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Sheared rocker stud?

Discussion in 'The Garage' started by dremu, Sep 8, 2005.

  1. dremu

    dremu Officious Thread Derailer Premium Member

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    My bigblock was making Bad Noises the other day, and a brief visual examination (i.e. I opened the valve cover, scurred to see what I would find) ... revealed that #1 exhaust rocker was very dark and covered in burnt gas crap, and finger-loose. The others were fine. :what:

    Going to tighten that rocker, I discovered that the top 1/4" or so of that stud was sheared off and hanging literally by a thread. :doah:

    So I got another stud, put it in, and adjusted the rocker until it stopped clattering and all is apparently well and good. My concern is, what the heck would shear a stud that big? Just the rocker being REALLY loose and being whacked back and forth?

    And :deal: is there anything else I should worry about ... the rest of the rockers on both sides looked fine and didn't seem to want more adjustment, so I left them be and sealed them back up.

    -- A
     
  2. rumbly truck

    rumbly truck 1/2 ton status

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    Was the ball and rocker burned or galled?
     
  3. dremu

    dremu Officious Thread Derailer Premium Member

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    Not galled or even scratched, really ... burned, only like the inside of a carb is, covered in burnt-gas-goo. I cleaned it with some Engine Brite and it looked fine. The end of the pushrod was nasty, maybe the last half-inch or so, but same thing, cleaned right up.

    You know, I say it was #1 exhaust ... maybe the BBC is different from an SBC. It was the forwardmost rocker for #1.

    -- A
     
  4. dyeager535

    dyeager535 1 ton status Premium Member

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    I sheared a stock stud on my brand new bone stock (well, higher rate springs) Vortecs with less than 2000 miles on the motor.

    I was *told* that the failure was a fluke by the machine shop, and appeared to a well-learned person to have resulted from the stud getting too hot when the threads were being cut. Made sense to me since the machine shop had never seen a failure like that. The stud sheared off into a perfect pencil tip, (the remaining stud looked exactly like a sharpened pencil) the other piece of the stud perfectly fit the point.
     
  5. rumbly truck

    rumbly truck 1/2 ton status

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    Was the ball or rocker blued? if it was, you might want to change the rocker arm, and pivot ball. If you do, pull the intake rocker off that cylinders intake. Install the intake rocker and ball on the exhaust. Then put the new parts on the cooler running intake position. The new parts will burnish and breakin in that position. Was the stud broke above the adjustment nut, or above it? bigblocks are hard on the valve train, look at the angle the pushrod comes at the rocker arm. Is this a hp or factory cam? You did change the oil, didnt you?
     
  6. wildmanben

    wildmanben Newbie

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    just the looseness and wobbling around is enought to break the stud. also all the heat from the friction too.
     
  7. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Aaron,


    Remember that pic of my truck on the side of the highway (from Moab) with the beach umbrella propped in the open hood....?

    That was a broken rocker stud.

    Drivers side, one of the middle ones IIRC. I swapped them all out for some ARP ones and it's been fine since.

    My BBC has never oiled right though....I've blued the rocker ball washers badly and had to replace them before too. No signs of any restrictor plugs to the top end, but even after a fresh rebuild the engine simply won't push much oil into the heads.... just a slight drizzle from the rockers at idle. :dunno:
     
  8. rumbly truck

    rumbly truck 1/2 ton status

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    It should push oil to the inner fenders. If you have that little, maybe its for some rollers.
     
  9. Blazr77400

    Blazr77400 1/2 ton status

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    I had a similar problem. I didnt break the stud, but the rockers were making alot of noise. Popped the valve covers off and noticed a few of them were not oiling very much. I adjusted one and it started oiling, messed with the other one but it didnt help. I had a second set of stock heads sitting around and swapped one of the rocker arm assemblys from it and it started oiling correctly.
    What ended up happening was the ball wore a perfect sphere into the rocker and the two surfaces sealed the oil from coming out.
    Does that make sense?
     
  10. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    I don't think that's how the oil travels...?


    The oil comes up through the pushrod tube and ends up coming out through a small hole in the rocker tip....then gushes and squirts everywhere else (this is scientific-speak, btw) the ball washer is on the rocker stud and below the rocker arm itself. I believe it's only oiling comes from whatever oil seeps down from the rocker valley (stamped rockers) and past that retaining/lash nut.

    :dunno:
     
  11. Russell

    Russell LB7 Tahoe Status Premium Member GMOTM Winner

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    Yep, thats how a small block oils anyways. I dunno about a big block.

    My 355s both have a significant amount of oil pouring off each rocker at a 500 rpm idle, if you go about 700, the rockers sling the oil off, and all over my fenders etc. Then again, my trucks all have high volume output oil pumps, that peg my oil pressure gauges at an idle when cold, then only come down to about 50 PSI at an idle.
     
  12. dremu

    dremu Officious Thread Derailer Premium Member

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    Hmm. This is starting to worry me... I may need to bring an umbrella a la Greg!

    I know the engine is a bit low on oil after this fiasco and I'll be changing the oil today. However, I did notice that, while the rockers were oily, there was NO spray when I had the covers off and the engine running. Based on what y'all are telling me, I'm a bit scurred.

    I also note that this truck confuzzles me... when she's first warming up, the oil pressure is crazy high (pegs the mechanical gauge at 60+ PSI) and then once she hits cold idle, drops to a more reasonable 15ish.

    Should I fear blockages in my oil passages, and start thinking about whatever the equivalent of castor oil is to free engine constipation?

    -- A
     
  13. Blazr77400

    Blazr77400 1/2 ton status

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    I was up a little late last night. I was confused. :confused: The pusrod actually wore a perfect sphere into the rocker arm. Then it impededthel flow to the ball.
     
  14. perp

    perp 1/2 ton status

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    check your spring clearances. if the lift is too much for the spring, the spring can stack solid and bust parts. a friend of mine had them start stacking solid after about 6 months of running, eventually it started cracking the retainers.
    just something to consider.
     

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