Replacing my main and rod bearings.

Posted by packinkimber45, Jun 25, 2008
Cylinder Head & Short Block - 4G63 cams, valvetrain, pistons, rods, stroker kits, 6-bolt swaps, hybrids, etc. Read this Forum's Strict Guidelines.

  1. packinkimber45

    packinkimber45 Proven Member

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    Hey everyone. I decided since my motor is already out and my oil pan is off anyways that I should replace my main and rod bearings as precaution and insurance. I am replacing it with oem bearings. I have a few questions. First off what should I have the machine shop do as far any work to the crank and inspections. Never done this before and I want to do it right. Magnafluxed/micro polished/and check measurements? When I plastigaged the main bearings most of them were .0015 in. and one was like .002 inch. Does this mean I just need to order standard size bearings? When I did the plastigage I just simply took out the lower bearings/cleaned off oil on bearing faces and journals. I did not take the crank out to clean the other side of the crank journals and the upper bearings, should I have done this? How about where the bearings mate to the block, do I need to clean off any oil in between there too? Run a tap in all the threads so it doesnt affect my torqueing? Also I know the torque sequence, but when taking the bolts back out do I go reverse of the torque sequence for the main caps or same sequence of install? Like I said I have never done this type of procedure before, when I check my rod bearings is there anything I need to know before I loosen the nuts on them? Such as pistons will automatically drop towards the head, crank needs to be tdc/bdc/turned so rods are on sides of crank? Do I need to support the rods while I am taking them off so they dont just fall down the cylinder towards the head? I have done a lot of reading and searching, not much info I found. When installing the bearings permanently should I use engine oil or assembly lube, manual states engine oil but I read people using assembly lube, what are the pros and cons to both? Also do I lube the back side of the bearings that mates to the block and main caps, or just the parts that contacts the journals? This is all overwhelming sorry for the long post. Thanks.
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  2. RoasT BeeF

    RoasT BeeF Proven Member

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    It is a good idea to have the crank micro polished if possible instead of having it turned. Its up to the machine shop basically to decide if it is in good enough shape to be polished. You will also want the rods to be reconditioned. If you go this route (polish crank/recondition rods) you can go back in with standard size bearings.

    After you remove the old bearings you will want to clean the bearing surfaces thoroughly both on the block and the cap side. It might be a good idea to take the block to the machine shop to have it hot tanked to make sure it is totally void of all oil and contaminants. You may also want to get it line-honed. If you absolutley must, you can get away with just cleaning the bearing mating surfaces with some brake cleaner. You want to make sure these surfaces are absolutely clean. You do not want to lube the back side of the bearings. The bearings need to "stick" in place. This will not happen if there is oil/assembly lube between the bearing and the block/cap, rod/cap and you will spin a bearing.

    When you are removing the bearing caps you will need to untorque in reverse order of install.

    When removing the rod bearing caps the rod isnt going anywhere, you will have to physically push it out of the bore to remove it.

    I recommend using assembly lube vs. engine oil when assembling parts. Its thicker and has a little more "stick" to it so as not just to run all over the place when torquing things down and will provide better lubrication on initial start up.

    I believe I have addressed all your questions. :thumb:
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  3. packinkimber45

    packinkimber45 Proven Member

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    Thanks man, it took awhile to get answers on this thread. Unfortunately I took the crank out and it had a bad nick in the main journal. Looks like it was dropped on one of the bearing corners when it was being installed before. It is bad enough that it cannot be just polished. I am in the process of getting a used crank from a vendor that only has 46k mi. for $75 plus shipping. I wont say who...:sneaky: atleast until I get it. After I get that I am ordering a set of acl race series mains and rod bearings. I am not doing any recondition of the rods since I dont want to go thru all that. This started as doing tbelt/water pump/and oil pump. Funny how a simple job turns to almost a rebuild. Thanks again.
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  4. 1g4my2g

    1g4my2g Proven Member

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    Great Info Guys! After spinning a rod bearing on my built motor at just under 2miles I need to go back and check EVERYTHING on the next build.

    Thanks
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