Question about a /5 rocker upgrade

Discussion in 'Old's Cool' started by StephenB, Sep 5, 2011.

  1. StephenB

    StephenB G(/)S ... what else!

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    (Source: Antons article on Airhead Rocker Arms)

    I have a 600cc (/5) engine that I am building from the ground up. Currently, I am looking at the rocker and how to best upgrade them. The heads have the rocker post with 15.5mm outer and 10.5mm inner diamater.

    1st Question: the inner post seems to be a sleeve tube, about 26mm long which is pressed in into the head, is that correct? If so has anybody attempted to remove them?

    I have original /5 rocker arms & posts and they have pitting. I have /6 rockerarms and post from a 1974 R90S but there is pitting as well. Both sets can't be used.

    I do have a set of 1976-up rocker arms (56mm wide) and posts (16mm) which is in good and usable condition.

    2nd Question: if I could remove the 15.5mm sleeve tube (see Question 1), it should be no problem to fabricate a sleeve for the bore (about 21m OD) and press-fit the sleeve on the button-type rocker post and then the whole assembly into the head? Or am I missing something here?


    Thanks very much in advance for your insight and recommendations. I know there are upgrade sets and all, that but I like the challenge.

    Stephen
    #1
  2. bmwrench

    bmwrench Long timer

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    The post can be removed by heating the head, but unless they are later heads with the casting surrounding them, you'll have to fabricate a complete new post. A simple solution is to modify the existing sleeve at the top of the post to accept the '76-'84 rocker clamp. This works very well.
    #2
  3. east high

    east high Been here awhile

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    The rocker arms were pretty worn on my /5. Wirewrkr sells an upgraded roller bearing kit which bolts right up. You might want to contact him.
    #3
  4. StephenB

    StephenB G(/)S ... what else!

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    Fabricating a post isn't a problem, I have resources for that.

    This is the area around the original rockerpost:

    [​IMG]


    That should be enough meat to press-fit a new rocker post like this:

    [​IMG]

    This seems to be the easier solution . I like the idea of not modifying the head, just modifying the sleeve ... makes sense. Now, I don't have a sleeve in my stack, does somebody have dimensions? It should be a very straightforward mild steel cylindrical part that takes no more than 5-10min on a lathe, no?
    #4
  5. bmwrench

    bmwrench Long timer

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    Being a lazy sort, I usually modify the original /5 part: 11121254840
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  6. StephenB

    StephenB G(/)S ... what else!

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    Got one around to measure it for me?
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  7. wirewrkr

    wirewrkr the thread-killer

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    This is what I do.
    just turn it down enough to fit in the /7 rocker base.
    Works very nice. I use to modify the rocker base, but this is easier and simpler.

    Attached Files:

    #7
  8. StephenB

    StephenB G(/)S ... what else!

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    That does help! Thanks, Robert.
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  9. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    Wire, didn't see anything at your Website on the needle bearing kits. Can you give details on this?

    I have a needle bearing conversion on my /5 (which is a "late" /5 and has /6 rocker posts in the heads). Haven't had any problems with them, but they are over 25 years old and are gonna wear out sometime. The eventual repair is going to be expensive, but I'd like to keep the options open...
    #9
  10. wirewrkr

    wirewrkr the thread-killer

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    The thing to do Bill, is to get a set of rockers from a 76-84 off of Ebay for cheap. (They are much better than the 74 and 75 models).
    I don't sell them anymore because no-one wants to pay the price that I sell them for when I have them. I can't blame them, evreyone wants to get every thing as cheap as possible these days.
    Anyway, if you need the outer collars (for earlier heads with the exposed rocker supports) I will turn down your supports for $25.00. Which heads do you have?
    If your not sure how to tell, their was a thread here a few months ago with lots of pictures of the different heads and how to easily tell the diff.
    If you buy the rockers from Ebay or any where else for that matter, make sure you get a guarantee that all the bearings are intact, those stupid little things have gotten way expensive.
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  11. Bill Harris

    Bill Harris Confirmed Curmudgeon

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    That's the truth. The rocker assemblies from BMW are obscenely expensive. And the worst thing is that the needle bearings are an odd size and not "generically" interchangable with anything, so you are between the dog and the fire hydrant and can get the replacement bearings only from BMW.

    Mine are in fantastic condition, even after 25 years and some 70K miles. The shafts show only very, very light "frosting" and the needles and cages are in great shape. For the longest time I didn't ever inspect them, but about 10 years ago I did and as a rule I'll inspect them every 2-3 years, whenever I have the head off. My understanding of their failure mode is that the ends of the roller cages fail (as a result of too much rocker axial play) and the individual rollers work their way out. Or a general oil failure to the rockers (for various reasons). Otherwise, it seems to me that they should last a very long time.

    On mine, their "weakness" is that I did not keep the rocker axial play adjusted closely for a long time, and the axial movement of the rocker "pounds" the rollers against the ends of the roller cage, causing failure. So mine are flagged as "suspicious", at least to the 250K mile level. I might just bite the bullet and spring for a new set of needle bearings ( eight at ~ $25 a pop) if the rocker shafts and rocker arm tips are in great shape, doing a pre-emptive repair.

    Used parts from Fleabay are a risky option, only as a last resort.

    I briefly considered making new rocker shafts to fit "off the shelf" needle bearings, but with needing to harden the shafts and fabricate the shaft support blocks for the new shafts, this would be a royal PITA. Even for a hobby... :wink:
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  12. StephenB

    StephenB G(/)S ... what else!

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    Can somebody measure an original part for me? I have a line on 8 of those /5 spacer sleeves but I don't have an original to compare.

    Thanks.
    #12
  13. wirewrkr

    wirewrkr the thread-killer

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    Stephen,
    O.D. = 20mm
    I.D. = 15.50mm
    thickness, tallness, etc 11.5mm
    #13
  14. StephenB

    StephenB G(/)S ... what else!

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    Thanks Robert.

    Just for my clarification: the O-ring dimensions are 21 x 15 x 3mm so the spacer is not supported on the casting, it sits on the o-ring. That makes the fit between the post and the sleeve ID (15.5mm dimension) critical. If I were to re-sleeve I could introduced a tight slip fit between (1) post and ID of the sleeve and (2) OD of the sleeve and the '76-'84 rocker block recess.

    Am I making some sense here?
    #14
  15. wirewrkr

    wirewrkr the thread-killer

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    Stephen, I'm not sure what you're asking, but it sounds like you may be over-thinking it.
    #15