Re: Spica attrition

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

In AD8-0067 Paul Irvine writes "I'm constantly amazed at how "delicate" people
imagine the SPICA system to be.  I see them fueling cars well into the "post
apocalyptic" decades after all the ECU's have been fried by the EMP's.
Seriously though - lax maintenance be damned, the SPICA pump is a soldier!
Stop worrying."

 I will cheerfully concede the point on fried ECUs, and I will also grant that
Spica pumps can, and obviously sometimes have, lasted for decades, as the last
ones were built over two decades ago. But delicate is as delicate does; I
inherited one Spica pump, of northern provenance, which has a broken
crankshaft; I wasn't there, but my understanding is that both the cogbelt and
the condensation ice in the logic section were stronger than the crank, which
was not strong enough to stall the engine's starter motor. The moisture
accumulation was probably helped by the rather casual logic-section
lubrication system, but I will leave that argument for others. I have also
heard of, but don't know the details of, a device known as "Francione's
Icebreaker" which was a patch ARI developed for severe-climate Spica pumps,
which suggests that ARI was more aware of the problem than mild-weather Milan
was. I assume that Paul's Antioch, CA address has few below-zero days in a
normal winter, but some parts of the USA are not so fortunate.

 Benign climate or not, I will take exception to the implication of the "lax
maintenance be damned" clause in his stop-worrying conclusion. I have had
experience with two Spica pumps which poured gasoline into the crankcase,which
is the most serious failure mode, as it can result in secondary damage to the
engine if you live by recommended oil change intervals; one was at less than
30,000 miles on a car which I know had been scrupulously maintained by the
book, and the other was the reason for sale of an apparently well-maintained
Sport Sedan which I bought with 58,000 miles on the odometer. Both may have
been odd cases of bad luck, but when/if one of my Spica project cars runs
again its injection pump is going to be the most pampered system on the car,
as the occasionally fatal flaw is wear in parts which are definitively NLA.

 I believe that the recent discussions of pump-fixes centering on relining
bores as are brake cylinders, or honing after building-up by plating,
underestimate the problem. Building an injection pump free from crankcase
dilution is roughly analogous to building an engine which has zero blowby
without using piston-rings. When roadgoing 300 SLs were new I heard horror
stories about crankcase dilution, like thousand-mile (or less) oil change
intervals, not a problem in race cars but unwelcome in road cars. My
understanding is that the Italian injection pumps were largely based on
pre-WW-II German diesel aircraft pumps which in turn were largely based on
pre-WW-I German diesel submarine engine pumps, both relatively low RPM
applications (2200 for the Junkers Jumo, I believe) in which the plungers
would be better lubricated by the diesel fuel-oil than the Spica's plungers
are by gasoline, and in which leak-by of the diesel fuel-oil would be less
critical for lubrication than leak-by of gasoline in an Alfa (or Mercedes)
engine. The Spica pump is a marvel both in the ingenuity of Raedelli's logic
section and in the precision of manufacture of the pumping section, but a
leak-by of a gallon of gas in a thousand miles would give a two-to-one ratio
of gas to oil washing bearings and bores in a three-thousand mile change
interval, which would not be good; the Spica pump might keep on running but
the engine might not.

 There is obviously a lot to be said for the Spica system, but service parts
availability isn't one of them; you can buy parts for Webers or Dellortos, or
vulnerable ECUs for Bosch systems, but in the end Spica attrition is going to
be unavoidable. Keep them running while you can, but it would be prudent to
not believe "lax maintenance be damned".

 Cheers

John H.

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