The Ford Barn - View Single Post - What Defines Over-Revving The Model A's Engine

MikeK · 05-09-2020, 01:14 PM

The oil tray that feeds the dippers begins to suffer from 'windage' above 3200 rpm. That said, years ago modified A's raced with rod dippers in the 4-5000 rpm range.

Second point, even if you have a counter-weighted crank, with only three mains the weights are pretty far off-center from the actual rotational masses they attempt to counter. The offset opposing centripetal forces then bend the crank sections out of line in an RPM relationship that is exponential, not linear.

Third, an A has no front harmonic damper to prevent the severe 'ringing' shock waves that travel back and forth from front to rear along the crank. I wouldn't want to run all day at 3000+ rpm and heavy throttle unless you like swapping out broken cranks.

05-09-2020, 01:14 PM	#10
MikeK Senior Member Join Date: May 2010 Location: Windy City Posts: 2,919	Re: What Defines Over-Revving The Model A's Engine The oil tray that feeds the dippers begins to suffer from 'windage' above 3200 rpm. That said, years ago modified A's raced with rod dippers in the 4-5000 rpm range. Second point, even if you have a counter-weighted crank, with only three mains the weights are pretty far off-center from the actual rotational masses they attempt to counter. The offset opposing centripetal forces then bend the crank sections out of line in an RPM relationship that is exponential, not linear. Third, an A has no front harmonic damper to prevent the severe 'ringing' shock waves that travel back and forth from front to rear along the crank. I wouldn't want to run all day at 3000+ rpm and heavy throttle unless you like swapping out broken cranks.