Unfortunately I have not been able to participate directly in many "This is
wrong what should I do?" threads since I have gone on the digest so I end
up limiting my input to story telling and the occasional "sermon." Oh,
well. I still enjoy reading about everyone's experiences at least.
Lately there has been a discussion about how to fix an engine. It seems to
me that we are polarizing into the "duct tape and Motor Honey" faction and
the "Magnaflux and blueprint the heater valve" faction. There is a lot of
room between these poles and I believe that your approach should fit what
you plan to achieve, not some preconception of what constitutes a "real
overhaul."
For instance, I now have more disposable income than I did 25 years ago
when I bought my first sports car so I tend to buy more parts now than make
due with what I have. On the other hand, every dollar I spend on the A is
a buck my wife can't spend on something else ;-) so there is still a budget
to be considered. The key to successful work is knowledge of what to
expect when you are done. If you run a used car lot and have a taste for
plaid sports coats, then Bondo and STP are your best friends. They
definitely fulfill your needs of getting it to run quietly and look good
for the least amount of money. In fact my brother once bought a car with
rust repaired by Bondo over duct tape.
On the other hand if you are a well financed racing outfit and if you
break, you don't win and if you don't win, you don't get paid then by all
means buy 50 sets of connecting rods and mix and match for weights since
balancing is not allowed in your class.
For me, I fix what needs to be fixed and leave the rest alone. On a B
series MG engine, if you have 80k miles on it (especially a 3 bearing unit)
then it would benefit from new rod bearings and probably a rocker shaft.
The oil pump could stand replacement also. If the engine is basically
healthy there is no real advantage to going any further in my opinion and
this preventative maintenance will keep it going for years to come. If you
have to pull the motor, do the rings, mains, and cam bearings too. At 80k
you should not yet need a rebore but ridge reaming may be required. I just
did the A in this fashion and the crank journals cleaned up well with
crocus cloth and Plasti-gaged at the upper end of acceptable tolerance in
the manual with standard bearings. The ring gaps with standard rings were
also within tolerance. Comparing top to bottom diameters showed less than
.003 inch wear on the diameter (by inserting a ring and measuring the
change in gap.
The head is another story. If you do anything to the exhaust valves, put
in hardened seats. Other than that a pair of Chevy valve seals will keep
the oil out of the chambers for a few years at least. The head is
relatively easy to get off in any case so if you are going to save money,
do it here. Sucking oil thru the guides has never killed a car.
If I had to do it again, I would use a new oil pump. Pressure at idle is
low but acceptable. The A's motor now looks good, runs strong, and burned
less than a quart of oil in 2000 miles (Mobil 1 15W50).
Another thing to think about. When you have machine work, you assume it is
done correctly. I have heard many more stories of "everything new or
rebuilt/remachined" engines dying in 500 miles than I have of carefully
freshened motors biting it. Personally, I think that my lower than
expected idle oil pressure is at least partially due to the "universal" cam
bearings installed at a highly recommended machine shop. A worn grinding
wheel can destroy the stress relief radius on your crankshaft and you will
have a broken crank in a very short time. I had a BSA where the cylinder
was bored with a taper so if you set the ring gap at the bottom of the
cylinder it would jam solid at the top. You get the idea.
So to close. Whenever you work on a car, the correct approach is the one
that balances cost, and results to your satisfaction. The beauty of this
list is that if you mention your plans, you will definitely hear back all
of the good and bad points of your approach. However, they don't own your
car, you do.
Regards,
Bill Eastman
61 MGA in storage during the nicest November on record :-(
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