>
>
> > Does this mean that if the bore is bigger than the stroke by a significant
> > amount it will rev it's nuts off.....:-)
>
> As I understand it the general rule (assuming the same displacement) is long
> stroke = good low end torque; short stroke = high revving horsepower. Of
> course a side benefit would be that the larger bore allows more room for
> valves.
>
Here's my attempt on the difference, based on what I remember reading from
my engines textbook:
With a long stroke, the pistons and rods have to move further per stroke
than on a short stroke engine. So at a given RPM they're going to be moving
faster. That means more stress on them at that given RPM, and that's why
they can't rev as high.
With a large bore, you have more surface area for the combustion to push
on, equating to increased hp, but it takes longer for the flame front to
move across the cylinder and there is greater possibility for distortions in
the flow. This causes problems for even and complete combustion, and means
the large bore engines aren't as efficient as small bore ones.
I'm sure there are other differences I have forgotten, especially since
what I wrote doesn't explain why a long stroke would provide better low end
torque.
Jeremy DuBois
Programmer/System Administrator
Thermalogic Corporation
'74 MGB, '76 Spit
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