> Tom said,
> V2 = V1 * cube root ( 1 + delta HP/ HP)

> Is that cube root (1+ (delta HP/HP))
> or ((1+delta HP)/HP)

Depends on whether DeltaHP =  HP2 - HP1 or the other way  about.

Easier to  avoid confusion this way:

V2/V1 = (HP2/HP1)^1/3

or

(V2/V1)^3 = HP2/HP1

The majority of the advertised HP increase for
the IO-360 (from 180 to 200 HP) would be due to
the compression increase. If the compression ratio
before was 8.0:1, then increasing to 10.5:1 would
raise the HP output (for the same air/fuel input)
to 194 HP.

see for example:
http://www.bgsoflex.com/crchange.html

The HP gain from porting is harder to predict.
Basically it depends on how bad the ports were
before modification. There might negligible gain
in power, but some improvement in smoothness by
making all four cylinders the same.

There might be 5-6 HP gain for "free" by simply
measuring the engine on a dyno. The LyCosaurus
specs for power output refer to the *minimum*
power output for an engine off the production line.
The average engine has a few HP more than the
worst engine.

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