Plain bearing material

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In #101 Bruce Giller comments / asks:

        "Whilst rebuilding my 2 L engine, my local Alfa mech. said that
I should
handle the main and big-end rod bearing shells with care.  I shouldn't
put my fingers on the inside surface of the shell least I make a scratch

or get a fingerprint on them.  Since I have to get the Plastigage off
the crank and the bearing, I do have to rub some WD40 soaked paper towel

on the bearing.

        "The material is easy to scratch and some of the bearing top
surface
does comes off on the paper towel.  The material reminds me of a babbitt

bearing.  Are they related?  Just how careful do I have to be with them
(other than keeping everything clean)?"

********

Personally I feel your mechanic is being more than a bit fussy. Might he
possibly be trying to say, "You should bring the car to me. I am the
expert."

Quite frankly I gently scratch off the Plastigage with my fingernail,
making sure none drops down the oil hole. Shell bearings come with a
light coating of (?) and assume your mechanic feels this should not be
disturbed.

Checking the bearing clearance is obviously more important than trying
not to 'disturb' the bearing surface.

While this wasn't part of the question, like you I try to keep all
bearing surfaces as clean as possible. I generally blow everything off
before buttoning up the crank and rod bearings. I also use a good dollop
of STP on the bearing surfaces applied with a clean brush. And yes, I
carefully check that there are no bristles left on the surfaces. I feel
the STP will stick in there until the oil pressure is sufficiently built
up before starting for the first time.

Unless you and other engine builders out there religiously change oil
every 3k miles, same with air filters, never let the engine sit for more
than a week at most without starting and driving for 30 miles or so,
never let the engine idle for more than 30 seconds at a timethose
bearings are going to see a lot worse in their lifetime than a few thumb
prints and very minor surface scratches.

Biba
Irwindale, CA USA

I double checked your spelling of Plastigage. You are correct! However,
shouldn't it really be spelled Plastic-Gauge? (The u in Gauge being more
important than the c in Plastic, methinks).

John H.? And, yes, I'm aware a company can call / spell / capitalize /
punctuate their name or the name of their products any way they darn
well please (De Dion, Alfa Romeo)...but why not add the u? The product,
after all, is a (very clever and helpful) gauge (not gage) for measuring
bearing clearances.

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