<VV> Micrometers vs. Plastiguage
Mark Durham
62vair at gmail.com
Tue Apr 3 17:19:02 EDT 2012
Matt, to summarize, Bob. Is correct, but all you really need to know is
that plastiguage is made to give you the same clearances as a manual
measurement would give you with calibrated tools and a experienced
user. Mark Durham
Sent from my Windows Phone
From: BobHelt at aol.com
Sent: 4/3/2012 13:42
To: matthew_lockwood at hotmail.com; virtualvairs at corvair.org
Subject: Re: <VV> Micrometers vs. Plastiguage
Hi Matt,
I'd suggest that you be careful using the same specs for mic vs plastigage
measurements. The Shop Manuals all refer to making Plastigage measurements
and their specs refer to that method. When Plastigaging, you are measuring
the clearance of the crank journal to the bearing . That is the running
clearance. The SMs specs all are in the 0.001 to 0.003 inch range.
But by using micrometers to make these measurements you are measuring the
clearance on both sides of the journal and thus your clearance measurements
will be twice the specs for any bearing. You are measuring the jourmal
diameter to the bearing diameter. In addition, the Mics cause an increased
measurement error since you must use TWO different measuring devices that may
or may not be calibrated correctly. All that plus any human error in maiing
two measurements.
Regards,
Bob Helt
In a message dated 4/3/2012 9:25:12 A.M. US Mountain Standard Time,
matthew_lockwood at hotmail.com writes:
Wondering if the specs are the same for using a mic vs plastiguage. So,
if the green manual calls for a clearance range of .003-.006 on a crank
journal (from memory, I think thats right), using green plastiguage in lieu of
mics should suffice, correct?
Thanks,
Matt
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