cam timing advice for first rebuild needed | FerrariChat

cam timing advice for first rebuild needed

Discussion in 'Technical Q&A' started by bertspeed, Apr 13, 2013.

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  1. bertspeed

    bertspeed Formula Junior

    Sep 19, 2009
    308
    Ive never done this before so please excuse my dumb questions.I am just putting back together my 2.0 dino engine and need to check the timming is correct.The cam cap marks dont line up perfectly with the cams.The tdc is correct with the notch on the front pulley and all the valve clearances have been set.Am I correct in thinking that the diagrams showing the cam durations refer to a rotation of the crank.And how can I precisely when the valves start to open/close.
     
  2. 2dinos

    2dinos F1 Rookie

    Jan 13, 2007
    3,056
    Wow - Crikets??

    Yes: Cam duration is always given in crank degrees. I suggest a degree wheel, a nice dial indicator and patience. I'd also suggest studying lobe center methods for setting the cams. You're at the heart of Ferrari engine tuning. This is where you get the "recipe" right for your engine and extract what was achieved back on the dyno at the factory. Off by a "little" (2 degrees), and further tuning gets fussy, more than that - real fussy. Wildly off ----- let's not discuss that.
    Below is a quick internet find on cam timing. Most of this relates pretty well. http://www.motorcycleproject.com/motorcycle/text/lobectr.html

    Also, I'd suggest checking out the Dino 246 shop manual, and the guys at Superformance know the Dino motor frontwards and backwards.
     
  3. Motob

    Motob Formula 3
    Professional Ferrari Technician

    Nov 11, 2003
    2,387
    Frederick, Maryland
    Full Name:
    Brian Brown
    The cam opening and closing timing is listed in the manual in crankshaft degrees. You need to mount a degree wheel to the crankshaft, and accurately locate TDC using a piston stop or dial indicator. You cannot rely on the notch on the front pulley. The marks on the cams are only suggestions for initial installation and cannot be used for accurate timing of the cams. The closing and opening figures in the manual are for a valve clearance of .5mm (.020"), so you have to readjust the valve clearances on the cylinders that you are using for cam timing to that spec. The mark on the pulley is PM 3/4, or TDC on cylinders 3 and 4. When one is on TDC compression stroke the other is at TDC on overlap. The way to check when a valve is opening is to rotate the valve bucket with a little pick in the notch in the bucket as you turn the engine over. When the clearance had been taken up, the bucket/shim will stop rotating, and you know that the valve is just starting to open. Use the reverse of the same method for valve closing. When the cam just starts to unload the shim, the bucket will free up and rotate. Using the vernier holes in the cam sprockets, you should be able to get the timing within 2 crankshaft degrees.
     
  4. bertspeed

    bertspeed Formula Junior

    Sep 19, 2009
    308
    Thanks very much for this excellent advice.As the cam marks were off quite a bit I would expect to see quite an improvement.
     

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