<VV> Micrometers vs. Plastiguage

[BobHelt at aol.com]

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