Re: What is a "reasonable" speed in a Model A for one to get "reasonable" engine life
With attention to detail a stock model a engine with the stock drive train will do 60 mph.Dilligent adherence to specification and proper assembly will yield the results Ford advertised.The problem arises when you want 'reasonable engine life..Ford engineering,Lawrence Sheldrick's engine team noted an issue with main bearing wear at high speed and felt a larger crankshaft journal would provide the stability needed to overcome the torsional vibration encountered.Mr Ford overruled them citing flywheel mass was capable of dealing with the issue.
Today,counterbalanced crankshaft and harmonic balancers counteract torsional vibration.At high rpm,the stock model a crankshaft vibrates like a tuning fork,flex has been estimated at .001 at the center main at high rpm (in excess of 2300 rpm). Ever wonder why a front crankshaft pulley cracks and fails? The same rule applies to the uncomfortable feeling you have when you drive the car too fast,its why 45 feels so good
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