Rod Bearing size

Black Bear

Black Bear

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Mar 21, 2005
Location
Raleigh, NC
I messed up a rod bearing on an old Jeep F head last night. The top half fell onto the bottom one and i didnt notice till after I had the bearing cap on it. All of the bearings looked great so I'd just like to order new ones and run it. However I dont know if they are standard or undersized... The back side of the bearing reads

275 020
CB 236 M

Its a Clevite bearing but does the 020 mean .020 undersized?
 
I really dont have any precision measuring devices.. But my harbor freight caliper says its 1.9150" and the spec I have found says 1.9375 to 1.9383"


1.9150 +.020 = 1.9350 dang thats close. The difference might just be the shitty tool I used to measure.
 
Yep, sounds like you've got it figured. 0.020 is a pretty big number. The caliper shouldn't be off by that much- maybe a few thousandths. I've used the HF variety before and they work good enough to verify what you're looking at.
 
you don't want a precise tight fit, a thousandth or 2 is good, oils gotta go somewhere. want a better measure, get some plastigauge ( green )

you did NOT tighten the bearing cap right ?
 
I would reinsrall the cap without the bearing and measure rod end bore in several different directions, just to ensure it didn't get stretched out of shape. You're there now. Do it before it becomes a problem.
An out of round rod journal is just as bad as as scared bearing.
 
Either check now and know or wait until it's running and you know why you have that knock, and know you should have gone that one more step.....

At least you caught it before you ate a crank and rods...
 
I couldnt find a spec for out of round for the rod only the rod journal. But this is what i measured..

2.0390 12 o'clock
2.0385 1 o'clock
2.0390 11 o'clock
2.0389 2:30 o'clock
2.0370 9:30 o'clock


.0020 is the ovalness of the rod.. am i screwed? keep in mind that im using the wrong tool (harbor freight caliper) to measure.
 
Measure another rod without bearing in it, maybe all of them.

Those will be your baseline.
 
Your tool is accurate enough to get s good base line as long as you use it the same in all positions
 
The tool might be accurate enough, but its easy to not hold it perfectly square to the rod.

#2 #1 #3 (the messed up one)
12 2.0370 2.0370 2.0370
1 2.0385 2.0395? 2.0380
11 2.0380 2.0375 2.0390?
2.5 2.0375 2.0385 2.0370
9.5 2.0375 2.0370 2.0380


all of the 11 o'clock measurements were all over the place.. it would read 2.04xx then adjusting the caliper would come down to 2.03xx not sure why that is but all 3 did the same thing.

I dunno but it looks like I didn't dork up the rod.
 
none of the rods will be 100% identical, especially when they aren't torqued

If you're comfortable with the difference in measurements and the cap goes on and off with no difference to the others, you should be ok
Nothing looks terrible from your numbers, clean everything up good install new bearings and pay attention this time.... :flipoff2:
 
No more engine tinkering after midnight for me..

New bearings will be here on Thursday, and hopefully i'll have a running motor by monday. Thanks for the help.
 
same rod you fubar'd the bearing ?
 
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