cooling fan HP, The Vandenberg Papers, etc.

["John Hertzman" <johnhertzman@domain.elided>]

In AD8-0474 Ed Prytherch asks "Is this 5-7HP for the fan a good number? I've
seen it in catalogs, but I've also seen 12 HP for headers."

Please pardon a disorganized answer, I am patching from a couple of aborted
(because potentially offensive) prior starts on remarks about the current
performance mods thread.

I have not followed the entire current Spica-vs-Weber discussion, but at least
part of one side of it comes from Scott Fisher, as here restated by Dana
Loomis: (Scott): "could it be that the Spica actually produces the same power
with a weaker cam that the Webers do with a stronger cam -- could the whole
point of putting Spica on the U.S. cars was to give them the same performance
as the European cars, AND meet smog laws?" (Dana): "Probably.  And here's the
scary part: if a box-stock US-model injected engine with weaker cams and
detuned timing makes about the same power as the stock Euro-spec carbed
engine, then shouldn't the injected engine be capable of making MORE power
than the stock carb version with a few very mild modifications?"

Yes, but - was this contrast (weaker cam/stronger cam) ever suggested? The
Spica was introduced in the USA in cars which were claimed to develop exactly
the same horsepower using exactly the same cams, the 105.02.03.200.01, which
were being used in the carbureted 1750 in Europe and elsewhere at that time.
Two years later with the 1971 MY the Weber 1750 gained the 105.48 cams
(without any claimed gains that I remember having seen, although there must
have been some) and a year after that, with the 2000, the US Spica version
received the weaker cams Scott and Dana referred to, the 105.20, which should
not be confused with the 105.02 of the 1750, while the Euro/elsewhere 2000
kept the 105.48 cams from the late Euro 1750. I don't believe it was ever
claimed that the Spica 2000 with the 105.20 cams produced the same power as
the carbureted 2000 with the 105.48 cams.

In AD8-0465 Norm Riffle wrote, re searches for more power:

"Most notable was possibly dave vandenburg who had a shop in the bay area and
belonged to ARA. sometime during the late 70's early 80's he authored "the
vandenburg papers" ,published in the overheard cams, which sought to answer
some of these questions via the dynamometer he had access to. this could be a
good place to start for someone wishing more out of his spica fueled spider.

"To my recollection the euro cams were about a 5 hp improvement over the stock
USA profile at the same 102 deg timing. this is enough to actually feel a
difference. and if your just beginning to make these kind of mods, it's great
to do something that actually makes a difference.

"Notable to me was the fact that removing the water pump mounted fan netted a
7 hp improvement - depending on the RPM.  i.e. with the stock fan there were
greater losses at higher RPM. 7 HP @ 7k RPM or thereabouts. an added benefit i
might add is that the engine SOUNDS much nicer without the motor trying to
force all that air about. I had a GTV at the time and added an electric fan
but found that with a freshly rotted radiator even in the bay area summertime,
it rarely came on while i was moving.

"there were other tests, the results of which are less memorable to me --
shankle headers, other cams, quadraflow...."

Not to quibble- Norm was writing from memory- it was Vandenberg, not
Vandenburg, and if it had been previously published in "Overheard Cams", the
ARA newsletter, that was not mentioned by the usually scrupulous AROC Tech
Editor Joe Benson when he wrote the introduction to the article when it was
printed in "Alfa Owner", the AROC newsletter, in February 1981. Vandenberg was
checking the improvements several variables offered against the 1976 Spica
engine, which was probably the most strangled version of any, and against the
1979 version, which was considerably better, certainly the best of the late
Spica engines. The article is interesting reading, at least in part because it
is a cautionary tale for those who want to pick up a bunch of horsepowers by
buying several improvements each of which are good for a five or ten
horsepower gain. It also offers an object-lesson on how extrapolated
inferences can gain weight in time; one hears about the 7 hp the fan consumes,
by Norm's recollection "7 HP @ 7k RPM or thereabouts", which is reasonable and
may be correct enough but Vandenberg stopped that chart at 5500
(coincidentally about as high as Alfa's rated peaks for the long-stroke
engine); he recorded six hp gains at 4500, 5000, and 5500, up from one hp at
3000 and 3500 and 4 hp at 4000. It could be the gains progressed to 7, 8, 10
at 7000, or it could be it flatlined, but the reading at 7000 is a guess
either way. Ditto the camshafts: to Norm's recollection the Euro cams were
about a 5 hp improvement over the stock USA profile, but Vandenberg had run
three cams- the 105.48 Euro cam, the 105.02 cam (all US 1750s and pre-1971
Euro 1750s, as well as some late earlier cars) and the 105.20 USA 2000 cams,
up to 5800 rpm, with Weber carburetion, not Spica. At 3000 and 5500 his 105.48
Euro cam was producing one more hp than both of the US cams (71, 70, 70 at
3000; 105, 104, 104 at 5500.) Above 5500 all three cams were on the downslope,
with the 105.02 (2000 FI) cam losing it faster than the other two- 104, 103,
100 at 5800, which is as high as he went. By his dyno numbers the 105.48 is
good, but not good for five horsepower.

The conclusion of the article was that the best combination of the variables
they tested for a normally aspirated 2-liter Alfa motor produced a 12 percent
increase in horsepower compared to the 1976 motor and a 6 percent increase
compared to the 1979 motor, and "This increase in power is small in both
comparisons, showing the efficiency of the stock Alfa motor to be relatively
high for the street". It is interesting reading, but not too encouraging for
those who want to buy useful gobs of added power. Worth cribbing a copy from
any friendly packrat who saved his Feb 1981 Alfa Owner, or whatever Overheard
Cams it appeared in.

I will also mention that Fusi publishes a number of comparative power-curve
charts which some may find worth looking at. On p.572, five variants on the
1570 cc engine, from the single downdraft 'normale' through the GTA; p.598 the
GTA and TZ2; p.602 six versions of the 1290 cc 105 engine; p.660 the '1750'
and '2000' engines, together with two sizes of the GT Am; p.734 the 1779 cc
Alfetta; p.786 the 1962 cc Alfetta; p.800 the 1357 cc and 1570 cc Giulietta
Nuova. Also, for peripheral interest, the Montreal on p.709, and four 33s (the
V8, not boxer) on p.650. The two Alfetta curves offer a nice comparison; with
the same cams both the 1779 and the 1962 cc engines peak with 140 hp SAE at
5500, but with very different torque curves, and with a steeper rise and
broader top on the larger engine.

Cheers

John H.

Raleigh, N.C.

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