Bent Pushrod?

Discussion in 'Big Block Cadillacs' started by Hoss50, Mar 30, 2020.

  1. Hoss50

    Hoss50 Member

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    Can someone help me get an idea of what may be the reason behind a bent pushrod in a 76 caddy 500 motor.

    It is basically a stock motor with unknown miles. The oil pressure is fine. The motor sat for a long time, but ran well when I resurrected it. The only modification is a new timing chain set 4* advance if I remember correctly.

    I resealed the motor fully expect head gaskets when resurrected it for my project. The motor seemed in good shape from what I could see.
     
  2. 5one9

    5one9 Active Member

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    How long after you started it for the first time did it take to bend the pushrod?
     
  3. Hoss50

    Hoss50 Member

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    It ran fine for several years. It didnt get run that much, and had a couple time when it would sit for months in my garage, but it normally ran monthly or more.

    This motor is in my offroad truck.

    When it bent a buddy had it. They said the more ran a little rough and stopped running. Are a little bit it fired up, but muse have been when it bent because they said it ran rough after that headed back to the trailer. I trust them enough to know they weren't doing anything stupid lIke revving it enough to float valves, etc.
     
  4. Cadillac Kid 1

    Cadillac Kid 1 Well-Known Member

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    What do the rocker arms and "T" stands look like, and how about the valve spring on that valve?
    Greg Surfas
     
  5. Hoss50

    Hoss50 Member

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    Here are some pictures. This is the passengers side cylinder bank, 3rd from the front. #4 on the intake markings.
     

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  6. Hoss50

    Hoss50 Member

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    Here is the bent pushrod if it helps.
     

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  7. 48Austin

    48Austin Safty First! Then pull the trigger!

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    Looks to me that this engine had some serious neglect issues. Don't worry about what caused this. Time for a tear down and rehash.
     
  8. Cadillac Kid 1

    Cadillac Kid 1 Well-Known Member

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    Looking at the pictures I would suggest getting a new pushrod, doing a compression test and if that turns out okay I would run the engine. A sticking valve might have done this and if the valve/guide clearance has somehow diminished it will bend another rod. With a stock motor being "non interferrence" it is worth a try befor you go looking further, other than making sure the lifter has not frozen up.
    Greg Surfas
     
  9. Hoss50

    Hoss50 Member

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    I just ordered another rod. I am going to try and seafoam it and flush it. If it runs it runs.

    If not I have a 472 sitting here at I might try and run next. It is unknown condition though too so it would be another junkyard hail mary. It is supposed to be a 10.5:1 motor to which would be cool if it was a runner.

    The insides of the motor look cleaner then this one, but it will require some TLC to even get it in my crawler to test.
     
  10. richie49

    richie49 Active Member

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    I had a pushrod bend like that on my engine. My project sat for long periods of time before I started driving it.What I think happened on mine was the lifter were kinda weak
    and if the engine fired up fairly quick everything was ok because the oil pressure pumped up the lifter . But on some days the engine would take a while to fire up and the lifter would collapse
    and rattle a while till it pumped up. ( it was the #7 cylinder)One day it was rather cold natured and when I started it it tried to die so I reved it some and it bent the pushrod.It must have poped out due to the slack in the lifter ,and jammed itself on the rocker and when it pumped up bam bent pushrod. I didn't rev it to the moon just tapped it to get it to smooth out at idle.
    I put anouther pushrod in and it never happened again .I know when my bent.Yours bending is harder to check on since you wern't there. Good luck with it.
    Richard richie49
     
  11. PJ McCoy

    PJ McCoy Well-Known Member

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    Agree, when the motor sits for a season, its best to disconnect the dizzy and turn the motor over to lube everything "Before Start up"
    Also if the motor got into valve float offloading/ truck pull etc... That may be the cause. Just go through it methodically.
    Keep us up to date.
    PJ
     
  12. 48Austin

    48Austin Safty First! Then pull the trigger!

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    Why is everybody so scared to rebuild an engine? It doesn't take much. Afraid of finding a "Real problem"?
     
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