I have a 77 MGB I am restoring. I have rebuilt the suspension, brakes,
electrical, body, repaint, top, etc. I was advised to consider rebuilding
the engine (112k miles) next, but the oil pressure is good (50-70 pounds)
There's the key. If the oil pressure is still at 50 to 70 PSI, you
are probably still thousands of miles away from a rebuild.
I am looking for input from folks who have had experience with high
mileage, reasonably maintained MGB's and whether a rebuild is eminently
needed. Since I have done all the work on the rest of the car, I would
likely be the one to rebuild the engine.
I've got 147,000 miles on The Green Car, and I could probably just
maintain it to 200,000 miles with nothing more serious than a head
gasket replacement. Almost all B series engines tend to develop
a "weep" of coolant from between the two middle spark plugs. Keep
an eye on that; mine is finally bad enough that I think I'll probably
have to replace the gasket this spring, because I'm not sure it would
last through a hot California summer.
It's common for MGBs, when fanatically maintained, to make it to
200k miles before needing rings, valves, and bearings. The factory
design goal for the B Series engine was 100k miles, in the 1950s;
with really agressive maintenance and modern lubricants, twice the
design goal isn't out of line.
One of the most compelling reasons to rebuild an engine "early" on
an MGB, or on any old car, is to replace the gaskets and seals with
new components. That is, while the metal components are probably
satisfactory (certainly judging from your 50-70 psi figure on the
oil pressure gauge), your engine is full of 15-year-old pieces of
paper, rubber, and cork. I'm often tempted to pull the engine from
the green car, clean it inside and out, and replace all the gaskets
and seals if only so I can switch to synthetic oil and not worry
about having it pour out of the existing crevices. But there's so
much work involved in that that I might as well wait and do the
crank, and put in a new cam and lifters, and, and, and... Shipwright's
disease strikes again, so I live with my 50 to 55 psi of oil pressure,
keep the oil topped up, and plan to go another year or so.
One piece of advice that's becoming apparent from my own research and
also from a conversation in the wheeltowheel list is that you shouldn't
put too heavy a grade of oil in the car, particularly if you have an
oil cooler in it. You actually want the lightest viscosity you can
get that is compatible with your temperature range; a high-viscosity
oil in cooler temperatures will not as easily form a film between the
metal surfaces in your engine, and premature wear can result. I probably
shouldn't be running 20W-50 in my car in the winter, even a California
winter, which is why I start thinking about synthetic oils, which is why
I start thinking about the $16 conversion gasket set, which is when I
realize that it's a two- to three-week job to pull, disassemble, clean,
and reassemble an engine if you're working nights and weekends.
For the record, if you do all the work yourself, you can do an MGB
engine rebuild for a minimum of about $700, assuming you don't need
much machine work (but if you don't need much machine work, you
probably don't need an engine rebuild). That'd be all the gaskets,
seals, bearings, timing chain, cam and lifters, and minimal truing
of components as well as jet-washing or hot-tanking the block and
head. If you want special things, or if you need additional work,
the price of course will go up as high as you want it to go, and
it would probably be best to count on having at least a thousand
dollars to do the job right; you might need new rods, pistons,
valves, or other more expensive components. And of course if you
plan to improve the performance, well, how fast can you afford to go?
--
"Some people put their hands in the dishes the moment they have sat
down. Wolves do that." -- Desiderius Erasmus
Scott Fisher/sfisher@wsl.pa.dec.com/DEC Western Software Labs/Palo Alto, CA
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