horsepower, net and gross, was 71 440 power rating

["D. Dardalis" <dardal@xxxxxxxxxxxxxxx>]

At 09:42 PM 4/13/2002 -0600, you wrote:
>Should i not believe anything in that book now?!?!  Also what is 220hp net 
>mean?
Kevin:
This comes up often.  Gross power (or SAE gross) was an "imaginary" figure 
that the manufacturers used to sell cars back in the 60's.  Initially, it 
was defined as a method of measuring engine power and torque without 
accessories (including water pump), no air filter, no mufflers, etc.  But 
as the 60's came along, the horsepower wars made most manufacturers to 
claim gross ratings that were quite beyond the abilities of the engines, 
even as gross figures.  In some few cases, the power was under rated, in 
order to keep the insurance men happy, but that was quite rare.  So, 
ultimately, the gross rating means little to nothing.  The net power 
represents the power of the engine at the flywheel with the engine tested 
the way its installed on the car (all accessories, air cleaner, exhaust, 
etc).  Fortunately, Chrysler engines of the period had typically net 
ratings a bit closer to the gross than usual.  The 350 hp gross 440 of 
67-70 with dual exhaust will produce somewhere between 260-280 hp net, and 
the 375 hp gross about 310-330 net.  According to Chrysler numbers, the 71 
440 HP was rated net at 305 horsepower.  The single exhaust standard engine 
rating of 220 is reasonable, but with dual exhaust you should be able to 
raise it by 20 or 30 hp.  Remember, horsepower refers to upper rpm 
torque.  The low rpm torque of the standard engine will be stronger than 
the HP version.

Also, the minimum octane requirement of the fuel does not depend so much on 
whether the engine is an HP or not, it depends on the compression 
ratio.  If the HP and standard engine in 71 used the same ratio (as they 
did from 67-70) then the octane requirement should be the same.  In fact, 
an engine with a small cam and high compression ratio, may need the premium 
fuel more than a similar engine with a "bigger" cam.

D^2