Frank,
Interesting question. Here's how I think it should be analyzed. To a first
approximation, engine horsepower scales as displacement times rpm. That is,
a 400 ci engine at 2,000 rpm will have about the same horsepower output as a
200 ci engine at 4,000 rpm (but half the torque of course). In your case, if
you proportion the rpm scales for relative displacement between a 306 and a
331 engine, then the two curves should be very similar if not identical. For
example, take the HP curve for the 306 engine and divide the rpm scale by
306/331 = 0.924. Then the HP peak will shift down by about 8% and of course
will fall off faster too, which matches the behavior you describe. With the
rpm scales scaled as I describe, you are comparing the engines on an equal
volumetric throughput basis, so that for equal valve sizes, volumetric
efficiencies, etc., the engines should produce equal power.
Bob
Bob Palmer
rpalmer@ucsd.edu
rpalmerbob@adelphia.net
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