug?

Depends on the spark plug and engine modifications.
For starters what brand, model and year of manufacture of your plugs? Reason for the question:
Hundreds of brands were made for the Model T. Some owners used vintage plugs. Currently there are a few available.
Year of Manufacture is that Champion X plugs have gone through some redesigns and members have preferences (X, A-25, 25).

You will get many answers. Save everyone time and just Google
https://www.google.com/search?client=fi ... +MTFCA.COM

Depends on whether you're running stock ignition or a distributor - I set a .025 - .030 for stock ignition - distributor ignition .032 - .035.

The directions for the Champion X spark plugs says .025. On the advice of a member of the forum in 2010, I had mine set at .030 for years and the engine did not run well. It was only when I re-read the instruction sheet that I realized they were set wrong. When I reset the gap at .025, the engine ran beautifully. Jim Patrick

Outside magneto is .018

jiminbartow wrote: ↑

Sun May 08, 2022 11:12 pm

The directions for the Champion X spark plugs says .025. On the advice of a member of the forum in 2010, I had mine set at .030 for years and the engine did not run well. It was only when I re-read the instruction sheet that I realized they were set wrong. When I reset the gap at .025, the engine ran beautifully. Jim Patrick


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I found over .025 would spark intermittently using a champion plug tester @ 80#. Had 1 plug needed .024 to fire consistent. Champion used a25 plugs. Ran well after resetting for a 35V magneto output ignition. I do set distributor plugs @ .032

Back in the day, if you had no feeler gauge (and few people did have one), the thickness of a hacksaw blade was deemed sufficient. Every workshop had a a broken hacksaw blade!

Plugs- one thin dime. Points- matchbook cover. bobt

Pardon me on my last post. Matchbook thickness to gap points is NOT meant for model T's. Sorry. bobt

On the side of the road with no tools - the thickness of your thumb nail works too.

Somewhere between .025-.030 is a good general setting for me. I have 3 T’s and they are set for the quirkiness of each T.

To me it’s like finding a setting that’s right for the carb for your paticular car. And we all know it’s not exactly 1 1/4 turns for every T!