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Big Bore vs Big Stroke?
Posted: Mon Jan 05, 2015 6:39 pm
by Maverick
I always thought the 4.5" stroke in my Hudson Twin H was responsible for its big-time torque. Well, it was, but a big bore would have done just as well or even better if a bigger bore had been filled with bigger valves. Learn something every day ...
http://rehermorrison.com/tech-talk-53-b ... is-better/
Re: Big Bore vs Big Stroke?
Posted: Sun Jan 11, 2015 8:41 am
by Noisy Cricket
Not necessarily... the fun part is, if you have the same displacement but a longer stroke, the air has further to move to fill the cylinder because the distance to the farthest reaches of the chamber are longer. This means that the velocity past the valve has to be higher, which changes the way the port works, and generally speaking more peak velocity means more cylidner filling because the port is moving faster. Moving faster means more inertia to cram air in at the end of the intake stroke whenthe piston is coming up while the intake valve is still open.
So longer stroke CAN make more torque but it's not because of more leverage, it's because intake ports and valves are rarely optimized...