Interpretation of cam timing in workshop manual | FerrariChat
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Interpretation of cam timing in workshop manual

Discussion in '308/328' started by kiwiokie, Sep 9, 2016.

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  1. kiwiokie

    kiwiokie Formula 3

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    #1 kiwiokie, Sep 9, 2016
    Last edited by a moderator: Sep 7, 2017
    Sorry if this is a basic question but am I correct in interpreting the factory workshop manual page that the intake cam at 34 degrees BTDC will correspond with number one intake valve having 0.5mm lift or 0.020" ? Kind of critical and don't want to get this wrong.
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  2. Steve Magnusson

    Steve Magnusson Two Time F1 World Champ
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    #2 Steve Magnusson, Sep 9, 2016
    No, it means 0.5mm lift up the cam lobe from the base circle -- i.e., either:

    1. Set the intake valve clearance to exactly 0.5mm (by using a special thickness shim), then the "event" occurs when the intake valve first moves, or

    2. Measure the operating clearance, then the "event" occurs when the measured clearance + the valve motion = 0.5mm.

    One caution is that the angular values in the WSM are only for a particular year/version -- you should use the angular values listed in the OM for your exact year/version 308.
     
  3. kiwiokie

    kiwiokie Formula 3

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    #3 kiwiokie, Sep 10, 2016
    Thank you Steve! That is exactly what I needed.
     
  4. kiwiokie

    kiwiokie Formula 3

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    #4 kiwiokie, Oct 12, 2016
    Next question, had intake and exhaust cams degreed, went to torque cam bolt to the 80lbft specified and the exhaust cam jumped a tooth. We did not have the camshaft lock in place because I thought this was just for holding the cams while the belt is installed. Does not seem like it would hold against 80lbft? Do you torque these camshaft bolts or use an impact?
     
  5. yelcab

    yelcab F1 World Champ
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    #5 yelcab, Oct 12, 2016
    First, you get to do the cam timing all over.
    Second, if there is a flat on the cam shaft behind the sprocket, you use that.
    Third, match book cover method.
    Fourth, an impact gun.
     
  6. fastradio

    fastradio F1 Rookie
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    #6 fastradio, Oct 12, 2016
    Lock the cams in place and torque the bolts. The belt tension is not enough...
     
  7. kiwiokie

    kiwiokie Formula 3

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    #7 kiwiokie, Oct 12, 2016
    Already done the first step!
    No flat behind the sprocket.
    Will try the paper under a cam bearing method which I assume is like the match book cover?

    Don't really want to resort to the fourth option.
     
  8. kiwiokie

    kiwiokie Formula 3

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    #8 kiwiokie, Oct 12, 2016
    Hi David! Only about two years since you helped get me started on this project! Finally on the home stretch I hope. Cheers, John
     
  9. kiwiokie

    kiwiokie Formula 3

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    #9 kiwiokie, Nov 14, 2016
    Next question is timing 5-8. Most of the info I have found on the forum is for replacing belts on a running engine rather than following a complete tear down and rebuild so I have not found anything that describes the process for the right bank.

    It looks like the PM 5-8 mark on the flywheel is 90 degrees off from PM 1-4. Is that correct?

    If so, rotating the crank so the degree wheel is 90 degrees from TDC on PM 1-4 should give TDC on the compression stroke for #5? (The flywheel is not currently fitted due to clearance issues on the engine stand so I am trying to find an alternative reference point.)

    Which can then be used to time the intake and exhaust cams by attaching the dial gauge and measuring the movement in the shim bucket on #5 and adjusting the cam gear using the same process as #1?

    As always advice is greatly appreciated.

    Cheers, John
     
  10. Motob

    Motob Formula 3
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    #10 Motob, Nov 14, 2016
    You are correct on all counts. 5-8 bank TDC is 90 degrees from 1-4 bank. Use the same method you used to time the 1-4 bank on the 5-8 bank.
     

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