by Richard A. Day Jr.
All gaps unless otherwise noted are .030"
Engine Model | Plug Type |
NK, F, PB, PAL, LH, PH45, PH75, PH120, | 7/8" 18 Thd W-18 |
PH135, PH150, | 18MM with gasket ½" reach D-14 |
PHC 7/8" Heads | W-10 |
SK, GW, LLH, ZR, PNR, PH134, IH60, M60, YT, HH, BHT, | D-16 |
BHW, BH-25 A little hotter heat range than the D-14 | D-16 |
134, 230, 320, 339, 404, 240, 264, 308, 461, V345, V549 | D-14 |
M265 | D-14 |
M304, M345: Normal service | UJ-6 |
M304, M345: Light service | UJ-8 |
M196, M265, M392, M549, M345B, M392B | UJ-6 |
PW-27 18mm heads | D-21 |
PW-27 14mm heads | UJ-10Y |
Y304, Y345, Y392 | UJ-6 |
P302, P351, | UF-9Y |
PB-V-215 V-8 Model (Gap .035) | L-7 |
MD188, MD301, MD301SM (Diesel) | AG-40 |
The above information taken from a Champion Spark Plug data sheet published in 1970. One needs to keep in mind that the very early jump spark engines used ½" NPT plugs like the Ford, Model T "X" plug. Early engines such as the NL, NR, PNR and ZR series used 7/8" plugs such as the W-18. Later production used 18 MM plugs such as the D-14 or D-16 Things like heat range were never even a consideration in these engines. The YT series will be found with heads using either 7/8" or 18mm plugs. So use this data with attention to the actual dimension of the threaded hole in the engine.
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