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Timing belts and camshaft help revisited

Discussion in 'Technical Q&A' started by Gianluca, Feb 7, 2004.

  1. Gianluca

    Gianluca Formula Junior

    May 6, 2003
    349
    Centreville, Virgini
    Full Name:
    Gianluca Chegai
    I just finished installing the sinistra (5-8) camshafts and timing belt.
    Everything went fine and it looks good and properly timed.
    Now, please, picture this: I had all 4 camshafts out so I aligned the PM 1-4 mark on the flywheel and aligned the marks on the camshafts with the mark on the caps. The PM 1-4 mark on the flywheel, however will show up 2 times before the camshafts re-align with the marks (2 crank rotations for 1 camshaft rotation) which means that:
    1) it is good.
    2) it is wrong as the flywheel should be moved 180 degrees
    3) as long as the above mentined marks align, it does not matter and thus is good.

    I have 66.6 % that the job is good. Will Murphy rear his ugly head again?

    By the way, in case it does, in fact, matter how do I know if the flywheel is 180 degrees off?

    Thanks.
     
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  3. ferrarifixer

    ferrarifixer F1 Veteran
    BANNED

    Jul 22, 2003
    8,520
    Melbourne
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    Phil Hughes
    err.....Read up on 4 stroke principles!

    You're good to go!
     
  4. Gianluca

    Gianluca Formula Junior

    May 6, 2003
    349
    Centreville, Virgini
    Full Name:
    Gianluca Chegai
    Thank you.
    Still little wet behind the ears in this new-found activity...
     
  5. Steve Magnusson

    Steve Magnusson F1 World Champ
    Lifetime Rossa

    Jan 11, 2001
    19,472
    Texas
    Full Name:
    Steve Magnusson
    As long as you're talking about only one bank it doesn't matter.

    Maybe you just mis-spoke, but I think your question should be: "is it possible to have the flywheel off by 360 deg", not 180 deg (if you were off 180 deg, the flywheel would not be at PM1-4).

    When you do the 2nd bank you need to have those cam marks align on the same crankshaft revolution at PM1-4 as the first bank (i.e., having one bank's cam marks line up on one particular revolution at PM1-4 and then have the second bank's cam marks line up on the next revolution at PM1-4 would be bad;))
     
  6. Gianluca

    Gianluca Formula Junior

    May 6, 2003
    349
    Centreville, Virgini
    Full Name:
    Gianluca Chegai
    Steve, you are right. I did mean 360 degrees. I am aware of all the marks must align on the 1-4 PM mark.
    I have been so focused on getting the job done without screwing up that I got a bit lost and forgot about turning the crank twice to make the marks re-align on the camshafts.
    I almost s... a brick once I turned the crank once and there were NO marks on the camshafts!
    Now it all makes sense. (four stroke principles as Ferrarifixer mentioned...)

    Thank you all.
     
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  8. ferrarifixer

    ferrarifixer F1 Veteran
    BANNED

    Jul 22, 2003
    8,520
    Melbourne
    Full Name:
    Phil Hughes
    !

    I used to look after a particular factory "sprint pack" equipped 308 in the uk.

    The factory had put the marks on the 5-8 bank cams 180 out....ie.....one crank revolution.

    All that happens, is the firing order for that bank is messed up and loads of popping and banging after a cams out job.

    Soon diagnosed and rather than swap the ign leads around to do a quick fix, I did actually re-mark the cams correctly for the future!

    Interestingly,(?) the 355 and 360 now use the 1 8 3 6 4 5 2 7 firing order instead of the 1 5 3 7 4 8 2 6 of the 308 series. (1342 per bank like a conventional 4 cyl).

    f
    8 1
    7 2
    6 3
    5 4

    Don't really know why, makes very little difference to anything, vibration would be the best theory or exhaust scavenge, but 360's vibrate worse than anything else and sound crap! So they made it worse.
     
  9. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    6,997
    Groton, MA
    Full Name:
    Verell Boaen
    NOT TO WORRY:
    As long as all 4 cams & the crankshaft's marks line up every other rev. the engine will be properly timed.

    There's only a niggling detail that might tell you it's 360 off, and it's almost impossible to see if the cam covers are on.

    The timing drive gears have a small notch that lines up with a corresponding notch in the timing cover. I think that when the crank is 360 out, the notch is pointing straight down instead of straight up.

    When I had to replace my timing drive bearings a couple of years ago, I very carefully aligned up all the marks & locked the crank in place with the parking brake. Took photos of the cam gear pins, marked both the cam & drive gears prior to dis-assembly.

    When I had everything apart I realized that the drive gears & housing had alignment notches. Marked the notches to make them visable. Blew my mind when I just couldn't get the notches to point straight up even tho with the crank was on PM1-4. The marks on the jack shaft gears were aligned with each other tho. They drive gears were always off by about 1/3 belt tooth. However, my pre-disassembly marks would line up when the drive gear notches were 180 out.

    Finally decided that either the cams & engine were aligned with the crank 360 out, or else the cam gear notches were cut 180 out. Anyway, I knew the cams were properly timed & the engine was running great prior to disassembly so I just went with the original drive gear alignment. Still runs great 2 years later...
     
  10. Gianluca

    Gianluca Formula Junior

    May 6, 2003
    349
    Centreville, Virgini
    Full Name:
    Gianluca Chegai
    Verell, I too realized (too late) tha the driving gears had notches that should point up. When I reassembled the case, I disregarded the notches completely so now the point at random points. The driving gears cover went back on fine and the gears where as titght as a duck's a.. and everything feel nice and smooth. I should have put them back the way they came out but I think they should be fine the way they are.
    Hope by the end of March to have the car back on the road.
     

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