Article and Photos by Rex Chalmers - continued from Page 1
Now for the tricky bits. First verify that the engine is at TDC #1 and that the paint marks you made on the cam wheels and distributor still line up with the reference marks you painted on the head. I always remove the cam covers and confirm that the timing marks on the camshafts line up with the marks on the cam caps. Yes it takes a bit of time, but it is well worth the effort (See Photo 1 and Photo 14).
This next section is taken pretty much verbatim from Centerlines instructions:
Install a new timing belt, paying close attention to the timing reference marks made earlier by double checking the alignment of all marks. Start by placing the timing belt over the crankshaft pulley. Next, work the belt onto the other pulleys in a counter clockwise order, allocating all the slack in the belt for the length between the crank pulley and the auxiliary pulley. Double check that you did not disturb the top dead center position of the crankshaft and that you engaged the appropriate teeth of the cam drive pulleys. Use great care so as to maintain proper cam timing. On Milano and GTV-6 models you must properly index the auxiliary drive pulley to maintain the proper ignition timing.
Important note: the new style tensioner has a temperature sensitive switching device. It is important that it is only adjusted on a cold engine and when the workshops ambient temperature is between 59 and 96 degrees F. (15-35 deg. C)
With engine cold and positioned at top dead center, loosen both tensioner-retaining nuts. Insert a 3/8 square drive into the lift square of the tensioner and rotate the assembly counter-clockwise n (into the drive belt) until the pointer aligns with the reference mark (See Photo 15). Do not use excessive force! Too much force may damage the clutching mechanism!
Holding the tensioner in this position, lock down the tensioner by tightening the adjustment nut to approximately 15 ft.lbs.
With the tensioner set in this way, rotate the engine clockwise at least four crankshaft revolutions to seat the belt. On the last revolution, line up the TDC marks. Do not back up the engine at any time. If you accidentally pass TDC, keep going and bring it around again.
Do not allow the tensioner to release tension on the belt, or you will have to back to the start of the belt installation steps. While rotating the engine, it is normal for the pointer to oscillate slightly to either side of the mark. What is important is that the pointer is aligned with the reference mark at TDC (See Photo 16). (Note that because of the angle this picture is taken at the pointer appears to be slightly north of the center of the alignment mark) If the pointer backs off past the mark (See Photo 17), increase the tension until it is aligned with the mark again.
Tighten the adjustment nut and the tensioner pivot nut to 20 ft.lbs.
Rotate the engine several more times in a clockwise direction. Line up TDC on the crank pulley. Now verify that the cam timing and #1 position of the distributor are correct (See Photo 18).
You may find that the cam timing marks on the cams and cam caps may be off slightly. As a rule of thumb, if they are off more than the width of the scribe mark on the cam, its a good idea to adjust the cam timing. Unfortunately, Alfa didnt design in any provision for adjusting the cam timing. The only safe method that I am aware of is to adjust the timing with offset keys in the cam. Stuart at Sperry Valve Works (562-988-5960) provides offset keys in several sizes. Having the cam timing correct will help the engine run smoother and provide maximum H.P. Once you are certain that you have the cam timing correct, make permanent reference marks on the cam pulleys and cylinder head so it wont be necessary to pull the cam covers next time the timing belt requires changing.
For those of you, who need more visual aids, contact our friends at International Auto Parts (800-788-4435) and order their V-6 belt tensioner video on CD-ROM. It is part number 10112.
There are, as always where Alfas are involved, differences of opinion concerning optimal belt changing intervals. Personally, I recommend to all my customers that the belt and tensioner be changed every 3 years or 30,000 miles, whichever comes first. Alfisti have told me that my chosen interval is too short. That may be, but changing the belt and tensioner is cheap insurance compared to the price of cylinder head rebuilding!