Bill,
You have opened an extremely complicated topic. Let's start with re-bores. A
rebored engine will never be as good as the original bore. Why? When iron is
cast into an engine block, the material closest to the mold cools faster,
therefore the cyrstals are smaller, making a finer grain to the iron. As you
get further away from the mold, the iron cools slower, creating larger
crystals and a coarser grain. The finer grain makes a smoother, better
cylinder wall. That is why manufacturers try to machine as little as possible
from cylinder walls (also to save money, but here the two go together). When
you re-bore, you can never get as smooth a surface. This actually HELPS a
racing engine by retaining more oil but hurts longevity (but racers don't care
if the engine doesn't last 100,000 miles). The same is true when grinding the
crankshaft, but I believe not as critical.
Now to the oddity of Rootes engines. Each Rootes engine was "blueprinted"
when it was built at the factory, every component was measured and weighed and
then each engine was selectively fit. That is why you have different grade
bores, different grade bearings, etc. At the time, this was a radical approach
to engine assembly and produced an engine that was almost as good as a Rolls
Royce where all of the components were hand fitted.
Today, improvements in all aspects of manufacturing, from machining to casting
insure that each part conforms much more closely to the design then back in
the fifties and sixties (and probably seventies). In addition, improvements
in casting and machining insure much better alignment. So the final product
fits together MUCH better then even Rootes could do it 30+ years ago.
Finally, QC has come a long, long way. The introduction of Japanese (actually
American) quality control has insured that every engine is almost perfect when
it it goes into a car.
How would you rebuild a Rootes engine to match the reliability and longevity
of a modern one? Basically blue printing the engine and assuring that
everything was aligned (line bore the crank breaings, etc). I would measure
and weigh all of the new components, balance the crank/flywheel/clutch
assembly.
However, my experience has been that the Rootes engines last a long time, it
is the starter/fuel pump/water pump/etc. that need replacement far more often
then any of the main engine components.
Jan
"Barbara Blue" <the_blues@worldnet.att.net> wrote:
I had a conversation very much like this with my father about 30 years ago,
comparing the wearablilty of the engines of the '20s '30s to the engines of
the '70's. Few engines would go 50,000 miles without serious, perhaps
multiple overhauls. Pop was of the opinion that metalurgy had been good for
a very long time, but that lubrication had improved immensly over the past
twenty years. He marked the introduction of detergent oils as the turning
point in lubrication. Dad was a pretty good machine repairman (industrial
machines) and a good machinest, so I figured he knew what he was talking
about. Fast forward to today, and the oils we had back in the '70s do not
compare well, almost as bad as the comparison dad was making to the oils of
the 20s and 30s.
I also worked a few years with a guy that was involved in field testing and
developing Cummins Blue. This is an oil developed by Cummins Engines as an
extended drain oil for heavy Diesel use. He was in complete agreement with
pappy.
So I would say yes, you can probably see an extended bearing life compared
to the original. As far as I can tell, bearings are made pretty much of the
same way and with the same materials for the last 50 years. But I cannot
cite any specific data to back any of this. Any bearing experts or oil
experts out there?
Bill
Original Message -----
From: "William Lewis" <william.lewis@ucdmc.ucdavis.edu>
To: <alpines@autox.team.net>
Sent: Tuesday, March 06, 2001 8:16 PM
Subject: engine rebuild
> My understanding of why newer motors can go 200,000 plus miles (like my
> Jeep Cherokee) is in part that metallurgy has improved over the years.
> This includes better bearings, but also includes the realization that if
> rings wear, then using thicker rings will allow for a longer engine life.
> If any of this is true, does anyone know if the bearings, etc. that I put
> into my recent engine rebuild have benefited from any of the new
> technology. I doubt I will get 200,000 miles out of my Sunbeam motor, but
> 100,000 miles trouble free would be a dream.
> Bill (FrankenSeries II) Lewis
|