My timing chain was rattling, so I removed the tensioner to switch it out, but I forgot to set the crank pulley to Top Dead Center. I also rotated the crank pulley in order to get it to TDC without the tensioner in place, which caused the timing chain to skip at least one cam-sprocket tooth. Eventually the motor came to a point where it was binding and I was no longer able to rotate the crank manually.
When I continued to rotate the crank manually to bring it to TDC, I could hear the pistons make contact with valves. Eventually, the motor was binding ( I have been told), so I cranked counterclockwise to find TDC.
I looked at the cam sprocket keys (dowels), and they were slightly off to the left, but evenly so. The FSM says they should be pointing to "ABOUT 10 and 12 o'clock", so despite being a touch off to the left, it did not seem wrong.
The cam lobes for cylinder 1 were pointing away from each other, Intake to 10, Exhaust to 2. I found this a little odd, given almost every comment I have seen says the lobes will point away 180 degrees away from each other symetrically. Mine were facing away from each other symetrically (10 and 2 o'clock), but not 180 degrees opposite each other.
I also realized there were only 18 chain link PINS between the two marks on the cam sprockets, which together with the binding convinced me the chain had skipped at least one sprocket tooth. But which sprocket? I had rotated the crank both clockwise and counter-clockwise.
To correct this binding, I set my crank pulley to TDC and pulled of the intake cam sprocket and positioned the chain so that there would be 20 pins instead of 18 between the two sprocket marks. I did not remove or turn the cam from it's "bed" of cam caps.
I then re-fastened the cam sprocket bolt and torqued it to spec.
Now there are 20 pins between the two sprocket marks, the sprocket keys are slightly oriented towards the left of exactly 10 and 12 o'clock, BUT the Intake cam lobe points to 9.5 and the Exhaust cam lobe points to 2 (imagine the numbers on a clock).
Is this difference in cam lobe position normal? If not, how should the cam lobes on cylinder 1 be facing? Please use the numbers on the face of a clock to describe their orientation.
Do the cams need to be rotated individually to correct the difference in orientation?
I have adjusted the cams so that the dowel keys are at 10 and 12 o'clock, and so that the lobes on cylinder 1 are pointing outward, away from each other, symmetrically. This way provides for 20 chain-link pins to be between the indentations on the cam sprockets.
Here is an odd detail that had me confused for a while.
My SR20DE was manufactured in February of 1991 and has a crank pulley with 6 marks on it, not 5 or 7 like www.se-r.net shows it having. About Ignition Timing
I had seen many folks saying that to be at top dead center the crank pulley should line up on the SECOND mark from the left. I did that, but the dowel keys on the cam sprockets didn't appear to be at 10 and 12 o'clock, and the screwdriver in cylinder 1 seemed to reach its highest point before the indicator on the timing cover pointed at the second mark.
I was convinced that the second mark was TDC, but in fact, when I put the crank pulley on the second mark, it was actually at 5 degrees, not 0 degrees BTDC.
This was due to the difference in crank pulleys Nissan used. From the 1991 Technical Bulletins, Beginning with April 1991 production, the ignition timing mating mark has been changed as shown below.
NEW marks at -5,0,5,10,13,white paint,15,20 B.T.D.C..
OLD marks at 0,5,10,15,20 B.T.D.C..
I am not sure why my crank pulley has 6 marks on it, instead of 5 or 7 as shown above. It does NOT have any white paint between marks and the marks are all evenly spaced apart.
Because the car is pre-April 1991, I am assuming the pulley corresponds to the older version that begins with ZERO. This also makes sense when I look at the dowel keys on the cams. When the indicator points to the first mark on the crnak pulley, the dowel keys are at 10 and 12 o'clock, and the cam lobes are most closely resemble the lobes in the JWT photo at the bottom of that pdf.
If the timing is off yet the dowels are in the correct orientation, the crank pulley is likely to have spun on its rubber ring (which deteriorates with age). Go to 10:42min for a bit of good information. 10:42min - 12:30min, and 15:52min shows the example of a spun crank pulley and the timing being off. Finding True Top Dead Centre