sanborn Senior Member Feb 26, 2014 #1 We are finally getting to assembling the flathead engine. What spark plug plug should I use? The heads take a 3/4" plug, 14MM, the compression ratio will be 9.35 to 1.
We are finally getting to assembling the flathead engine. What spark plug plug should I use? The heads take a 3/4" plug, 14MM, the compression ratio will be 9.35 to 1.
flat-v8 Well-known member Feb 27, 2014 #2 I have Autolite 437 in mine, it is a little hotter plug than standard 216
