Hi Mauricio and erudite listers,
>I just finished the complete restoration of my 42 MB engine. I don't
>know how to "break in" the engine as I imagine modern oils are
different
>and the procedure today may be different.
>
I think this is just a matter of standard practice, certainly modern
oils and the engines they are designed for are very different things.
>As I understand from old manuals, the crankscase was filled at the
>factory with oil of the proper viscosity for the "break-in" period.
>After 500 miles that oil was drained and replaced with engine oil of
the
>viscosity recommended in the manuals' Lubrication section.
>
When these engines were made there was just SAE 10 for arctic use, SAE
30 for all temperate climates and SAE 40 for the tropics. The point of
changing the oil at 500 miles was to remove the heavy contamination of
the oil because of "Break-in" and the comparatively poor filtration
system fitted at the time.
I would suggest a good SAE30, which is what it was designed for,
preferably to the current MIL 2104D spec. In '42 the allied armies
changed to a "Heavy-Duty" SAE 30 oil, for heavy duty read "detergent".
Instructions were issued to warn about possible oil-way clogging in well
used engines that may have sludge formation and the need for flushing,
this doesn't apply to a re-built and clean engine.
>Also, during the "break in" period it was suggested not to drive faster
>than 45 mph for the first 250 miles and then slightly higher until a
>minimum of 1000 miles had been traveled.
>
The essence of break-in is to settle all the new bearing surfaces
together and the standard rules are to lightly load the engine by
neither letting it labour in a high gear or use high revs. The key is
to steadily increase the load giving it short periods of heavier work as
the miles build up, the first 100 miles are the most critical where it
should be treated most carefully.
Having said all that I doubt very much if any form of break-in was
followed in war-time, and how would you do this in say a tank anyway ?
>My questions are:
>
>1.-Do I need to use different oil during the first 500 miles? If so,
>what kind?
>
Not really.
>2.-What should be the proper viscosity to use today? My mechanic
>suggests using SAE W40 but I think is to heavy for a new engine. I do
>intend to use the jeep on heavy roads.
>
SAE 30
>3.-Can I use detergent oils?
>
Yes, preferably.
>4.-Is it useful or recommended to add to my first oil one can of these
>new products such as "motorcote" that suposedly reduce the friction in
>any engine for like 80K miles? (as seen on TV...)
>
If these things actually do remove all friction as claimed the engine
would never bed in at all.
>5.-What is a safe "break-in" period? 1000 miles or more? Is the
>procedure described above correct for my engine? If not what shoud it
>be?
>
1K miles is the classic break-in distance however this doesn't mean you
should drive very carefully for 999 miles and then give it everything at
1K, rather that by 1000 miles you should be using the full range of
engine performance having steadily built up to it.
Note that most piston aero engines are required to be loaded from the
outset, indeed there are warnings about not idling them for more than
five minutes as it glazes the bores and its not possible to take off
with say ¼ throttle and half revs !
My 2 ¢ (1.2p).
Regards,
Richard
(Southampton UK)
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