IB Rod Bearing

James B

Member
Ok, I just finished up fitting and getting the proper clearance on the main bearings. Crank has been freshly turned to .02
on both mains and rods with .02 new bearings. Crank turns smooth by hand. Started in on the rods and pistons. I plastigauge
the rod bearing and have .002 clearance. When I go and turn it by hand, it turns smooth. What got my attention is when I
turn the crank so the piston is either at the most upward position or downward position, the bearing has small amount of
slop as the stroke moves in the opposite direction. There is a small clunk. I can recreate it by finding the point and
moving the crank ever so slightly back and forth. Checked several times with Plastigauge and is still remains .002. I can
move the bearing cap with my hand perpendicular to crank and make that same noise. Its a very small amount of slop. I
decided to take a shim out and it was at .015 but to tight to turn crank. My thought was to "fine tune" the bearing by
filing a small amount at a time to get closer to .017-.019 clearance and maybe reduce the amount of slop I am
seeing/hearing.

Is this a problem? I am worried if I left as is, it would make knocking sound when I get it all put together and running.
I rather look at the details now vs me tearing it all apart again. Any guidance or suggestions will be much appreciated.
You may need a nap after reading this long winded explanation! Thanks again
 
Without being there I would say your fine. With everything dry you will have a small clunk, hence the .002" clearance/gap. The only things I can suggest is make sure you are using/reading the plastigauge correctly. I have known people to use/read the metric plastiguage scale for standard/imperial specs. .002 mm DOES NOT equal .002 inches. You could also mic the journals in multiple places or plastigauge in multiple places to check for an out of round journal.
 
I think you are OK..... couple miss prints in your numbers... you had .002 ( 2 thousands) and you wanted to get tighter so you SHOULD get .0015 ........ or .0017 right ?
 
Oops, yes I did mean .0015 . thanks for pointing that out. Thank you for your response, helps me be confident when I run into these details. I guess I will move forward and start on the others.
 

I'm wondering if the "clunk" you are hearing is actually ENDPLAY and the crankshaft is rearranging itself a bit, fore and aft, at that point.
 
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humm, is the crank oiled or dry when your doing these checks? that sideways movement is the rod end play and you need that, and yes at tdc or bdc that is where the rod is actually without pressure on it. and do not file brgs! you need brg. crush to hold it in place. if the machine shop had the brgs and rods when doing the machining it has to be good. and also the rods shoulds have been resized at the same time. dont want to risk having an egged rod when everything else is new.
 
Update: doubled checked the clearance and lubed and torqued. Turned free with no problems and no small clunk. I must be overly sensitive.(my wife would disagree). Did the remaining three with no problems. I guess it was due to being dry during fitting

Thank you guys for your input. This forum is a valuable resource of knowledge and information. It has been very helpful. Thanks again
 
you are right from being dry. i never install dry brgs anytime. those brgs scratch really easy. i also heard mechanics say not to touch the inside of dry brgs either with your fingers. i dont either, not till they are oiled. same with the pistons and rings make sure they are WELL oiled before installation, not after.
 
i also meant to ask you since you have been rolling it over dry you must have them brgs. all screwed up now. meaning the coating will be all marred , as its so thin.
 

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