6C 1750s, and fuel grades

[JHertzman@xxxxxxx]

In AD7-207 Keith Hyndes asked "for specs; power output, rpm, compression, etc.
for the 6C 1750 (circa early 1930's). Any idea on the fuel grade available
then?"

In AD7-209 Zamani Zambri gave a concise rundown on the types, with a few specs
on one of the hotter variants. 99% correct, but there are a couple of things
on which one could lose a barroom bet, e.g. "Although there are many models,
it seems that they differ only on the little details i.e. the testa fissa
models had fixed head/block (I think)". Proper caution, ZZ. 

The testa fissa cars (both 1500 and 1750) are not counted as 'production cars'
by Fusi, but are listed by him with the GP cars and "Sport Prototipi" and
other "vetture speciali". This is a pretty exclusive list; one 8C 2900 (the Le
Mans Berlinetta) made the list, but the Mille Miglia 2900s are just cars, as
are all of the 2300s. A few of the t.f.s were said to have been hastily
equipped with phony headnuts to fool the scrutineers at one "production car"
race. The fixed head was a bit more than a 'little detail'. 

One of the other "little details" was the number of camshafts; just over half
of the 1750s (1131 out of 2259, which really is 'JUST' over half) were single-
cam cars, a feature not shared with any later Alfa-built engine I can think of
until the V6, although there were single-cammers among the outsourced diesels.
The berlina bodies which graced most of the Turismos and many of the Gran
Turismos were Alfa's first venture into standard factory-built sedan bodies.
Between the engine types, bodytypes and performance figures it is no stretch
to say that a majority of the 1750s had power, speed, and style comparable to
a Model A Ford, although undoubtedly better roadholding. The widely printed
characterization of "100 hp, 100 mph" is not correct for any 1750 which was
offered for sale to the public. The fastest for-sale 1750 was appreciably
slower than a standard Giulietta Berlina. 

For the one model for which Zamani gives specifications his book says "Fuel
feed: 1 supercharger + twin carbs". The blown cars had single carburetors, the
unblown had single updraft carburetors, with two throats on some of the hotter
ones.

There are two major books on the 1750s, one, small, rare, out-of-print is by
Luigi Fusi and Peter Hull (in either Italian or English) but the definitive
one is "Alfa Romeo Tipo 6C 1500 1750 1900" by Angela Cherrett, an excellent
book which crams a lot of basic history about the company in with a sound and
exhaustive history of the model.

The tougher question Keith Hyndes asked was "Any idea on the fuel grade
available then?" I assume he means gas-station gas, and I don't know, but most
of the unblown 1750s ran a compression ratio of 5.5-1 rather than the 5-1
Zamani cites for the hotter blown cars. But for competition purposes alcohol
was extensively used as early as the turn of the century, when the World-
Record Gobron-Brillie was the first car to break 100 mph. There is a bit more
on fuels in Cherrett's book on the 2300 than in the 6C book; some of it (the
number of types of fuels and their names) comes from Alfa Romeo carburetors
jetting data, but the grade information all comes from a single source
Cherrett cites, "Appunti di Storia", written by Carlo Mariani and published by
Shell Italia in 1957. (If anybody has a copy, I would be interested in a
photocopy).

On the heavy use of alcohol, it is useful to remember that Italy (and most of
Europe) had no Texas, no offshore rigs in the North Sea, no Saudi Arabia, and
there was much interest in and economic justification for substitute fuels.
Fuels referred to in the jetting instructions include Dynamin, Dynamin 1,
Dynamin 2, Dynamin A, Esso, Standard 2 bis, Standard 3 bis, Elcosina, Elcosina
SC, and Elcosina Aviazione. Dynamin was a Shell brand, and the book gives two
formulas for Dynamin; one is ethyl alcohol 20%, benzol 30%, petrol 49%, castor
oil 1%, giving an octane rating of 95/100; the other, for track and circuit
races, is ethyl alcohol 44%, methyl alcohol 44%, aviation petrol 12%, and
castor oil 1% by weight, later replaced by "Shell Super Heavy" which was 90%
castor oil and 10% mineral oil; this gave an octane rating of 120/125. The
formula used in the 1932 Mille Miglia had the 20-30-49% proportions, but the
petrol component was qualified as "(special aromatic)". In later Mille Miglias
the Scuderia Ferrari ran the 2900s on another formula devised by the engineer,
Stefano Somazzi, who had formulated the Dynamins; 85% methanol, .55%
denaturant, .3-.4% water, and 14% free residues (sic).

How much lower the octane rating would have been for normal road use I cannot
say, but the above Dynamin formulas were used in blown 8C 2300s with 5.75-1
compression ratios standard and as high as 6.5-1 for the corsa; the unblown
1750 with 5.5-1 would have gotten by with far less, I would guess in the
seventies or low eighties. On the other hand, anyone who could afford to run
cars of this class could probably afford to fill them up on vodka.

Writing from a position of profound ignorance, I would be interested in any
better-informed input on the subject. Probably lots available in any reputable
university library if someone cares to dig, and perhaps some of the web-adroit
can beat even that. Anybody?

Cordially, 

John H.  

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End of alfa-digest V7 #218
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