455 Stage 1 - Cracked rocker shaft - What would cause this?

Discussion in 'Street/strip 400/430/455' started by 2nd Gen Buick Fan, Oct 27, 2019.

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  1. Brett Slater

    Brett Slater Super Moderator Staff Member

    Would the HD shafts from TA and precise pushrod length remedy this?

    I broke close to a half dozen of these back in the day and ended up attributing it to heads that were milled a bit more than I thought.

    Adjustable pushrods from the GSCA proved to be the problem solver, although I've read a lot about them not being favored as much these days.
     
    Brett Slater, Oct 29, 2019
    #21
  2. 2nd Gen Buick Fan

    2nd Gen Buick Fan Platinum Level Contributor

    Thanks for the advice. New parts will arrive Thursday and I'll report back.
     
    2nd Gen Buick Fan, Oct 29, 2019
    #22
  3. Mark Demko

    Mark Demko Well-Known Member

    Adjustable pushrods are a dated fix anymore, much better to buy the correct length ones.
    Years ago I had a set of Adjustables, one of the adjusters snapped off in my lap, NEVER used em again.
     
    Mark Demko, Oct 30, 2019
    #23
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  4. Brett Slater

    Brett Slater Super Moderator Staff Member

    What's the best method for measuring so "correct" length pushrods can be ordered?
     
    Brett Slater, Oct 30, 2019
    #24
  5. Thumper (aka greatscat)

    Thumper (aka greatscat) Well-Known Member

    Get an adjustable pushrod and measure them all,jot down the correct length for each and determine a length that works for all cylinders.
     
    Thumper (aka greatscat), Oct 30, 2019
    #25
    Mark Demko and Brett Slater like this.
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    DigitalCaliperPRR.jpg
     
    LARRY70GS, Oct 30, 2019
    #26
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  7. Brett Slater

    Brett Slater Super Moderator Staff Member

    When measuring, what are you using as the point where you say the length is sufficient?
     
    Brett Slater, Oct 30, 2019
    #27
  8. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Use an adjustable pushrod, extend it to 0 lash. Then measure and add .050 for preload.

    PushrodMeasurement..jpg
     
    LARRY70GS, Oct 30, 2019
    #28
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  9. BrunoD

    BrunoD Looking for Fast Eddie

    The biggest problem is most likely over tightening the rocker bolts.the spacer TA sells is a big help.And lets not forget,25 pds is the most you can tighten them.I would not be surprised that what happened to this car.Bruno.
     
    BrunoD, Oct 30, 2019
    #29
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  10. Bens99gtp

    Bens99gtp Well-Known Member

    There are many company's that sell a checking pushrod, the one I have gains .050" per every turn.....so I take the length+ (# of turns×.05)

    Alot of companies sell pushrod in length of .050 so if you may have fudge the preload slightly, aiming for .050 but .025-.075 should be acceptable, I prefer to target the lower end of the range
     
    Bens99gtp, Oct 30, 2019
    #30
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  11. 2nd Gen Buick Fan

    2nd Gen Buick Fan Platinum Level Contributor

    Two new push rods, one new rocker arm shaft, eight plastic rocker arm retainer pins and she's back to normal. Oil at all 16 push rods. Mechanical oil pressure gauge reads like it did before. Drove the car for 20 miles and parked it for the winter.

    Thanks to all who chimed in on my issue!
     
    2nd Gen Buick Fan, Nov 8, 2019
    #31
    73 Stage-1, James DocRik Price, #7 and 2 others like this.
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