[DMVR] Bore vs. Stroke

[Ric Johnson]

At 09:39 PM 6/13/05, Karl wrote:
>All other things being equal, will there be an effect on Torque and/or HP
>if 2 engines of same displacement achieve this displacement by different
>combinations of Bore & Stroke?

This is by no means the definitive answer, but I'll take a stab at it based 
on my fuzzy memories...
In my experience generally the shorter stroke engine will develop more 
horsepower at a higher rpm at the expense of torque. An example of this is 
the early pre-S type Mini-Coopers which used two engines of nearly 
identical displacements; 997cc and 998cc. The original Mini-Coopers like my 
'62 had a 997cc BMC A-series engine that was basically just a stroked 850. 
After a couple of years that was replaced with a 998cc A-series which had a 
larger bore and shorter stroke, but essentially the same head and 
carburetion. The 998 would rev more freely and developed a bit more hp but 
didn't have quite the torque of the original 997. Another example, though 
not quite as clear due to different displacements, was the early Chevy 
small block Z-28 engine, which was basically a 327 with a 283 crank to get 
the displacement to 302 c.i., just under the Trans-Am 5 liter/305 c.i. 
limit. Again the engine would produce prodigious hp at high revs, but was 
pretty gutless in terms of low rpm torque.

Ric