Crankshaft oilway plugs (again)

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

In AD8-0863 Modelle in Somers Point, prompted by some remarks in Kartalamakis'
book, raises a question about tapping the crank to receive threaded oilway
plugs to replace the aluminum ones which sometimes fall out, and are then
blamed for low oil pressures and the consequences thereof.

This and related topics have been covered at various times on the digest, one
of the more protracted and interesting threads being in AD5-49, 50, 60, 93,
94, 96, 98, 99, and 105, and restarted in AD5-203, 207, 211, 212, 213, and
214. There was a later interesting post by Chris Brown in AD7-042 (and
undoubtedly many, many others). Participants at various points included Jack
Hagerty, Chris Boles, Fred Di Matteo, and an anonymous oldtimer who had worked
on engine preparation for Alfa's first factory racing efforts in the USA at
Sebring. I excerpted the oldtimer's letters and also a Stewart Sandeman
article in 'Alfa Owner' which had drawn heavily on a prior discussion by Dave
Vehger and Gary Valant, so there was a broad assortment of the wisdom of the
ages as well as current thought. Too much there for me to repeat fairly; look
them up, if so inclined.

The primary problem with tapping the oilways was tap breakage, particularly in
nitrided cranks, (which came in with the production 2000, although used
earlier on prepared engines) followed immediately by the problem of getting
broken taps out. The solution which had been used in the fifties by
'preparatori' who did nitrided Giulietta cranks for builders like Conrero was
to bellmouth the oilways with a Dremel-like tool or die-grinder to penetrate
the nitrided surface in anticipation of the tapping. (Very thorough post-op
cleaning highly recommended.) The use of threaded brass plugs, soft enough to
be staked, rather than hardened Allen-head set-screws, was discussed, and
tapered brass plugs were mentioned. Fred mentioned successfully using the
original-type aluminum plugs, prechilled and inserted in a warmed crank and
staked, which avoids adding abrasives and thread-shavings. Chris Brown dealt
convincingly with drill sizes, tap sizes, and plug threads. And there have
been occasional contrarian opinions that dropped crankplugs are not really a
problem.

HTH, YMMV, ETC

John H.
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