Model A & B

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Brumfield 7/8-18 Inch Spark Plug Listings

In many postings on internet message boards, Larry Brumfield has shared a lot of his knowledge about engine operation, combustion, intake and exhaust theory, and cylinder head design, construction, and manufacture.

His cylinder heads were produced and sold for many years with nearly all customers reporting great satisfaction and trouble-free service.

Many thanks to Larry for providing the 7/8-18 inch spark plug heat range information below, and allowing it to be presented on Ford Garage!

Here are Larry's latest 7/8-18 inch spark plug listings:

Spark Plug Heat Ranges:

Champion recommends the W-18 to be the modern replacement for the 3X as their heat ranges are fairly close.

Concerning the W16Y, according to Champion, the W16Y, being a projected nose plug, is hotter than the W18 or even a W20 at low speed but cooler at high speeds over 5500 RPM... which obviously will never apply to most Model A’ers. However, most people report that the W16Y runs cooler than the W18 on a Model A at any speed.

I doubt very seriously though that Champion’s engineers were using a Model A engine, as these plugs will work in several different engines, and their results would no doubt be determined under controlled conditions where the air/fuel ratio, spark intensity, etc., would be near perfect which is not the case for most Model A's.

So it's still best to use the following as a general guide but do your own heat range tests and reach your own conclusions and opinions when running any of these plugs in a Model A engine.

Champion (hotter down to colder):
W95D
W89D
W16Y (For Model A engines it ought to be nearer to W14)
W20
W18 (About equal to the original 3X)
W14
W10
W85N
W80N

Also the original 3X which Champion lists as normal along with the W18.

Motorcraft (hotter down to colder):
TT15 (the same as Champion W89D)
TT10 (the same as Champion W14)
TT8 (the same as Champion W14)
TT4 (the same as Champion W10)

Autolite:
3076 (the same as Champion W14 and Motorcraft TT10)

Mopar (hotter down to colder):
P-9-7S
P-9-6S
P-9-5S

Prestolite (hotter down to colder):
78-10
78-8

Stitt (hotter down to colder):
137 BSP
197
147 B
13/10

Larry Brumfield
August 2016


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