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Discussion Starter · #1 ·
Hey everyone. This is my first time installing a crankshaft, and I am looking for a bit of advice.

First of all, I don't quite understand something I read in the factory service manual. (This is for an 87 YJ.) It says that the lower connecting rod bearing inserts should be installed DRY. Am I mis-understanding, or is there a rational explanation for this? Here's a couple quotes from the book:

"Wipe the journal clean of oil. Lubricate the upper bearing insert and install in the connecting rod."
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"Install the lower bearing insert in the bearing cap. The lower insert must be dry."

Say what? Are they talking about lubrication of the back-side of the bearings, or of the actual bearing surfaces? I can't understand why you would want to mate a dry bearing up to a dry crank journal.

My other question is regarding cleaning the crank. It's a re-grind that I picked up, an I obviously want to make sure it's clean before I put it in. What's the best way to do this? Should I hose it off with soap and water and then re-lube the journals, or should I just wipe them down, or what? I'm concerned about rust, but I'm also worried that if I don't hose it off I might end up with crap stuck in the oil holes or on the counterweights that I didn't notice, which of course will then end up in my motor.

Thanks. :) Any help appreciated!


 

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/wwwthreads_images/icons/tongue.gif There is no reason to lube in back of the bearing shells, EXCEPT to provide a seal for the oil pressure on the block side of the mains only. We always kept it metal to metal (no lube) on the rod and main caps to effect good heat transfer. The main thing is that they are perfectly clean, and a good fit. You can use a hi-pressure solvent gun to blow the oil passages in the crank. Then use the same thing to clean the outside. Don't forget to check the rods and mains with plastigage. Then use lube on every journal for final assembly...making sure you globber some on the all-important thrust face./wwwthreads_images/icons/smile.gif

CJDave
 
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Discussion Starter · #3 ·
Hey thanks for the reply! Just want to make sure I got this right... so I should lube both sides of the upper rods and mains, and just the bearing surfaces of the lowers?

Also, I have some "assembly lube" which appears to be a very lightweight oil... smells a lot like gun oil. Is this preferable to using motor oil, or something like Motor Honey?

I don't have a gun for blasting the oil passages out, but I do have a few cans of brake cleaner, and they spray with some pretty high pressure. Guess that ought to do the trick for the cleaning.

Thanks again. :)


 

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/wwwthreads_images/icons/tongue.gif very light oil only on the surfaces next to the cast iron. There is a regular grease used for cranks and rod bearings that installers use. Looks like white moly. /wwwthreads_images/icons/crazy.gif

CJDave
 

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In lew of a high pressure solvent gun another method is to get journal brushes. These look like mini bottle brushes - ones from the auto paint stores for cleaning spray guns might do.
Usually your machinist will put your ground crank into a large parts washer after grinding and rinse it off with water and then compressor air dry it eliminating rust.
To make sure your crank is super clean, I suggest you scrub the oil journals - all of them - out with solvent and the brushes. Rinse, then use soap and water to again scrub the journals and the exterior. Then if you quickly compressed air dry it (especially inside the journals and bearing surfaces) you will have a squeeky clean crank.
I suspect Dave is right about wanting to create a hydraulic seal underneath your upper (block) bearing surfaces (these have the oil gallery journals), yet it is not such a good thing to have the cap bearing floating off the cap due to oil here, creating possible bearing distortion and too tight of clearance on startup.

JAF
 
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Discussion Starter · #6 ·
i prefer lubriplate #104(or is it 105??:p they only make one so you cant get it wrong. it comes in a white and blue tube). i usually clean the crank in solvent, then in soap (tide works good). dry off and give the crank a light coat of oil to prevent oxidation. always lube the bearing to crank surface, but i leave the bearing back side dry. oil will eventually work its way back there, so no need to add any. always gage all of your clearances, and be very sure to torque the crank in exact order in three or four increments.

dan

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