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Originally Posted by MN Stumpjumper
How about RPM's, Anybody run a tach? What is a "safe" RPM range,with a stock motor?
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SAE defines "overspeeding an engine" as operating it at speeds in excess of the point where peak power is produced.
The stock Model A engine produces its peak HP at 2200 rpm. In the case of my '28, with stock 4.50x21 tires and 3.78 rear, that should have me going along at 53 mph.
Theoretically, one should be able to drive at 2200 rpm "forever" w/o doing major damage to the engine.
The "babbit-pounding" Chevy six usually had its HP rated at 3200 to 3600 RPM, but then the six doesn't have the same inherent balance issues as a four (or V-8) with a single-plane crank.
Lugging isn't good for any engine, especially a "splasher" with expensive poured bearings.