Warning, The Ols Champion Number AER-72S was the spark plug for the M-715 OH Cam Tornado Engine, only. It is 1/2 " Reach, the 2245 is 3/8" Reach and is the latest Autolite version for the M-151.
You mentioned the new (2245) Sparkplugs being longer. That is correct, as you are talking about the barrel of the spark plug. The M-715 requires a Water Proof Spark Plug with a shorter barrel as the 6 spark plugs are angled in pairs toward each other and require that shorter barrel in order to have room to install the wires. Installation of Long barrel water Proof Spark Plugs on the M-715 will result in the ends of the barrels almost touching and making it impossible to install the wires.
That is my M-715 story of the day. :wink:
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