Welcome to Club Hot Rod!  The premier site for everything to do with Hot Rod, Customs, Low Riders, Rat Rods, and more. 

  •  » Members from all over the US and the world!
  •  » Help from all over the world for your questions
  •  » Build logs for you and all members
  •  » Blogs
  •  » Image Gallery
  •  » Many thousands of members and hundreds of thousands of posts! 

YES! I want to register an account for free right now!  p.s.: For registered members this ad will NOT show

 

Thread: Main Bearing Failure
          
   
   

Reply To Thread
Results 1 to 5 of 5
  1. #1
    76GMC1500 is offline CHR Member Visit my Photo Gallery
    Join Date
    Aug 2003
    Posts
    1,176

    Main Bearing Failure

     



    No, mine are still holding up fine. My friend just bought a '73 Camero with a 350. It had a little knock to it, but it very quickly began making a horrible slapping noise. He took it to a shop because he isn't much of a car buff, and they diagnosed it as a thrown rod. The car ran rough because it had a cam that didn't match the motor, and it was still running on 8 cylinders. I figured it was a bad rod bearing. So, I suggested they get the GM's stock replacement 350 and transplant that into the car. Back to the point, we pulled the old motor and began disecting it only to find that all of the rod bearings were in good shape except for a few scores where dirt had passed through. There was hardly any discoloration except for a few shiny spots on the upper shells where wear had begun, but that was expected. I was a little worried, because I had just suggested they buy a new engine and this one didn't look like it had anything wrong with it. Well, there was one last part to check, the main bearings. I pulled the cap in the rear of the block and immediatly knew what was wrong. All of the babbit had worn off of the bearing and had been worn well into the copper mid-layer. I proceeded to pull the remaining 4 bearing caps and all were in the same condition. This motor wasn't very high milage as it had not worn a ridge into the top of the cylinder, yet. We did see signs of water in the oil underneath the oil fill cap and breather, but there were no signs of it in the oil pan. Also, the head gaskets appeared to be ok with only a slight browning between the center cylinders. So what I am asking, is what would cause such a failure? Most likely lack of lubrication, but I would also expect the rod bearings to be in pretty bad shape. No bearings spun, either.

    So, anybody looking to buy a 2-bolt 3970010 350 with 882 heads for $300 ish? It's got a cast crank that may be turnable, but I cannot guarantee it. I saw no gaping cracks and there are no spun bearings. It has a .030 bore and due to the low milage a .040 might be enough to clean up the cylinder walls, but I cannot guarantee that without a mic. All of the main caps are there and I kept them in the order and direction they were originally.

  2. #2
    drg84's Avatar
    drg84 is offline CHR Member Visit my Photo Gallery
    Join Date
    Sep 2003
    Location
    Dansville
    Car Year, Make, Model: 1996 Aurora Autobahn edition
    Posts
    1,201

    Sounds to me like the block had water in it, the bearings froze, and started scouring where someone started it up without checking the stick first. engine turns, fires, mains stick to the crank, snap free and take part of the bearings with it. That engine is savable, but not really worth it. However, it would make a really nice table.
    Right engine, Wrong Wheels

  3. #3
    TyphoonZR's Avatar
    TyphoonZR is offline CHR Member Visit my Photo Gallery
    Join Date
    Dec 2003
    Location
    Chwk
    Car Year, Make, Model: 86 S-15 Jimmy sb 400
    Posts
    579

    Detonation took out the mains! Too much timing or too much compression or bad gas.
    Objects in my rear view mirror are a good thing unless,.... they have red and blue lights flashing.

  4. #4
    viking's Avatar
    viking is offline CHR Member Visit my Photo Gallery
    Join Date
    Jun 2003
    Location
    Branson area
    Car Year, Make, Model: 23 T, 53 FLH , 66 C-10 454, 03 CVPI
    Posts
    968

    Kinda pricey for a boat anchor, does it have cool valve covers ?
    Objects in the mirror are losing

  5. #5
    76GMC1500 is offline CHR Member Visit my Photo Gallery
    Join Date
    Aug 2003
    Posts
    1,176

    That's definatly a posibility, Typhoon. That engine had flat top pistons and they were running 87 octane. The advance at idle was 12-15 degrees. I would think detonation would take out the rod bearings first?

Reply To Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
Links monetized by VigLink