In <Pine.SOL.3.96.971119200949.3146A-100000@ux4.cso.uiuc.edu>, Der schwarze
Buccaneer wrote:
>I finally had some time to pull the head off today, and sure
>enough, the smaller of the two valves head, on #3, has a fairly large
>chunk out of it. I presume it's the exhaust valve. So, it looks like I
>need to, at the very least, replace that valve.
> Having said that, I shall now shamelessly ask for more! The
>pistons have a black crusty carbon like deposit sitting in the concavities
>(this isn't just a carbon layer, I mean chunks of stuff). Ought I to
>clean that crap off some how?
You can certainly decarbonise the tops of the pistons, an old and
noble British tradition. In many pre-war2 cars it was expected that
one would lift the lid and decarbonise every 10,000 miles or so. You
are cautioned to (1) use a very gentle tool, big gouges in aluminium
pistons are not recommended, and (2) Don't remove the stuff on about
the outer 1/4" if the piston diameter, closest to the cylinder. I
don't know why this is (group? How about it?) but the books always
say that. Perhaps it is to avoid gouging the cylinder wall, but also
could be something about messing with the seal of the piston and
cylinder.
> At least one of you recommended I have the head tanked. What is
>that, where do I have it done, and about what does it run?
Take the head to a reputable machine shop. I use a local speed shop,
not a chain. They can disassemble the head, tank it, install your new
valves and grind them in for a reasonable price if you carry the head
in. Shouldn't be more than $100. Note that you can't just buy a
valve and stick it in, it must be contoured to fit the seat. While
it's possible to do a 1920's style valve job in your garage, I prefer
to let the pros do a proper three-angle job.
> My plan is to just work on the head and let the rings go until
>next summer. Is it wise to rebuild the head now, or should I just replace
>the one broken valve and rebuild it with the engine?
Unless your valve seats are severely eroded, I'd just fix the busted
stuff for now. (1) MGB heads are severely prone to cracking, and I
wouldn't invest a whole lot in the head unless it is Magnafluxed to
check for cracks. (2) Consider that you can buy a rebuilt head off
the shelf with stainless exhaust valves and no-lead seats for about
$400. This is much less than you would pay if you got a parts kit and had a
machine shop do the work. Try British Parts Northwest, they advertise
in Hemming's.
>I'm thinking hard
>about one of the no lead valve kits, such as from VB. Is there any mail
>order house out there with cheaper prices?
See above comment. If you really want to roll your own, try Steve
at Northwest Import Parts (different outfit), also advertise in Hemming's.
He sells valves and guides and any competent machine shop can provide
no-lead seats.
A. B. Bonds
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