I had a misfortune which had all the makings of a disaster, but some good luck
and help from a friend converted it to a mere inconvenience.
Our 100M's 50th birthay was October 23rd past. Coincidentally, that weekend
was the VSCCA Nutmeg fall ralley, and we packed up Emily for the 300-mile
round trip to Storrs, Ct.. On Saturday, two minutes into the ralley, we blew a
frost plug which had been oozing a while, and replaced it without any trouble.
Fifty miles later, and in the wilds of eastern Connecticut twenty minutes from
every sign of civilization, we experienced steam rising from the underside of
the engine compartment. On exiting we saw frothing oil puking out of the
breather. Limping on, the situation worsened. Water was rapidly disappearing
from the radiator.I figured water was getting into the oil and feared we had
blown the head or head gasket. A good samaritan stopped to help us with an oil
change and afer topping off with oil we tried to limp back to a repair
station, but to no avail. The new oil was quickly polluted with water and the
same steaming froth was pouring out the breather tube.
Sadly for Emily, she spent her fiftieth birthday in a dairy barn and we
hitched back to the hotel with another rallier, and joined the banquet in time
for a few drinks, albeit with laments that the birthday girl under the
weather. Too much cake and cookies, or whatever.
In the following week we called everyone we could think of and braced for the
worst case scenario, a cracked head or possibly an internal fizzure in the
block, rare but not unheard of. What puzzled me, though, was that even in the
work situation with poor lubrication, the engine ran smoothly and idled
without hesitation. What puzzled me more is that we had put on a Welch racing
head, hardened studs, and the Welch gasket, and were getting no weepage out
the side.
We arranged a tow back to civilization and braced for bad news. Fortunately
for me, a friend and Healey Lister, Mark Goodman (BJ8 phase II) suggested I
try pressurizing the engine before tearing it down. He lent me a regulated
tank of helium and an ultrasonic testing unit sold by his company to detect
industrial leaks through gas turbulence. We plugged off the lower radiator
hose and introduced gas into the engine through the thermostat housing. After
charging 25-30#, we got a rapid fall-off and quickly located the turbulence
coming from the forward part of the head somewhere between valve springs and
the #2 rocker post. We disconnected the copper oiling tube and still had the
leaking, so this confirmed a pressure breach in the head's top plane. Using
the sonic wand, we were able to isolate the leak to the base of the rocker
post. Further testing showed the #2 cylinder valve positions did not alter the
leakage rate.
With higher pressure, it became very evident the breach was emanating from the
#2 right stud securing the rocker assembly to the DW head we had put on
earlier this summer. After removing the rockers, we found the stud was only
finger tight. A little pipe dope and tightening completely eliminated the
pressure leak.
I urge anyone who has installed a DW aluminum head to profit from my
not-so-disasterous misfortune. If you experience water contamination in the
oil with a Welch head, it is well to bear in mind that the coarse-thread studs
are inserted into bores which have no bottom, but go directly into the jacket.
This I think is by design, as the aluminum would stress-crack if a steel stud
were bottomed out in the hole. If this ever happens to you, pressure-testing
is a good alternative to tearing the top end down. Indeed, if we had pulled
the head we'd have gotten into an expensive exercise in futility: not finding
any evidence of leakage in the gasket, we'd have suspected an internal crack
in the block, and after dismantling the engine would have found nothing.
My thanks to everyone who coached on this -- Mark Goodman, of course, but also
to Davd Nock, David Ward and Jeremy Welch, as well as others. I've learned a
lot, and have been happy to enjoy another few rides with Emily before the
weather crashed this weekend. The Welch head is none the worse for wear, and
I'm relieved that Mark's disagnostics paid off.
Emily's winter plans include a little cosmetic surgery and a trip to the paint
booth. She's already making plans for the next fifty years.
Allen Miller
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