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Unread 03-10-2012, 10:07 PM   #1
Blue83CJ7
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258 Bearing Swap - Not good so far...Help?

I had low oil pressure, so I decided I would put new bearing shells in...

Problem 1: It looks like the rod bearings I ordered don't have the semi-cicle oil hole in each half and they didn't let the cap sit flush when torqued, so I know those are wrong and I didnt' install them.

Problem 2: After I got all my crank bearings in, lubed up with assembly lube and torqued them down I couldn't get my crank to budge, even while torquing the flywheel bolts to 100 ft/lbs and trying the starter. I loosened them up real loose and the started would turn it, but still very slowly.



On the crank bearing, I assumed 10 was .010 undersize, and the 200 on the rod bearings was .020 undersize.


Did I get the wrong size parts?
The two on the left are the old/new rod bearings and the two on the rights are the old/new main bearings.



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Unread 03-10-2012, 11:15 PM   #2
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After reading a few threads about the factory using different sized bearings, and having to measure to the .0001, I am really bummed I convinced myself I should "just" replace the bearings...

Looking back on it, it sounds a lot easier than it really is and I think this little experiment just put me in the market for a reman engine many hours and dollars behind...

Pretty crappy weekend, but hopefully I can at least get it back together and rotating as a core and I am only out $100 for the bearings
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Unread 03-11-2012, 08:16 AM   #3
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You sir are having a bad week, sorry!
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Unread 03-11-2012, 08:32 AM   #4
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Alright you can salvage the week end and learn a lot in the process, making this adventure a success. First thing you want to do is mic the old bearings, this would give you an idea if they are undersized or not. Then get the appropriate size mains (maybe even just one) and some plasti-gauge, fit and test each main bearing. Then do the same with the rods. If you have a clearance issue, get the right bearings, it's been years since I used them but they use to make bearings in off sizes by the thousandths on the low end and by 5 thousandths on the upper sizes.

Regardless of the age or condition I plasti-gauge every bearing I install and if it does get the right clearance I do what is necessary to make it right. This includes freshly machined parts and bearings. I also will turn the engien a few rounds between the installation of each bearing.

Hope this help, and good luck.
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Unread 03-11-2012, 08:54 AM   #5
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3 things: there is a way to take a micrometer and measure your old bearings, measure what you bought and "do the math" by knowing the rod and main journal bore diameters,the rod and main journal standard diameters,and the the thickness of the bearing shells.
If you don't understand what I'm talking about, respectfully this procedure may be past you already. You can "mic' the rod journals w/ the crank still in the block, but not the mains.
At this point it may be easier to pull the crank and take it to a shop and have it mic'd and polished, order the right bearings and put it back.
Finally, since they were AMC bearings to start with, the PROBABLY were standard size. Probably....
If anyone has a FSM and can find the bore diameter's of the rods and the bore diameter of the main bearing assy's, you could do the math. If you determine that and come up w/ a mic to measure the AMC bearing shells, I'll try to figure it out for you.
Sux to be you right now.
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Unread 03-11-2012, 09:18 AM   #6
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At the time these Cj's were built no manufacturer would use an undersized crank in production. All of them had what they called high limit bearings. Those were std., .001, .002, .003. They were color coded plain being std. AMC also stamped the block on an external pad if high limit bearings were used. Judging by the bearing shells in the photo you have AMC std. bearings. those markings in the photo that you might have thought were size marks are just production run numbers the shell would have been clearly stamped if over standard.
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Unread 03-11-2012, 09:37 AM   #7
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I cant speak for 83 exactly, but manufactures have used undersize cranks and even oversize bores in production engine for many years from the 60 well into the 90s that I personally know of. I have taken apart or been around KNOWN factory engine with these parts. And these are from the guys (big 3) with money so I am reasonably sure a car company working on a shoe string budget would used just about anything. I agree the OP are standard though, but oversizes are not unheard of.
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Unread 03-11-2012, 09:48 AM   #8
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Maybe this will help?

From the 1984 - 1986 FSM Engine Spec for the 4.2L (258 CID) Page(s) 1261, and 134 of the downloaded PDF here.
crank.jpg   oversized.jpg  
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Unread 03-11-2012, 11:22 AM   #9
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I actually have an '80 CJ7 now ( i can't change me screen name from my old jeep, but I will update my profile/signature) so I don't know if those pages from the FSM still apply...

And yes, I know I am in over my head in terms of tools, place to work, time, money and most importantly knowledge about the specifics of engine building... i think if I just had the right size bearings, it would have gone alot better, but I understand I am taking shortcuts and it should be done "the right way".

Having said that, here are the measurements I was able to get with a mic on the bearings and calipers on the crank rod & main bearing surfaces

I don't have a boss between my coil & distributor with a stamp, or any colors on the bearings, but I do have a 005C20 stamped on a flat rectangle boss in front of the distributor?

----------------------------------------
Old Crank Bearing Thickness - .096
New Crank Bearing Thickness - .101

Old Rod Bearing Thickness - .054
New Rod Bearing Thickness - .064

Crank Main Diameter 2.4985
Crank Rod Diameter 2.0955

If I take my Crank main Diameter plus my old bearing thickness plus .002, I get: 2.5965 which is an estimate of my main journal bore before I swapped the bearings in, right?


If I take the difference between my previous journal bore and the mid-range factory journal bore, I get

2.5965 - 2.4998 = .0967


That doesn't make sense, does it? Shouldn't it be more in the range of .010-.030?
bearings.png  
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Unread 03-11-2012, 11:48 AM   #10
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Quote:
Originally Posted by Blue83CJ7 View Post

On the crank bearing, I assumed 10 was .010 undersize, and the 200 on the rod bearings was .020 undersize.


Did I get the wrong size parts?
The two on the left are the old/new rod bearings and the two on the rights are the old/new main bearings.

So did you actually order undersize bearings based on that assumption?
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The advertised position for a topless, dirty jeep girl has been filled......by my wife. Thanks to all that applied.
<------------and yes, that is her.
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Unread 03-11-2012, 11:48 AM   #11
Blue83CJ7
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Also, all math aside:

If you guys re right and I have standard bearings, that would mean that I bought bearings for a undersized crank and rod surfaces (what's the name for the crank part, not the journal?), meaning the bearings are thicker, and that would cause the problem I am seeing?

I hate to be out $100 for another set of bearings, but that's better than needing a professional rebuild or reman engine. If I can get the right size I should be ok since I am now a pro at popping these things in and out, I just might need another tube of assembly lube.
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Unread 03-11-2012, 11:50 AM   #12
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Quote:
Originally Posted by Blue83CJ7 View Post
Also, all math aside:

If you guys re right and I have standard bearings, that would mean that I bought bearings for a undersized crank and rod surfaces (what's the name for the crank part, not the journal?), meaning the bearings are thicker, and that would cause the problem I am seeing?

I hate to be out $100 for another set of bearings, but that's better than needing a professional rebuild or reman engine. If I can get the right size I should be ok since I am now a pro at popping these things in and out, I just might need another tube of assembly lube.
That's what I was getting at in my post above. Undersize bearings used where a standard set should be could cause what you are seeing.
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The advertised position for a topless, dirty jeep girl has been filled......by my wife. Thanks to all that applied.
<------------and yes, that is her.
:-D
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Unread 03-11-2012, 11:50 AM   #13
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Quote:
Originally Posted by jeepwhore View Post
So did you actually order undersize bearings based on that assumption?
Yes... "I read on the internet" that it was supposed to be stamped on the shell


And yes, I feel stupid about it now...
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Unread 03-11-2012, 11:52 AM   #14
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Quote:
Old Crank Bearing Thickness - .096
New Crank Bearing Thickness - .101

Old Rod Bearing Thickness - .054
New Rod Bearing Thickness - .064
BINGO!!!! you have a STANDARD crank.
You said you bought (as evidenced by markings on bearing shells) .010 OVERSIZED mains and .020 rods.
main new .101
main original.96
difference .005
x2 (both bearings) .010

New rod brg. .064
old rod brg .054
difference .010
x both sides .020

with the new sizes a given: 020 and 010 oversize, subtracting those figures from the thickness comes out to .000 oversize. Standard.
Good luck on getting the FLAPS to take 'em back after out of boxes, lubed, and installed (don't even ask) but just order the standard ones and put it together.
As 346 sez, plastigauge 1 rod and 1 main just for your own satisfaction (should do that anyway) and put 'er together.
What confuses you/most is that you confuse over/undersize. The stock crank and brgs are a standard size, machining and wear make the crank smaller and OVERsize bearings (thicker) are used to compensate for the removed material on the crank.
If you use OVERsize (thicker) bearings on a standard crank it will bind it up.

No longer sux to be you.
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Unread 03-11-2012, 11:55 AM   #15
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Quote:
Originally Posted by mopar408 View Post
......No longer sux to be you.
Well not for that reason anyway!.....

At least your only out $100 instead of $1000 or more.
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The advertised position for a topless, dirty jeep girl has been filled......by my wife. Thanks to all that applied.
<------------and yes, that is her.
:-D
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