dougs968

Blue if it is called for, then torque to spec.

jax

Thanks Doug.

dougs968

Jax, I'm home and just checked my spare. It looks identical, so I'd say run it. Unless your number has changed I'm going to send you a couple of pics of mine from my phone.

jax

Alright I get it. When initially installed, the backing plate has a fixed postion on the camshaft because of the keyway; the Cam gear can move around a little bit relative to this as it has a larger keyway slot. What holds the Cam gear in place then? My initial assumption was incorrect. It is NOT the rotor bolts/spacer, that keep this position fixed (although when tighted I think it would help some), it is the main cheesehead bolt and washer. Apparently the pressure from this is enough to prevent the Cam gear from changing position on the camshaft.

docmirror

You have part of it. Go back to your first post, and look at 103-05, part 19 'hub'. This hub slips over the end of the camshaft, and is aligned snugly with the keyway on the cam. The cam gear is fitted to the end of the cam and hub and is designed to be held in place with both the three allen screws that the rotor comes with, and also with the large end bolt and flange lock(22 and 23).

Setting the cam timing accurately is a monstrous job that Porsche makes even harder with their crappy discussion in the WSM. It requires dual dial gauges, and lots of understanding of the text. The very short version is that the intake valve on the #1 cyl gets 0.39mm of depth using the plunge method of cam timing. Don't forget, that the driven cam is the EXHAUST, and the measurement is done on the INTAKE lobe, and the variocam has to be pressurized with air to get it to the correct location. Like I said, a monster job.

There is an alternate method that uses a shop made cutout of the cam profiles that rests on the head. This method presumes that your cam timing was correct when the assembly was taken apart.

jax

Thanks Doc. I am going to try and preserve the timing as much as possible.

As you can see in the picture...



...the cam gear is in about the middle of its adjustment range (I have kept this setting upon disassembly). Lets say I were to make changes to timing without the dials, would I notice a change in the engines performance by making small adjustments to this? How small of an adjustment would be felt?

pontifex4

I believe that you are correct: you're missing the little spacer that goes between the rotor and the gear, at least in that picture.

dougs968

I agree. I went to the extra trouble and used the two dial indicator method. As far as I could tell I was within less than a thousandth of being perfect. Checked and rechecked at least half a dozen times. That was hard enough, but the hardest thing for me was tightening the center triple square bolt on the end of the exhaust cam without moving your setting. I needed help with that. I'm not sure one guy could do it himself.

MB968

You can lock up the assembly (parts 19, 20, & 21). Replace each of the three rotor bolts holding the rotor on with shorter ones. Without the rotor in place you'll be able to put a little more clamping force on the assembly, removing one bolt at a time and fishing a shorter one under the rotor. I was able to retain my cam timing setting doing it this way.

If you have to remove the complete assembly to do the cam chain pads, etc. you can scribe the hall sensor disc before you loosen up the triple square bolt. As I recall, it is a tight fit to the key, unlike the three pronged yoke that the rotor bolts to which is a loose fit to the key to allow it to be timed. Just mark the timing belt toothed wheel, and the hall sensor disc to be able to line them up later. There are a lot of holes in the timing belt toothed wheel so it is easy to mark the one relative to the other. It won't be as good as resetting the timing with dial indicators, but by scribing the two as described will be so close to your current timing you'll never know the difference.

And as has been stated earlier, you are missing the three aluminum spacers that fit between the rotor and the toothed timing belt wheel. Make sure you buy these so you can install them when you put a new rotor on and lock down the rotor without distorting it.

jax

I've been a little disheartened by all the missing pieces I am finding as I have started doing the maintenance on this car. Missing parts everywhere!

Anyway, I have a new rotor AND the spacers, and was planning on tightening the main cam bolt by holding onto the cast areas highlighted in these photos (unless of course the experts recommend otherwise!). With the cam gear tightened against the other pieces which are fixed on the cam, that should hold it in place as the main bolt is tightened down.





Thanks everyone.

docmirror

You are correct sir. Use that to counter hold the ex cam while setting the timing. At this point, I would just make one of the profile gauges on page 15-9 of the WSM. Install the cams and chain, and fit the cams to the profile gauge made of wood. Then install the timing components on the front of the ex cam, insure the crank is at TDC and lock it all down. Put the belt and tensioner on, and roll it around twice back to TDC, recheck with the profile gauge and call it a day.

Don't forget the cams are very brittle. When putting the cam caps back on, tighten each one of them just slightly as you proceed. Snug the cam down evenly to prevent a broken cam. I also use a generous dollop of cam moly lube on assembly as well.

Are you replacing the chain? I would at this point. Roger has it in stock: 817-430-2688. He can also get all your missing bits for you as well, and ships very quickly.

jax

I suppose my neighbors are lucky, I mean if there is going to be a car up on blocks in your neighborhood for a month it might as well be a 968.

Alright, I'm ready to put the timing belt back on. After using the old belt for practice I found it quite difficult to get it in place with the tensioner pulley installed. Is this normal? That tensioner pulley was a nightmare for me to clip in, and I would not like to re-live the procedure if I don't have to. The experiences of my guiding forces would be appreciated.

Thanks.