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Main bearing pics and opinions

Discussion in 'The Garage' started by Thumper, May 28, 2005.

  1. Thumper

    Thumper 1/2 ton status

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    I drained the oil today... lots of goo... mud that is in the oil. It wasnt white and foamy, but settled in the bottom. So I pulled the pan. It appears the oil pickup was submerged not only in oil, but gooey mud as well. No wonder my pressure wasnt great. I spun the oil pump in varsol till it ran clean, then washed the pan out. Then I popped #4 main cap off. Heres pics of what I saw. My question is: I know these arent great, but will these last in a motor that sees no long highway trips (not more than 30kms one way to the trail), occasional runs into town (15kms round trip) and lots of wheeling?
    I figure if I put in some cheap oil and a filter, run it around the block, drain it, do it again, then drain it and put in some good stuff and a new filter, (as long as the pressure comes up) it should be ok right? IF there isnt any noise, IF the pressure stays good, IF ... maybe?
    Take a look.
    Thanks
    Mike

    main#4-1.JPG

    main#4-2.JPG

    main#4-3.JPG
     
  2. Seventy4Blazer

    Seventy4Blazer 3/4 ton status

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    how does the crank look? an inexpensive set of main bearings wouldnt cost to much. a pain to put in but maybe worth it.

    would i run it given your plans or driving style, yeah... i would. i drove my 74 around with a busted piston skirt for 20k miles. the block ran fine when i pulled it and planed on running it without rebuild till it blew... then i came across a smoking deal on a running 350 to use instead so i can use my high nickle block for a HIGH HP motor... anyway, I personaly would look into changing the mains. its apain, but can be done in the truck. if you think its to much hassle like i do then i would run it as is till boom, but be looking for a new motor as time goes on.
    Grant
     
  3. sweetk30

    sweetk30 professional hooker Premium Member

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    that set is tost!:shocked: :eek: :whistle:
     
  4. 3 on the tree

    3 on the tree 1/2 ton status

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    How far from home do you want to be when it quits? Run a fingernail across the crank journals. If they still feel smooth, then throw a new set of bearings in it and go. If the journals feel rough, then anything you do is just a band aid till it blows.
     
  5. mouse

    mouse 1/2 ton status

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    I would definitely change those bearings! If the crank is smooth, run it, otherwise send it in to be polished and run a size up on the bearings. You should be able to drop the crank fairly easily...but might take a few days to get back from a machine shop.

    At least change those bearings!
     
  6. 4X4HIGH

    4X4HIGH 1 ton status Premium Member GMOTM Winner

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    If you decide to install new main bearings there is something you first need to know and watch out for. When GM assembled engines they commonly used what is called selective fit bearings. These are bearings that are anywhere from .0001"-.0009" undersize. That is tenths undersize and not thousandths it will have the size shown on the back side of the bearing. It will look something like GM .0005" which is the most common size i've seen used. What does this mean to you, it means that you will have more clearnce if you just use a standard size bearing in its place. Now for the bad part of all this, those bearings ARE NOT available to the public anywhere. If your engine has selective fit bearings you would have to pull the crank and have it reground and then install the proper size bearings for the size of the reground crank.
     
  7. rcamacho

    rcamacho 1/2 ton status

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    Bearing is shot. How's the crank? Proably prudent to pull the engine and go through it unless you're willing to risk rod/crank failure.
     
  8. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Mike, those bearings are FUBAR...the only thing i'd run those in would be a demo derby car.

    Rene
     
  9. mountain4x4

    mountain4x4 Registered Member

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    Sounds like plastigauge is in order. I'd still replace 'em, clearances can vary .0005 and still be within spec. Since the crank will be dropped anyway, if the plastigauge reads too tight or loose of a clearance, a machine shop can take care of it for you without spending too much $$$.
     
  10. 89GMCSuburban

    89GMCSuburban 1/2 ton status

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    Check out your distributor gear, too. Those wear fast with bad lube. That looks like abrasive wear more than lack of lube, sand or dirt got in there to make it look like that.
     

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