any recommendations on the best spark plug for my 26 coupe ?
"Champion X", available at any Antique Auto Parts place, or on ebay. Jim Patrick
This can end up just like the guys who have their own preference for motor oil brand. For spark plugs though why not use what Ford originally used - Champion X.
Champion X is OEM for 1926, but I wouldn't squander the dough for new ones. Go with what you have, or if you need new plugs you can use Autolite 3095 (about $13 a set) while you acquire the X plugs on eBay or at swap meets. Don't pay over $5 unless the plug is exceptionally nice.
Here's more about the Champions: http://dauntlessgeezer.com/DG95.html
I've tried all the mentioned plugs except the original X plugs. Can't seem to find them anywhere around here at auctions and thrift sales. I settled on Motorcraft F11 plugs for my '26. Gapped at .032, they run slightly better than the others for me. My only issue is getting good ones. Last time I ordered them from my local parts store, it took 3 re-orders to get 8 good spark plugs that didn't have center electrodes so far off center that the ground electrode couldn't be bent enough to make them serviceable. Another testament to the dubious quality of off-shored parts manufacture.
For my driving experience, with high compression heads, the Champion 25 is giving good service.
Gapped to just slightly over .025" (i.e. the .025 gage wiggles out).
Only thing is take care in tightening the wire nut. No pliers Do it the old way, snug nut over the wire terminal, then hold nut, and push terminal forward slightly to tighten enough. The Champion 25' uses a small thread electrode that is just cemented to the inside of the porcelain.
Dab of anti-seize on the threads too makes removal easy, don't over tighten in alum heads either, just snug down those pipe threaded plugs.
This interesting thing happened to one of my Autolites. I once had the same experience with a Motorcraft plug. Apparently their posts are glued in.
If I wasn't cheap---I mean thrifty, I would use the Champion 25's, just because it is what's right.
I however, have used a mixture of plugs, Autolite 3095, Motorcraft F-ll (sp-465), and the "modern" Autolights with the 1/2 NPT to 14mm adapters. I seem to get the same performance from all of them, and have no failures to date.
So as was stated above, to each their own. Opinions will vary.
https://www.google.com/search?q=what+spark+plug+to+use+mtfca&rlz=1C1CHBD_enUS737 US737&oq=what+spark+plug+to+use+mtfca&aqs=chrome..69i57.5400j0j7&sourceid=chrome &ie=UTF-8
I ran a set of repop Champion Xs in my '23 for 20 years. No trouble whatever until one day 9 years ago I pulled into my brother's driveway and all of a sudden I thought that somebody had fired off a 30.06 under the hood. The #2 plug's porcelain had exploded into powder. I replaced it with another X, an original. Should be good for another 20 years, though the car has mostly sat since then.
I have had fantastic luck with Motorcraft F-11's, you can't wear them out and you can't beat the price.