bhp and ign timing

[Jay Negrin <jmnegrin@domain.elided>]

Earlier this week (please excuse if this has been covered already) Brian
Shorey responded to the question of ignition timing and horsepower measurement
this way:

<snip>
>> Can anyone tell me why Alfa would publish a timing spec that was so
totally out of kilter? Was 40 degrees BTDC a reasonable timing setting in 1966,
and if so, why?<<

"perhaps the octane of the fuel was higher in the 60's, allowing more
advanced timing and higher hp?"

>> P.S.: I've always heard that horsepower numbers from the sixties were
totally bogus. The dyno boys told me about Mustang club members who left the dyno
disheartened after finding that their "390 h.p." big block engines only
put out a real 220-230 h.p.<<

"i heard that all of the american hp figures were derived from running motors
on dynos with no accessories bolted on them.  while i don't think that would
account for 150 hp, it would certainly explain some of the difference
between quoted vs actual hp."

First, on the ignition timing; could that be the total degrees of the adavnce,
mechanical plus static.  Number is quite close to what I familiar with in
other cars.

Second, bhp determinations; in the early 1970s (1972, I think) the USofA went
from measuring horsepower using the SAE gross, to SAE net method.  Both are
dyno generated, but the net value measures the hp as the motor is typically
installed in the car.  You know, with such amenities as air filter, water pump
AND radiator, generator/alternator, REAL exhaust system, AC compressor, air
injector for smog control, power steering pump, etc.  Also, they didn't diddle
with the ignition timing for max power at various rpm.

Remember, too that in 192 the US started including oxides of nitrogen
standards for smog control.  Lowering compression ratios helped quench NOx, as
well as horsepower.  e.g. My dad had a 1970 Dodge with 318 cid V8 rated at 230
gross bhp.  He bought the same car and motor two years later, with only 180
net bhp.  

HP readings from the mid 60's could also have had a bit of Hollywood in them,
for advertising purposes.  That changed when the insurance companies started
surcharging for "sports" models.  The HP numbers went down, for insurance
purposes, rather than up, for a corporate ego boost.

Enough of your time.  
Ciao
Jay Negrin

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