TM>Bill Eastman writes:
TM>> Replacing the rod bearings is not that tough. Maybe we should start
TM>> thinking about them as 50,000 mile items and just replacing them as a
TM>> matter of course. Expecially when you consider the havoc raised at the to
TM>> end of the engine with low oil pressure and the cost of an MGA crankshaft
TM>> nowadays.
TM>Coincidentally, amidst the frolic of disassembling my spare 'B motor -
TM>the absolute first time I've cracked an engine open - I noticed a very
TM>similar comment in the Haynes manual. They suggest doing rod bearings
TM>at 30k and main bearings at 50k. You all can go read it for yourselves.
TM>Since I'm a newbie at engine rebuilding, let me ask a newbie question.
TM>It looks as though this block will need to be bored to 0.020 over. Does
TM>this automatically necessitate new, oversized pistons?
This kind of thing is new to me also, but the 1971 1275 I got had been
sitting for 16 yrs, and one of the pistons had seized up. I removed the
piston with a grenade, and proceded to have a friend of mine who is a
machinest, check it out for me. After measureing all of cylinders, and
the crank, the worst dimension was .0004 out of factory spec,( #1 cyl, I
was suprised, the motor supposedly "ran fine" with 86k on it, so I
figured it would be pretty bad) Apparently, internal maint. had been
done already. So in go new Standard, Pistons, Rod bearings, and Main
Bearings. I was recomended to CLEAN the cylinders with a hone (not
removing much material ) and replacing the bearings ( cleaning crank
with a little crocus cloth ).
So my guess is, that the engineers did their job, and set up the engine
so that the wear points could be replaced, when needed, with out having
to relpace the BIG items such as the block,crank, and probably the head
too. The materials used put the majority of the wear on the "wear
points" ( bearings and rings ), so if you maintain these parts, and
replace them BEFORE they get really bad, you'll save yourself a lot of
aggrevation, and MONEY.
Maint. mans $.02
71 midget
If anyone is interested I'll keep you up on this minor refresh job.
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þ SLMR 2.1a þ john.kahoon@pcohio.com
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