I have driven all my conversions in a "spirited" fashion, & have never seen
a cracked bell housing. I have never seen a cracked bell housing for sale,
or heard of anyone else with a cracked bell housing. I would suspect some
sort of accident in its earlier life- car impact or engine dropped.
I have done some cutting & drilling on these bell housings & have never seen
evidence of any heat treating.
Jim Stuart
-----Original Message-----
From: owner-mgb-v8@autox.team.net [mailto:owner-mgb-v8@autox.team.net]On
Behalf Of james
Sent: Saturday, March 15, 2003 10:52 PM
To: James J.; v8
Subject: Re: Factory 4-sp bellhousing
Thanks James,
I hadn't ever thought about the heat treating aspect, but I'd be surprised
if a part like this had been treated in the beginning.
I can't honestly say that the bellhousing wasn't cracked before hand, but
I'm 90% positive that I would have noticed the first time I put the car
together. I look forward to hearing the advice of some of the others on the
list that have been using these parts for many years. At this point I'm not
worried about having it fixed, but I'd like to know if I should expect it to
happen again. If I had to guess I'd say that this thing was pretty beat by
its POs. The guts of the engine looked like it had lead a really hard life
and so it wouldn't surprise me if there had been some damage to the
bellhousing too.
James Nazarian
71B Tourer
71BGT V8
85 Dodge Ram
----- Original Message -----
From: James J. <m1garand@speakeasy.net>
To: v8 <mgb-v8@autox.team.net>
Sent: Saturday, March 15, 2003 3:10 PM
Subject: Re: Factory 4-sp bellhousing
> James,
> One thing we should find out is if the bellhousing was ever
> heat-treated for strength. I don't know if the OEM units were or
> weren't. Regardless, the temperatures involved in welding aluminum will
> kill the heat-treating in the HAZ (heat affected zone). And because of
> it's higher thermal conductivity, the HAZ in an aluminum casting will be
> considerably larger than in a ferrous material. This is why aluminum
> welds are considerably weaker than a heat-treated parent material (T6,
> etc.). If anyone in the group knows if the bellhousings were
> heat-treated at the factory, please let us know.
> To your original question, I'd just make sure that you take it to a
> competent weldor and ask if he pre-heats the casting prior to welding
> and uses a back-purge. If he says 'no', then turn around and walk out.
> If he says 'yes', he's a keeper, and will probably know what kind of
> filler to use (or rather what filler works best for him).
> You can get away without preheating aluminum if its small stuff like
> plate, and thin-wall tube, but on big, load-bearing castings and
> forgings, you want to make sure the whole piece is up to temp before
> welding, or else you run the risk of warpage and more cracking when the
> HAZ cools.
>
> james wrote:
>
> >Has anyone ever cracked a factory 4 speed bellhousing? I was starting to
put
> >my engine back into the car today, and when it came time to bolt the
> >bellhousing back to the engine, I got about half way done when I noticed
that
> >it was cracked. The thin area below the clutch lever hole is completely
> >broken through on the transmission end. There is another crack, tracing
> >around the transmission area from the linkage hole up to about the middle
of
> >the bellhousing. The cracks are not on the machined parts of the
bellhousing
> >but where the transmission mounting area joins the main casting that
covers
> >the clutch.
> >
> >I'm not sure when this happened but I have two guesses. First, and least
> >likely IMO, is that it was cracked by the shock of the engine destroying
> >itself while cruising at 4500 RPM on the highway. Second, and more
likely
> >IMO, was that it was the shock of driving hard with the Buick 4speed and
a
> >3.93 rear end although if this were the problem I expect that there would
be
> >more accounts of failures. Any ideas?
> >
> >I'm going to have it welded back up and have the clutch linkage area
filled in
> >as well, I will then drill a hole for my flex lines to pass through. I
intend
> >to have it professionally welded since I don't have a lot of experience
> >welding Al, but does anyone know what alloy of rod to use to reweld it?
///
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