Re: Spica head-to-manifold studs

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

In AD8-0163 Bruce Giller writes about studs:

"In a foolish attempt to have everything new on my GTV's re-worked head, I
removed (or tried anyway) all the studs, exhaust and intake.  Wes I. did all
the head work and the head came back missing 4 studs (out of 7) on the SPICA
intake side.  Turns out that he could not source them anywhere new.  These
studs are quite peculiar in that the pitch into the head is 1.25 (common
pitch) and 1.0 on the nut side!

 "Been thinking of just buying some DIN 8.8 bolts of the requisite length,
loping off the head, and threading some new 1.0 threads.  But I remember
trying this a few years back and I couldn't get my die to get started on the
bolt - the metal was far too tough.  The other idea was to have some new studs
made; inquired of some of my machinist acquaintances and they said that they
couldn't do it - too hard.

 "The last idea was to just buy some 1.25 pitch studs (of the requisite
length) on either end and use some 1.25 nuts.  Is there a sound reason why
Alfa went with the 1.0 pitch on the nut end of these studs????  Will the oil
pan fall off in a fit of solidarity if I use the incorrect pitched studs??"

 One of my unfinished projects (if that is not a tautology) is getting a
handle on Alfa's fasteners; I thought it might be both simpler (ha!) and far
more useful (yes!!) than understanding the paint numbering systems. I got far
enough into it to realize that it is a bigger task than I will ever master,
compounded by language problems (is some particular differentiation technical
and real or merely sloppy translation?) and typos (why do the part numbers in
the plate not correspond to the ones listed for that plate?).

 So what I can offer in Bruce's case are limited, partial answers.

 First, there is nothing peculiar about 8 x 1 x 8 x 1.25 mm thread
combinations on Alfa studs; they are ubiquitous.The 1.25 mm coarse thread
(ISO, JIS, and DIN Standard) is the normally fixed end in the usually alloy
part and the 1 mm fine thread (DIN Fine) takes the normally removable part,
a.k.a. 'the nut'. There are very few 8 x 1.25 mm nuts on an Alfa or in an Alfa
parts-pile - at my last count about a dozen, with four different part numbers,
on a 2000.

 Second, one of the remarkable (to me, anyhow) things about Alfa's 8 x 1 x 8 x
1.25 mm studs is the number of different lengths they come in, often differing
in length by one millimeter. In this thread combination just the basic "Euro"
2000 uses at least fourteen different studs in twelve lengths (23, 26, 32, 34,
36, 37, 38, 41, 42, 44, 49, 52, and 80 mm). The two duplicate lengths are 38
mm and 44 mm, where apparently the threaded lengths are different on each
pair. It would seem to cry out for rationalization- couldn't a 42 mm long stud
have done the job where a 41 is specified? - but at some level, perhaps from
their aero-engine background, some Alfa engineers would simply specify the
length needed. Not just on studs, either; bolts, nuts, washers seem to ignore
areas of possible cost-saving standardization. I doubt that Ford (or GM, or
Fiat) would have put up with it. Many, of course, will say nobody should.

 The 2000 Spica heads had seven studs for the intake manifold, as Bruce
mentioned- three 37 mm studs (2100.05194), two 44 mm studs (2100.05197) and
two 57 mm studs (2100.05202). The 37 mm 05194 is also used on the heads with
the carbureted intake manifold, along with a different 44mm (2100.10952) and
32 mm (2100.05192). The studs for the carbureted intake manifold all take the
same 8 x 1 mm nut (2120.15029) but the studs for the Spica intake manifold
take two different 8 x 1 mm nuts- five the same 2120.15029 as the Eurocar, but
two with a different part number, 2120.15053. Please don't ask me why. That is
one of those little Alfa quirks I would like to figure out someday.

 I don't know which four of Bruce's studs are missing, but I am surprised by
the "Turns out that he could not source them anywhere new" statement.  I would
certainly try an old-line Alfa dealer (like Spruell, for one) and then try a
few of the Eurosources, starting with Highwood and Hurtienne, and then try the
three US sources listed under "Metric Bolts" in the "Sources" appendix of
Carroll Smith's Nuts, Bolts, Fasteners (etc) Handbook. As a last resort short
of lopping the beads off bolts and threading the remainder, as Bruce had
tried, I would think about extending the threads on one of the next-longer
studs - if missing the 37 mm, trying to alter a 38, 41, or 42, and if missing
the 44 mm, trying to alter a 49 mm - or whatever was available in a slightly
longer 8 x 1 x 8 x 1.25 mm stud. But I would be very surprised if a proper
Alfa shop like my local one, Krause & England, didn't have in-stock a good
range of lengths of studs in this thread combination.

 The curse of working on older cars (one of the curses, anyway) is that
inevitably somebody has in the past disassembled things, throwing all nuts,
bolts, studs and washers in a coffeecan and later reassembled on an ad-hoc
basis- some washer under some nut, and in the worst case, if the thread don't
go, use a longer wrench. One of the joys of an Alfa of the Golden Age is that
many things were originally done with a remarkably fine level of
discrimination. For someone who is afflicted with an admiration for what these
cars were, a parts book can be as big a blessing as a shop-manual is. I don't
mean that I would never deviate from the original components, but I feel it is
good to know what they were when considering suggested alternatives, let alone
trying to correct the accretion of random alternatives which hacked-on old
cars are likely to contain. Which is why I started my (probably futile)
fasteners-list: I sure would like to understand Alfa's washers.

John H.

Raleigh, N.C.

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