336 cam ?

Discussion in 'Old's Cool' started by SprintSix, Sep 8, 2010.

  1. SprintSix

    SprintSix Been here awhile

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    Is there anyway to tell what cam you have without pulling it? Jugs are off, timing cover is coming off today. I have 2 r100s'. Both are open. One came with a few extras, 1050 kit, reworked dual plug heads, braced swingarm, fork brace. I am combining them into one good bike.
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  2. ericrat

    ericrat Long timer

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    If you are already down that far it probably easier/more accurate to just to pull the cam. But since you asked, here is what I would do if I had oo.

    Put a degree wheel on it and a dial indicator on the lifter. It would have been easier to measure from the rocker while the jugs were still on. The fact that you can't use the correct checking clearance will throw you readings way off. On second thought, it might be easier to bolt up a jug and rocker to one side.

    Here are the specs on the 336 cam.

    http://moragafalconers.org/bmw_336_cam/Sport%20Cam%20Installation%20Draft.pdf

    The specs for the stock is here.

    http://w6rec.com/duane/bmw/engine.htm

    The two cams are radically different enough that you should be ablet to tell that you have something other than stock. Do not expect to reproduce the published numbers. Google "degree a camshaft" to get a general idea of the process.

    Good luck,

    Eric
    #2
  3. bpeckm

    bpeckm Grin!

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    Thanks for the links re: 336 cam.... bookmarked, for "when and if"...

    :D
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  4. mykill

    mykill odd

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    My 336 cam is a late model for simplex chain and is stamped on its nose at the timing sprocket. Not sure how the earlier ones are marked.
    #4
  5. Sniper X

    Sniper X De Oppresso Liber

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    Aren't the lobes way wider (more duration) on the 336 camshaft, and thereby, noticeable by just looking at the lobes?
    #5
  6. bmwrench

    bmwrench Long timer

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    You can tell the 308 from the 336 by looking at them, but I have to have them side by side. There's a noticeable difference. You can also check via the dial indicating method at the lifter. Measure full lift and multiply by 1.39 (the rocker ratio) You can also get an idea by when then the motor starts pulling hard. With a 308, the motor begins making good power at about 4500 RPM. With a 336, about 5500.
    #6
  7. supershaft

    supershaft because I can

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    Cam specs are pre rocker arm ratio. Cam specs are cam specs. Valve timing specs are valve timing specs. Rocker arm ratios vary. I would measure lift at the adjuster side of the rocker arm. There is no ratio there although the radius of the arm is slightly altering your reading. It will still be close enough to know if you have a 308 or a 336. Despite many reports to the contrary I think because of one erroneous internet writeup by Tom somebody, 336's DO have more lift than a 308. I think it is a bit over 1mm.

    336's offer a lot more midrange with a lot of setups. Big port heads like the original poster's engine has can be a midrange problem. IMO, 336, late model raised port floor small port heads, 44mm intakes on STOCK seats that have the room for 2mm diameter larger valves, and 38mm mikuni's or Dells will get you a lot more than stock midrange and WAY more top end. Dual plugging and raising the compression will only make it all even better from idle on up as long as you don't go too far, especially right off idle and up through the midrange. I am running a 336, stock 42mm intake, small port heads, stock 8.7:1 CR, and 38mm carbs. I have a lot more midrange than stock. Going from 32mm Bings to 38mm Dells helped my midrange by quite a bit. I think my 336 makes more power than a 308 from about 3000rpm on. At about 5200 to 6200 it kicks in to stage two is making considerably more and above 6200 it kicks into stage three and is making a world of difference.

    I am typing all this just to counter all the 336 stuff I read that in my experience is just not true. I had to listen to a bunch of 336 horror stories while I installed mine at a well reputed dealership. ALL of them were BS.
    #7
  8. kixtand

    kixtand Long timer

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    This is interesting, and quite good to hear. I'm planning on building a new engine over the winter and was on the fence about the stock 308 v/ the 336. Sounds like the 336 wins hands down in my application...

    We may have to chat 'fore too long--

    kix
    #8
  9. wirewrkr

    wirewrkr the thread-killer

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    So let me get this straight....
    Your saying that a factory trained BMW tech with over 40 years experience and many many engines under his belt ( many race engines ) is wrong?
    Wow, my world is rocked
    Or did I just read you wrong?
    #9
  10. supershaft

    supershaft because I can

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    You read me right. Cam specs are pre-rocker arm ratio. There is no need to multiply the lift at the lifter by the rocker arm ratio. That would get you valve lift specs, not cam specs. He probably just got it backwards in his head. It is easy to do when you are thinking and writing about cam specs.

    Speaking as a factory trained BMW tech myself, everyone needs to remember that BMW service school has a 100% student graduation rate. Every time I have gone, it was made abundantly clear that if by some chance you didn't pass the tests, you could retake them until you did. I hope that tells you the same thing it tells me.

    40 years? I am really NOT talking about any inmates here since I am new here and don't know much about most everyone; nevertheless, I know of quite a few people out in the real world that have been tearing stuff up for 40 years or longer. It's like a tradition with some people. I have even seen it handed down from one generation to the next. Having said that, some of my close friends might think that my dad handed down his BMW factory training to yours truly. Not so! But he was smart enough to know that all I had to do was show up on the coattails of any dealership and it would be a done deal.

    I hope that didn't rock your world out of orbit! It's just common sense and common knowledge to me.
    #10
  11. wirewrkr

    wirewrkr the thread-killer

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    My world? Getting rocked by some noob like you?
    Not bloody likely. I was being sarcastic.
    #11
  12. SprintSix

    SprintSix Been here awhile

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    Thanks for the replies. I have one timing cover off and the second ready to pull. Visual inspection seems to indicate that both cams are the same. So unless they are both 336 cams they probably are stock. I will update as I find out more.
    #12