Ron,
Cam bearings don't wear at the rate mains and connecting rod bearings
wear. One reason is that the cam rotates at a constant speed, and it's
half the RPM of the crankshaft. Another is that there is comparatively
more bearing surface on the cam bearings, so there is less pressure per
square inch than on the other bearings.
Did you have the shop clean the block? Most of the cleaning processes
will dissolve the cam bearings. Some do not, but one would want to check
that they were not damaged by the cleaning chemistry.
If the shop says the bearings are OK, though, and you selected the shop
because of good experiences by others and their recommendations, it would
seem that you could safely trust his judgment on this.
You can remove old and install new at home. It's careful work, and
requires a tool not found in most home shops, but it's not a complicated
job. Check Section A.17 in the manual. That tool pulls the new bearings
into place, each adapter being a precise fit for the bearing it is
pulling. The manual talks of reaming. This Spring, when I was
rebuilding an MGB engine, there were two types of cam bearing available.
One is made of a piece of metal wrapped round and keyed to itself, the
other was one-piece and round. The keyed type required reaming; the
one-piece did not require reaming.
If you had access to a lathe, you could make your own special tool
18G 124A with threaded rod and nuts if you could make the adapters. WIth
it you could easily pull out the old bearings and pull in the new ones.
Would I do it again myself? Probably not. This spring we did it in
the shop of a friend who has years and years of experience with engines.
Had he not offered, I would have had the shop that did boring, balancing,
etc, press them in for me.
Bob
On Tue, 25 Sep 2007 08:56:23 -0700 "Ron Fine" <RonFineEsq@earthlink.net>
writes:
> I purchased a new cam (stock) and gave the machine shop that is
> machining my
> MGB engine a set of new cam bearings to install. Now the machinist
> is telling
> me I don't need new cam bearings. I just assumed that if I was
> installing a
> new cam I should replace the bearings. Should I accept his advise
> or find a
> new machine shop to install them? Do I need any special tools to
> install them
> at home?
> Ron Fine
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