Airhead Rocker Arms

Discussion in 'Airheads' started by Bill Harris, Nov 25, 2011.

  1. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    I'm getting ready to finish up the top end work (vales and rings) on the R60/5 and the one item that I've just found worn that aren't being replaced at this time are the rocker arms. Specifically, the tips of the rockers that contact the valve stems. They are all pitted or galled, slightly to moderately. I think they'll last a few thousand miles, but I'd better start thinking on repair. I suspect that "repair is by replacement"; since the tip is hardened, I don't think it can be welded and reshaped.

    My /5 heads came as the early /6 style, and I was able to retrofit the "newer" early /6 needle-bearing rocker arms several years ago. The second item on Anton's Rocker Arm page:

    http://largiader.com/tech/rockers/

    Suggestions? New is horridly expensive, used is a pig-in-a-poke.
    #1
  2. Xcuvator

    Xcuvator Justa Venturer

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    I haven't looked lately, but I used to see rockers all the time on eBay and IBMWR. Are you sure you want to beat up your fresh valve stem surfaces? If it were me I'd replace the rockers before start up.
    #2
  3. Max Headroom

    Max Headroom lost in the '70s

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    I had a similar problem several years ago with an R90/6, and I got them built up with Stellite and reground. Arguably better than the parent metal. A competent reconditioning shop should be able to take care of them for considerably less than the cost of a replacement set. Just a thought . . . .
    #3
  4. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    They're not badly galled enough to wear things out right away, though I will look at the old valve stems to see exactly how they were wearing. That will define the course of action.

    I'll check with my machinist and see abouthaving the rocker arm tips stellite-faced. Recommendations on "reconditioning shops"? I'll check with Vech at Benchmark since this is a problem that /2's likely encounter.
    #4
  5. disston

    disston ShadeTreeExpert

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    Biil,

    You are the machinist. More of one than I am, I'm sure.

    I would think it would be simple to grind the tips, even by hand, I'm always thinking I can do stuff by hand but I'm probably wrong about my method, and Chrome them. The hard Chrome not the shinny Chrome. Or Nitride. Or even re-harden them.

    I have found newer rocker arms on Ebay. I will only buy stuff there that has a good picture of critical areas. The wreckers are jacking up their prices but an individual with lower prices come through now and again. Of course this takes time and a little luck.

    Charlie
    #5
  6. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    This is going to be a sticky problem to solve. New rockers are in the $60-$90 each price range. If you get a set of used rockers, there is the added concern of having used needle bearings of unknown history, at $50 a pop per rocker arm.

    Welding and recontouring is tricky and needs to be done by someone experienced. The tip of the rocker arm is a complex, compound curve and needs to be that way to contact the valve stem properly and cause the valve to rotate, as designed. If not done correclty, it may self-destruct in a few thousand miles.

    OTOH, one option is trying to re-use the old stock bushed /5 rocker arms that inexplicably had the bushings fail in 1980 at 30,000 miles. I never figured out why, but the bushings wore and also took out the rocker IDs and the rocker shafts. They were replaced by the current needle rockers. Being a packrat, I still have them and plan to take a look.

    Sometimes it's hell being a nut for attention to detail...
    #6
  7. JPSpen

    JPSpen At Large

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    I think I'd just spring for the new rockers and be done with it...

    In my experience, Screwing around with some thing and trying to make do has always cost more in the long run...

    Good Luck

    John
    #7
  8. wirewrkr

    wirewrkr the thread-killer

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    Bill, just get a set of 77-83 rockers off of fleabay and run them. They are the ones with the hardened tips.
    Then just modify your stand-offs and they fit right on. Been doing it for years, If you watch. they can go cheap on fleabay.

    Attached Files:

    #8
  9. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Buy new??? Awwww, half the fun of an old airhead is obsessing over details. :D

    Now that sounds like a plan. The early /6 heads (which mine has) can be upgraded to the '76-'84 rockers, so that will be do-able on my /5.

    Do you have dims on those adapter buttons? Or, better, do you sell them? I'm guessing that their ID is 15.5mm and the OD of the top shoulder is 18mm and the height is whatever that of the existing /6 button is.

    Piece o'cake.
    #9
  10. wirewrkr

    wirewrkr the thread-killer

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    I just modify the existing sleeve to fit in the recess in the rocker arm support.
    BUT, since you have the late heads, you don't need to even worry about the sleeves.
    #10
  11. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Ah, that's more better. I was thinking that those sleeves took the place of the /7 adapter buttons, which fit into the indexing cutouts in the bottom of the /7 rocker blocks, providing good alignment. It might be nice to make "indexing sleeves" for the early /6 heads, but it's not that big of a deal to squeeze the /5/6 rocker blocks and set the axial play when torquing the heads. Simpla Fi and all that.

    Here is the plan: I'll go ahead and use the existing rockers to get this project running. Look for a set of the /7 rockers on fleabay and IBMWR etc and replace the rockers by 1000Km or 600Mi, when I'd retorque the heads anyway. Or at least ASAP.
    #11
  12. bmwrench

    bmwrench Long timer

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    I reground many rockers from /5 up when I was the head guy at Bob's BMW (Hmm..that doesn't sound good does it?) AFAIK, there was never a problem with this repair. Most valve grinders have an attachment to grind rocker tips.
    #12
  13. Wirespokes

    Wirespokes Beemerholics Anonymous

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    I'm curious if this damage is due to an overly large gap? Will the rockers last a 100K if properly gapped?
    #13
  14. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Not in this case-- I typically keep the valve lash at .006 In/.008 Ex.

    In 2008 I pulled a couple of studs and removed the heads/cylinders to assess valve/ring wear and "decoke". At the time I was more interested in the rocker needle bearing and rocker shaft condition and, sloppily, may not have paid enough attention to the rocker tips. I have many photos of the needle bearings but only one of the rocker tips-- Right Ex, and it looks unchanged over 30K and 3 years. I probably looked at the other tips, but I can't say for certain.

    Back in the day, we used to regrind rocker tips, too. Reshaping was my first thought, but the tips need to be hardened to last. Although I'm on the hunt for a used set of /7 rockers, resurrecting these is on the mind of this DIYer...
    #14