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July 22, 2003
Don,
Re the crack, there are many al. alloys which are not weldable, but I have
no idea about this one. In any case, a typical good welding-repair practice
for large and relatively fragile castings such as this is to pre-heat the
whole bare casting (in an oven) and keep covered with thermal blankets as
much as possible during the weld time to minimise distortion. Without this,
even if the bell housing IS weldable, one of the dangers is that you might
just cause the crack to propagate further by attempting to weld in situ and
thus cause more damage.
My recommendation is that you "stop-drill" at each end of the crack. This
may sound crazy, but it isn't. The theory is that the drilled holes actually
reduce the local "stress-riser" points - maybe there are some good
metallurgists/stressmen out there who can explain it better than I can. It
is a common crack arrester on many aircrfaft structural components and
al.alloy or magnesium castings.
Anyway, ......... I suggest you drill right through the casting,
perpendicular to the face, with a 1/16" drill minimum, or up to twice the
crack width. Use a vacuum cleaner with a small nozzle to catch all the swarf
as you go and not let it go inside the bell housing. After drilling, just
SLIGHTLY countersink the drilled hole to deburr and break the sharp edge. Of
course it would be nice to treat the inside of the hole the same way too,
but I don't imagine you are about to take the engine & gearbox out just to
do that!
So for what that's worth.... If it were MY car, that's what I'd do (is that
the real test?)
Any comments from real experts out there?
Hope this may help.
Rgds., Tony P.
"anthony pooley" < tpooley@... > 23614
Posted on July 22, 2003 11:04 AM
Posted to category(s) Engine (external) | Engine (internal) | Ignition System | Transmission | Tuning | US States | Wheels
