Postby Hasbeen » 07 Mar 2009 14:04
I don't believe in these long "running in" periods for modern, or
semi modern engines. Running in was a myth, perpetuated by car
makers, so car buyers could remind themselves, for a couple of
months, that they had a new car.
Many are the stories of new cars, in the 60/70s, being given a good
thrash, at valve bounce revs, at 2 or 3 thousand miles, by a service
adviser, to cure the excess oil consumption, caused by overly
gentle "running in" by careful owners. A good thrash would finally
bed the rings, or so the thinking went.
Once upon a time we had funny little men, usually with lung
problems, pouring molton white metal into all sorts of places in our
engines. Other men would use hand tools trying to make those areas
round. Thus we had main, big end, camshaft, & other such bearings
which were sort of round. These bearings required
considerable "running in", if local hot spots, & early failure were
to be avoided.
Then a very clever man invented the "thin wall bearing" & our modern
slipper bearings were born. It is a pity that the racing cars he had
built were not as good as his bearings. With round bearings, & the
thickness of the bearing metal now measured in microns, there is no
reason, or scope for running in.
So we are left with the valve gear, & the cylinders.
As underderdog says, with modern oils, the cam can be a problem, but
the "bedding in" process there is simple & quick.
Provided the cylinder walls are round, & straight, & no large ring
lip was left at the top of the bore, all the running in required for
rings, & pistons should be almosr finished by the time the cam is
done.
I lost count of the number of times I rebuilt racing engines, many
years ago. If you want to talk old tec engines, the Triumph TR3A
engine, that was in my Morgan +4, which did 5,000 miles racing,
would have to be close, as would most of the stuff I raced, back in
the 60s.
With all these race engines, after a rebuild, they were run very
smoothly, & gently, at about 2000RPM, until the engine oil was up to
60 deg C temperature, & then they went racing.
I used to bed new rings to the bore, with Braso metal polish, as the
chrome rings used at the time, were very hard, & took a lot of
bedding. Hepolite used to supply the compression ring, [yes only one
compression ring] with a cutting compound baked onto the rubbing
surface. As I did not like the idea of this stuff going into my oil,
I used to scrape it off, & do the braso thing.
Enjoy the pleasure of running in, your newly biult engine, if you
wish, but, if it has been done properly, it is ready to go, by the
tine the oil is hot.
Hasbeen
