Quote:
Originally Posted by Jazzenco
Hi everybody,
(3)I'm experiencing with timing problem of my M116.980 engine. After replacing my original camshafts which has code number 46/47 with 52/53. Engine started running unstable at idle. When I move distributor to advance position,engine become more stable, if I move retard position engine becomes unstable.
Therefore,when I check valve timing specifications of Camshafts 46/47 and 52/53 I realized that they have different timing values,
For camshaft having code 46/47,
Inlet Valve opens BTDC at 19 degrees closes ABDC 53 degrees,
Exhaust valve opens BBDC 42 degrees, closes ATDC 20 degrees
For the the camshaft 52/53,
Inlet valve opens BTDC 26 degrees and closes ABDC 44 degrees,
Exhause valve opens BBDC 60 degrees and closes ATDC 14 degrees
So, could you please tell me why there are 3 different camshafts each has different valve timings for M116 3.5 engine.
(2)Secondly, Can I correct my current valve timing values which 52/53 currently installed to 46/47 by replacing woodruff keys with specific offset to each camshaft gear? If so, could you please tell me offset value?
(1)Finally, according to the valve timing values, which camshaft provides more compression? (If available, or any relation)
Thank you very much for support and information in advance..
Regards,
Kutluhan
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(1) The 52/53 cams will yield greater compression pressure, by virtue of the earlier closing point of the intake valve, and hence more degrees of crankshaft rotation before TDC.
(2) Retarding the 52/53 cams by 6-8 degrees of crankshaft angle will bring them closer to the 46/47 timing, however there will be a slight loss of torque.
(3) Try setting the idle ignition timing by this method:
Connect a vacuum gauge to a fitting that goes directly into the intake manifold. Disconnect any vacuum lines from the distributor. With the engine idling, rotate the distributor to the position that yields the greatest vacuum reading on the gauge. Check that total mechanical/centrifugal advance does not exceed about 36 degrees (without vacuum).
The cam timing figures which you have provided are for seat-to-seat valve movement. The figures that are commonly used for comparison and for adjustment are those obtained with the valve 2mm off the seat.
In the case of 2mm valve lift, 46/47 inlet duration is 192*, 52/53 inlet duration is 190*, and both have exhaust duration of 194*. Cam centerline angles are: 46/47 > 104*, and 52/53 > 106*.