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Thu Mar 31, 2011 9:00 pm

So I was wondering what the prefered method for checking bearing clearance is. I was taught to measure the main (or rod) bearing bore, then use a ball mike to measure the main/rod bearings and a micrometer to measure the crank (then simply do the math to figure out your tolerances). It never really dawned on me the different brands of bearings would produce different clearances, but it seems that's the case here. My local VW mechanic shop told me that he doesn't even measure the bearings, just checks the rotating assembly by feel... :?

My instructor in college argued that using plastigage wasn't the best method due to the fact you could (technically speaking) build an engine that used a .010" under crank with a .020" under main bearing on one side, and a standard size bearing on the other side and still achieve the clearance you were after. Obviously he was just trying to prove a point (that ticked off employees in bearing production plants could easily throw misc bearings into a box and many engine "builders" would assume the rotating assembly was just a little tight :shock: ).

I have a dial bore gauge now so I was planning on using that, but is the ball micrometer still useful in this situation? Sorry for the dumb question but I had a surgery today and the anesthesia and pain killers have my mind wandering off a bit. :lol: I've never really heard of other methods for doing this procedure and it leads me to believe that everyone uses the same (or a similar) method, or no method at all. Thanks for the input.

Andy

PS-Please excuse spelling errors and rambling, and insert "half baked" emoticon-haha.

Thu Mar 31, 2011 9:15 pm

Measure crank journal with mic.
Transfer that dimension to your dial bore gauge (zero dial gauge to mic)
Then measure bearing (torqued in place) the reading on your dial bore
gauge is your clearance.

Thu Mar 31, 2011 9:18 pm

whatever works for you
My boss thinks a bore gauge is the only way to know for sure
One day we had a contest and the result is we all get the same measurement using our favorite methods, I like snap gauges when boring, bore gauges when honing

You can use a snap gauge, or an inside mic, and adjust it to the ID of what you measure, and then use an outside mic to measure IT.

The advantage either way is you FIND the ID with the snap gauge/inside mic and all this does is transfer the size towhere you can get a mic on it. Then you mic the whichever, and mic the crank. Since you use the same mic you get very accurate measurement of clearance.

When using a bore gauge it is the opposite, you use an outside mic to transfer the size of the crank to the bore gauge, then you rely on the bore gauge to tell you clearance, and the good expensive ones are pretty accurate.

In either case, your accuracy is related to your skill at transfering the size.

Also, you can measure the bearing thickness, there is a kind of mic that has a ball shape on one anvil, OR you can buy a little thingy that snaps a ball bearing TO one anvil of your 0-1 mic
The boyscout method is to tape, yes tape, a ball bearing to one anvil of your mic!

NOW you can see how much excentric is built into the bearing, and see if they are all the same thickness. Good quality stuff you never find a problem. Cheep stuff? i seen .001 variation in thickness, and that is F'n stoopid bad quality. jeez!

Thu Mar 31, 2011 10:12 pm

Thank you both for the input. I hadn't thought about transferring the micrometer reading to the dial bore gauge, but it makes total sense! Thanks for that trick SRP1. The funny part is I used the micrometer to check my dial bore gauge for accuracy when I first bought it...You would think I would have caught on sooner to that trick when actually measuring things! :roll: You are supposed to check a new tool with unknown accuracy by using another measuring device with unknown accuracy, right? :lol: I "think" that's standard procedure(?).

Modok, I have one of the "ball" micrometers you mention already (for measuring the bearings). That was the only method I used before I became aware of the differences in tolerance between bearing companys...you're abosolutely right, it is pretty lame that quality control is what it is nowadays! How many guys in the industry actually check the measurements of all those parts anyways? I know of 2 or 3 (off the top of my head) that build engines and claim to be "professionals", yet they have no idea how to measure (or worse yet, WHY to measure) parts before assembly! GEEZ!

I used to use snap gauges for measuring bores, but I could never quite get my measurements to transfer exact everytime...I guess I don't have the magic hands for acheiving consistant results! Plus the dial bore gauge is quicker and more fool-(that's me)proof. Thanks again for enlightening me on the subject.

Andy

Thu Mar 31, 2011 10:21 pm

yeah, to each thier own
i find the single slider sterret snaps to be very good, but they are worthless if the slide action is not smooth(if monkeys overtighten them). China quality snap gauges are absolutely worthless in comparison.

You pretty much have to measure the ID of the bearing in the case with it torqued, since the main bearings are quite stout; they do not "crush" very much compared to normal engines. Even in normal engines, sometimes I find that reducing the housing bore .001 only tightens the bearing up .0005"-.0007", a bearing does crush but seems the housing stretches somewhat too.

Thu Mar 31, 2011 10:55 pm

modok my friend..

this is what i do...

mic the journals

zero out the dial bore guage based on the mic's measurement

bearings on the saddle torque the case (or in honda's the main caps lol)
and check the diff with the dial bore guage that was zero'd on the journals

is this decent?

Thu Mar 31, 2011 10:57 pm

its also how i thought i can check

"crush" by checking the bearing's OD

vs the saddle's ID ?

lemme know if ive been lost all this while LOL

Thu Mar 31, 2011 10:57 pm

youngnstudly wrote: Thank you both for the input. I hadn't thought about transferring the micrometer reading to the dial bore gauge, but it makes total sense! Thanks for that trick SRP1.

Your welcome, good luck with your build and recovery.

Thu Mar 31, 2011 11:00 pm

Thumbs up Ralf!
that's perfect

Only reason I use the snap is it's faster and doesen't mark up the bearings as much. i don't care about a few marks personaly but some"professional" engine guys complain about anything they can see :roll:

yeah the crush should be at least .002 in the case. The center split bearing seems to have more like .003 or even .005 crush, not sure why but that is how they are sometimes.

Thu Mar 31, 2011 11:02 pm

no the only reason u use that is cuz u have it

hahahaa

i fail i am limited in tools compare to u my friend!

im glad though i wasnt lost? this is a good refresher/topic

until sum1 starts coming in arms swinging nuts sagging saying.. no wrong
do it my way LOL

Thu Mar 31, 2011 11:05 pm

NSR must be missing this
i'm sure he would know the "best" way,
HEY NSR WERE ARE YOU?

Fri Apr 01, 2011 10:15 pm

SRP1 wrote:
Your welcome, good luck with your build and recovery.

Thank you for the well wishes...My shoulder is doing fine as of now. As long as it doesn't get infected (or some idiot walks up and punches it being a smartass) I should be fine. Hopefully the engine build will go smoothly too! I am almost ready to have my parts balanced.

Andy