MTFCA Forum

Which is of the three spark plug brands offered by T parts suppliers is hotter: the Champion, Motorcraft or Autolite? Is there a spark plug (1/2" tapered thread or 14MM thread w/adapter) that is hotter than any of these?

Manufacturers' websites may have information on heat ranges.

In most cases, plugs of various brands and types are available in several heat ranges.

In most cases, the plug recommended by the engine maker, or that plug's equivalent, gives the best results in general service.

Going with the 14mm plugs; Sure there are different temperature ranges, the different brands should have that information on their pages. One thing that I have found, if going with the 14mm plugs and running on magneto, get the non-resister type, they don't have an "R" in the number. I have found the resistors don't seem to play well with the magneto voltage that is all over the place.

I'd stay away from resistor plugs or any kind of "suppression" plug wire on a stock T system. I tried using a portable radio in and around my T with the engine running. To my surprise, I was able to listen to most AM stations with little interference. FM worked great. The 40 year old AM-FM-Shortwave portable radio was running on internal batteries, and not connected to the T system.

Some people use a hotter plug than recommended if the engine burns excessive oil.

Art Mirtes

What is the recommended 14mm plug? Brand/part number. Running a distributor on this one.

Compression ratios too have a lot to do with heat ranges of the spark plug. A cold range plug does not operate the same with higher compressions.

Just Sayin'

Hank

My one and only experience with 14mm spark plugs was very disappointing. I used the hottest I could get. Top speed was reduced and the exhaust ran red. Maybe it was because the electrodes don't extend into the combustion chamber to the same extent as the proper plugs.

Yes John it does as the adapters with the plugs actually lowered the compression just by a little and cause a heat shunt. Second.., your manifold getting red is another byproduct of the plug gap/timing/or mixture not being in sync with the change. You have to use a long reach threaded plug with adapters to maximize the good effects. The adapters with the shorter plugs act more like an "anti-foul" adapter.

Hank