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Found out what blew in my engine. What happened?

Discussion in 'The Hokey Ass Message Board' started by Stevie Nash, Sep 30, 2012.

  1. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    I blew the SBC in the Nash back in May. Finally got over the depression of the whole thing and pulled the engine yesterday.

    The engine had some noise prior to the "incident", I had hoped it was a lifter. My fear was that it was a connecting rod bearing. So when the engine blew I assumed that's what it was.

    Dropped the pan and found the remains of the #6 piston blown to bits. Found some play in #3 and #4 connecting rod bearings.

    So I'm assuming that I was right about the noise, but that ultimately was not the failure point. What the hell happened? And can I expect head damage with a blown piston?
     
  2. squirrel
    Joined: Sep 23, 2004
    Posts: 47,935

    squirrel
    Member

    Without pics, we're blind....
     
  3. Hard to tell without pics.

    But if you lost a piston and they were Hypereutectics, my money is on too tight of ring gap.
     
  4. GOATROPER02
    Joined: Mar 22, 2006
    Posts: 2,059

    GOATROPER02
    Member
    from OHIO

    If you lost a rod bearing the piston was prob bouncing off the cylinder head..... Cast or hyper won't stand any of this..... Piston just failed before rod had a chance to......



    Your engine was trying to tell you something..... But nobody listened
     

  5. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    Pics attached. Could it have been from running too rich or too lean?
     

    Attached Files:

  6. henryj1951
    Joined: Sep 23, 2012
    Posts: 2,304

    henryj1951
    Member
    from USA

    da mater much at this point WHAT blew...
    one can de- tork as you go and take a TON of pictures..
    and it still will take some (luckie) work to find / see what started the
    process.
     
  7. TooManyFords
    Joined: May 21, 2008
    Posts: 553

    TooManyFords
    Member
    from Peotone IL

  8. Deuces
    Joined: Nov 3, 2009
    Posts: 19,692

    Deuces
    Member
    from Michigan

    Only 1500 sheckles for a brand new goodwench 350 long block....
     
  9. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    Yah,it's tempting. But I bought a running nailhead. Problem is that it will cost more (headers, different tranny, etc.) to get the used nailhead on the road than a brand new sbc. But I've never been a Chevy guy. In lies my struggle....
     
  10. Engine man
    Joined: Jan 30, 2011
    Posts: 3,476

    Engine man
    Member
    from Wisconsin

    Looks like the piston broke at the pin boss. Is the pin blue on the end? It looks dark in the picture. It could be that the pin was too tight causing the piston skirts to slap the cylinder walls, hence the knock and inevitable piston failure.

    You can count on at least bent valves in the head.
     
  11. Jalopy Joker
    Joined: Sep 3, 2006
    Posts: 26,115

    Jalopy Joker
    Member

    maybe the "Nailhead Spirits" did it.
     
  12. squirrel
    Joined: Sep 23, 2004
    Posts: 47,935

    squirrel
    Member

    The dark end of the rod is from heating it to install the pin. That's normal.

    Like was suggested, it could be too tight of ring gap with hypereutectic pistons. This can be more of a problem if it runs lean and heats up the piston, the ring will expand so much that it butts, and locks the piston in place hard enough that the downward force on the pin pulls the piston apart.

    If you take it apart the rest of the way, and measure the gaps of a couple of the top rings, you can see if that's likely. More pics....we like pics...
     
  13. Vandy
    Joined: Nov 15, 2009
    Posts: 368

    Vandy
    Member
    from L.A. Ca

    You say buy American, because you give a crap ??

    You do know that all new Chevy motors are made in MEXICO !
     
  14. Mr48chev
    Joined: Dec 28, 2007
    Posts: 28,522

    Mr48chev
    ALLIANCE MEMBER

    I'd say it wasn't a "Chevy" problem but a not paying attention to details problem.

    it does appear that the piston pulled apart at the pin or at the bottom ring land and beat the bottom part of the piston until it broke.

    That "noise" could have been a cracked piston or one missing a skirt rocking in the bore or the bottom of the piston pounding on the top half until the bottom half fell in the pan.

    If it has been rebuilt lately who ever assembled it may have put slightly larger rings in it (like .010 over in a standard bore) which is fairly common with builders who size and fit each and every ring but a big mistake with guys who don't.
     
  15. one37tudor
    Joined: Mar 3, 2001
    Posts: 146

    one37tudor
    Member

    Most of the new LS engines are made in Canada.
     
  16. Commish
    Joined: Jan 9, 2010
    Posts: 379

    Commish
    Member
    from NW Ok

    I don't think you are going to get a definitive answer from one blurry picture, the dark end of the rod looks more like a shadow to me than anything. If you drove it with an ongoing knock that you thought might be a lifter, my guess is first problem was a cracked piston, but like any other opinion you are going to get from this post, it is only a guess.
     
  17. Deuces
    Joined: Nov 3, 2009
    Posts: 19,692

    Deuces
    Member
    from Michigan

    That I didn't know.....OOPS!..:eek:
     
  18. squirrel
    Joined: Sep 23, 2004
    Posts: 47,935

    squirrel
    Member

    huh, they say right on them HECHO EN MEXICO. They have for decades.
     
  19. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    Yes, it may be time to just move on. I did not build the engine, but I just wanted to make sure that something I did (tuning, etc.) didn't cause this. I thought maybe the problem would be obvious to some of the experienced engine guys...

    Stevie
     
  20. squirrel
    Joined: Sep 23, 2004
    Posts: 47,935

    squirrel
    Member

    If you can post a few clear pictures of the bottom side of the head, and the top of the block assembly, it might help the figuring out process. You didn't give us much to go on.
     
  21. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    I will post some more pics when I remove the head.
     
  22. Stevie, dont waste time wit the pictures, thats sorta like pics of the deceased in the casket....its already too late for a good picture......
    Just get another sound 010 block have it bored slightly as you can and get a rebuild kit from Northern Auto in Sioux City[Mexican pistons] yeah ,but I never had any trouble from any of them and thrashed em pretty hard too.
     
  23. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    Here are some pics....

    What's left of the bottom half of the piston.

    [​IMG]

    One of these is not like the other...

    [​IMG]

    Uh oh.

    [​IMG]

    Double whammy!

    [​IMG]
     
  24. captain scarlet
    Joined: Jun 11, 2008
    Posts: 2,415

    captain scarlet
    Member
    from Detroit

    Did the valve fail? I ask since a friend of mine lost his engine when the valve stem failed.
     
  25. Johnny Wishbone
    Joined: Aug 10, 2009
    Posts: 314

    Johnny Wishbone
    Member

    Dropped an exhaust seat, bent the valve and shoved the valve up the piston's ass. I think...
     
  26. Mr48chev
    Joined: Dec 28, 2007
    Posts: 28,522

    Mr48chev
    ALLIANCE MEMBER

    It does appear that the head snapped off the valve. I can't see any marks that indicate that other pieces like a bolt or nut were in there. When a bolt falls down the intake and gets in a cylinder you usually see the imprint of the threads in either the piston or head. I'd second buying an engine kit from Northern Auto parts and getting a new to you 010 block and going again.

    You haven't been in the habit of wringing it out and floating the valves have you?
     
  27. Jeff Walker
    Joined: Feb 6, 2007
    Posts: 498

    Jeff Walker
    Member

    My money is on that the head of the valve snapped off. I have had that happen to two engine in my lifetime. That's why pretty well all engines I build anymore get at least a new set of exhaust valves.

    BTW How often did you make a habit of buzzing it real hard??:D
     
  28. theHIGHLANDER
    Joined: Jun 3, 2005
    Posts: 8,178

    theHIGHLANDER
    Member

    The last time I did that to a motor (hell, the only time!) I was giving it an overdose of N2O. I didn't know it at the time, but I had a plate that was modified by Kurt Urban back in the day. What I thought was a 100-200 shot was more like 150-400. Oops. I was called by the guy I got the plate from. "Hey Jocko, I think I gave you my plate instead of the one you were supposed to get. Can you count the holes in the bars for me?" "Uh, yeah I could but it won't matter much now." "Uh oh, you didn't run it did ya?" "Yeah, but not for very long." They called me Kavorkian for the rest of that season. It happens once in a while. Reload and keep shootin is all you can do.
     
  29. Kevorkian, thats funny...
     
  30. Stevie Nash
    Joined: Oct 24, 2007
    Posts: 2,999

    Stevie Nash
    Member

    So the head breaking off the valve would cause the head of the piston to lodge at the top of the cylinder and pull apart?
     

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