Before the original "Keeping Track" came into being, Penton had a dealer newsletter called " Keep'em Winning ". In the No. 17, August 1972 issue, Ted Penton explains how all of the "A" engines had an 8 mm front motormount bolt, and that starting with the "B" engines the front bolt is 10 mm. I have checked all of my engines and found that Ted's statement holds true, as well it should as Ted was as deep into those engines as the factory boys. This might be the answer alot of guys have been looking for, how to tell and "A" engine from an "B" engine without tearing into it. Just check the size of the front motormount hole in the engine cases, 8mm "A", 10mm "B" or later.
Thanks, Paul. I'll check my cases and see what size bolt they take. This may be a simple way to finally nail down which is which.
Glenn
As in past discussion between "A" and "B" the ignition wire hole was changed, if it the slotted hole you know for sure it is a "B" engine, but through research ( I got one today) You can have a "B" engine with the little round wire hole. Better stick with the above mentioned checks.