Section 15 page 102 of 16v workshop manual. Cam Timing

JD159 · 10-19-2014, 07:31 AM

Hi all,

In the process of learning how to dial in my cams. Just need a set of dial gauges but doing some preliminary homework first.

In the digital copy of the manual I have, I am missing page 102 of the procedure. I am not sure if it has anything imperative that I am missing or information that someone else can provide.

I have read that once tdc on the crank has been found, you rotate the engine 45 before TDC so that camshaft installation is safer. Then you position the cams at tdc, then move the crank back into TDC. From there you follow from step two of the procedure outlined in the manual using the dial gauges.

Is that correct? Or can I find tdc on the crank, then install the cams without moving the crank. Does the crank have to go back 45 degrees before cam installation?

Also, because of my cam's the timing is adjusted so that it is slightly advanced. How do I go about accurately setting that advanced timing on the gear? Is it as simple as once I have dial in the cam's to spec, loosen the three temporary retaining bolts and then rotate the engine counter-clockwise until the cam gear is slightly advanced?

Thanks!

guru944 · guru944's Garage

Jd159,
Which cams are advanced or retarded? The next tooth on cam
gear is 9 degrees from basic OEM tdc. Most guys will to exceed 4-6 degrees. Remember this is an interference engine. I would recommend on looking at the 968 can specs and various setup for more guidance. Remember those big valves... Later...

944 Ecology · 10-19-2014, 11:03 AM

Page 102 only shows you how to identify that the crankshaft is at TDC on #1 cylinder.

I would not retard the crank timing in order to install the cams; that procedure is more a process for the SOHC engines, Use the factory method of setting the coarse setting for the DOHC camshafts that is documented in the manual.

BTW, that procedure is only a coarse adjustment. You might find that with the cams set that way develops no power at 4000 rpm. If that is the case, you will need to adjust the cams up to +/- 5 degrees until the engine develops power properly, and idles smoothly.

JD159 · 10-19-2014, 11:52 AM

944 ecology, exactly the answer I was looking for. Based on my cams shifting the timing a little advanced helps to bring the power band into a more usable rpm range. So I'll set the timing as per the manual, and them to advance it slightly when I reach the maximum piston travel towards the end of the procedure, I will keep rotating the engine sligthly to shift the sprocket favoring the advanced side of the woodruff key.

When using the dial gauge to find the highest point of the piston, what do I look for on the gauge? If it begins to go back down I would have already past the peak, and the manual states do not rotate opposite of engine rotation. Can you expand on that part?

944 Ecology · 10-19-2014, 02:34 PM

Quote:

Originally Posted by JD159

When using the dial gauge to find the highest point of the piston, what do I look for on the gauge? If it begins to go back down I would have already past the peak, and the manual states do not rotate opposite of engine rotation. Can you expand on that part?

Watch the dial indicator as you turn the crankshaft and turn the gauge bezel to zero it when the motion is approaching, then reaching its maximum travel. Then continue to rotate the crankshaft as the needle again approaches the zero mark.

Of course, since this is a coarse adjustment, being off by 5 degrees or so is not all that important. As a matter of fact, I have never used the dial indicator method to set the timing, just got it close, checked it by manually rotating the crankshaft through several turns (to check for interference), then set to the task of fine timing the camshafts.