Broken Rocker Arm

Discussion in 'Engine Topic' started by connorbe, Sep 3, 2017.

  1. connorbe

    connorbe Member

    Jul 5, 2017
    South Dakota
    Hey Guys,

    I think I've read just about every single online resource about broken rocker arms in SBC 350's today, but I haven't come across someone in quite my same situation. I figured I ought to tap the Nasty Z28 knowledge base on this one for some input:

    I was driving today and suddenly started hearing a loud mechanical pinging sound from under the hood, and it started driving a bit rough. I pulled over, removed the air filter and started it again. The engine was backfiring through the carb and still making that metal pinging sound, so I got a flatbed home.

    When I got home I took the valve covers off and discovered the the rear drivers side exhaust valve rocker arm had cracked at the pushrod seat causing the roller end to slip off of the spring, and the pushrod was loose. I was able to turn the rocker arm and pull out the pushrod without actually loosening the rocker arm at all.

    The unique part about this situation is that the pushrod is still 100% straight, I rolled it on my glass coffee table and it's perfect, so I don't think that the valve has come in contact with the piston... thank god...

    So to my question... is it possible, and have any of you experienced a rocker arm just cracking on its own accord?

    I'm going to have my engine guru do a leak down test to make sure the piston and valves are still okay, just to be safe. Then I'll put in a new set of roller rockers, because shiny new engine parts are fun.
  2. RS1979

    RS1979 Veteran Member Lifetime Gold Member

    Jun 18, 2013
    Memphis, TN
    I've seen cheaper aluminum roller rockers crack. Your pushrod normally won't bend unless your valve hits a piston. I think your rocker just wore out. Replace it and see how it runs.
  3. connorbe

    connorbe Member

    Jul 5, 2017
    South Dakota
    Do you think I'd be okay just getting a single rocker replacement for that valve to try out and see if it fixes the issue? I wouldn't keep it that way for long, but just for the sake of seeing if that fixes the problem?
  4. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

    Nov 4, 2004
    Ringgold, GA
    Depending on what brand rockers you have. I have an old set of Crane extruded rockers that have been on since mid 90's with no issue. If these are off shore pieces, then I would replace all. It's likely a random thing but aluminum has a pretty unpredictable duty cycle also. And if you just want to check that one cylinder, you can use an old stamped rocker just to try it out.
  5. biker

    biker Veteran Member

    Absolutely. Then buy some stainless roller rockers.
  6. budro6968

    budro6968 Veteran Member

    Apr 2, 2016
    Jax Florida
    I have seen the factory stamped steel broken in two before. Just replaced and the engine ran fine. I asked if the engine was run hard and the guy said "No". My 74 C-20 Has a 454. I went to do some new gaskets for rocker covers and discovered 4 rocker ball pivots were upside down. It never made any noise and seemed to run fine. Just strange that someone put it together like that.
  7. GoldenOne7710

    GoldenOne7710 Veteran Member Lifetime Gold Member

    Jun 23, 2004
    Athens, GA
    Just to cover your bases...and for our think tank...give a few more specs. Cam specs? Compression ratio? How many miles on the parts? Valve spring rate?

    Extremely possible it's just a bad rocker. Need to cover everything so that you don't throw another rocker arm on and have interference somewhere else that causes further damage.
  8. mrdragster1970

    mrdragster1970 Veteran Member Lifetime Gold Member


    Stuff happens. I've seen $2000 rockers break, and stockers run in the 9's for a decade!!!
    Never had aluminum on a street car, but the stainless are pretty damn tough if you can afford it.

  9. CamaroGP

    CamaroGP Veteran Member Gold Member

    Nov 10, 2012
    Summerfield, Florida
    You are lucky. I have seen rockers come off the side of the valve stem and push the retainer down and drop the valve. :(
    As mentioned a decent set of rockers is a good investment. Example is a set of Crower stainless, they are pricey but I feel they are bullet proof.

    On stocker motors I like to run roller tip rockers. They are a good mid-point between full rollers and stock.
    These are what I'm talking about.
  10. budro6968

    budro6968 Veteran Member

    Apr 2, 2016
    Jax Florida
    I went to look at a 500.00 suburban with 454. One of the Valves dropped and punch a hole in the head. Unreal. The guy change his mind about selling. Waste of time.

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