OK, OK, can't hold back any longer, I have to throw in my $.02:

The formulas in question probably mean very little, if nothing.  They
are probably true for a given engine+car combination and with a very
consistent driver behind the wheel (and the pedal, clutch, stick..).

The fact is, pure number of horsies means nothing more than a
conversation item.  You need to supply at least the rpm it occurs at.
Even more important is HOW the horsepower changes at every rpm -- you
need a horsepower output vs engine rpm graph.  And, remember, this
mostly means you can haul that much mass with the engine up a hill.
The real measure of acceleration is how the torque is distributed
across the rpm spectrum -- somebody on this list recently put it very
well: horsepower sells cars, torque wins races.

Back to the original question:  to determine if you have improved the
engine horsepower output (at least qualitatively), one simple
experiment can be done:  go to one hill that you remember the bus
could not climb on 4th gear (or 3rd) by a narrow margin.  If it can
climb up the same hill (loaded the same way) on 4th (3th) after the
engine rebuild/modification, then you definitely have improved engine
horsepower output -- at least at those rpms :-)

Cetin

BBTSQP8@baplaza.bell-atl.com writes:
 > 
 >      I LOVE IT!! With these formulas, we can always blame the engine, not
 >      the driver for slow 1/4 mile times. For example,a driver who normally
 >      runs a 12.00 1/4 mile misses a shift point, and records a slower 14.00
 >      second time. Driver error-NO WAY!! What really happened was the engine
 >      experienced a sudden and unexpected decrease in horsepower! :)