67SS509

iTrader: (25)

The method I use for measuring main bearing and rod clearances is torque the main or rod caps with the bearings installed. Then I measure the crank journals with a micrometer and use it to set my bore guage to zero. The difference from zero (example .0022") is the oil clearance. Assuming technique is without errors how accurate should this be?
+ or - .0001"? .005"? .001"? What's everyones opinion on this?

If I take the ID measurements of the main bores and the rod bores, substract the crank journals OD and then substract the published bearing thickness this never comes close to the actual oil clearance measurements. Does this method ever work?

racer7088

You should be accurate to a few ten thousandths if you know how to use the mics.

67SS509

iTrader: (25)

I feel like I have the usage of the mic and guage mastered. What I really wonder about is how bearing crush and etc. affects the reading and what it finally settles into after being run.

ChucksZ06

iTrader: (9)

I would think the crush would not be more than .0003 to .0004 after running although I have never did a before and after. I know the oil pressure always drops a bit so their must be some opening up of clearances. Using bearing thickness is adding another variable which is never a good idea when measuring. I like to us inside mic and outside mike to double check crank dimension versus acctual id shown on inside mic. This eliminates the error between the 2 mics calibrations.

67SS509

iTrader: (25)

Another thing I rely on is repeatability. I reset the tools and recheck until I get consistant readings to +- .0001"