GregBBRD

Been watching this...to see if you figured it out.

You need to set up the dial indicator to zero, when the camshaft has absolutely no lift. By setting everything up at the TDC mark, you are probably "missing" some lift that already occurred.

Set up your dial indicator when the "base circle" of the camshaft is touching the lifter...the lobe will be pointed directly up. Then turn the engine over to 20 degrees ATDC and read your measurement. (You need to turn the engine through about 120 degrees, instead of 20 degrees.)

Make sense?

Landseer

It means you have a normal car.

In 86, Porsche had two engine platforms for 928, basically (with market crossover and exceptions) USA/Jap 32V and ROW 16V

In 1987, Porsche finally consolidated. One base "world" engine.

Thats what all S4's had.

Looking forward to you using Greg's advice and solving this and reconciling with the 32V'r! Good luck! Godspeed! Don't take any wooden nickels. Can't really help you anymore, just watching to learn.

GregBBRD

It is also important to realize that the Porsche method is an "exact" way to set the cam timing. Ken's tool is subject to any variations in production tolerances (cam gears, key location in the cams, etc) and can be off anywhere from 0-3 crank degrees, in my experience of using it and comparing its reading to the factory setup. While this may seem like a ton, it's insignificant in the running of these cars....the cams move around more than this, as the belt wears! Ken's tool works great for cam timing set-up on 99.5% of the cars out there.

aaddpp

Thanks Greg, having trouble visualizing it, but I think I am with you. When I have some free time this eve, I'll take a crack at what you suggest and see if it helps to get the measurement to match up.

Thanks,
Dave

aaddpp

Thanks Chris, will post what I do and come up with, and hopefully come to resolution ASAP.

Dave

aaddpp

Greg, I had a chance to look at the timing and check what you said. It looks like I have been getting readings that are in line with what you suggested.
I will post my photos from today shortly.


Dave

aaddpp

After a long hiatus, I had a chance to try and sort the timing issue on my car today. As a first step, I spun the motor on the starter to (i) follow through on the Porkensioner install, and (ii) see if it would help to reduce the discrepancy between the dial indicator and the 32vr.

After spinning the engine, I took a reading of the tensioner piston length, and determined that it was outside of spec. Ken calls for 2-7mm of extension, and I had ~ 7.84mm. I am not sure what to make of this, and if it is playing into the issues I am having. I should point out that my garage is about 55 F, so I suspect that could be playing into this. Also, I have a new belt on the car (Gates), though it has been in place for 2-3 months at this point.

Even though I found the spec issue with the Porkensioner, I went ahead and took readings of the timing using both methods. I think that there was some imrovement in the dial indicator readings following the spinning of the engine. Results follow below.

I think I know what I have to do at this point, but before I go ahead and mess with the timing, I wanted to figure out if the tensioner is playing into this issue, and what to do about it if so. Any thoughts? - Thanks, Dave.

Update - Additional Information: Forgot to add that a Kempf Tool reading was within spec, toward the higher side of the window.

Driver Side - Dial Indicator Method

Photos 1 & 2 showing zero @ TDC

Photo #1
http://www.flickr.com/photos/51967142@N00/5405486855/
Photo #2
http://www.flickr.com/photos/51967142@N00/5406091548/
Photos 3 & 4: At 2|0 dial indicator shows ~ 1.65mm...should be 2.0 +/- 0.1mm. Note: This figure shows improvement after spinning the TB with the starter. Prior to spinning, it read ~1.425.

Photo #3
http://www.flickr.com/photos/51967142@N00/5406091202/
Photo #4
http://www.flickr.com/photos/51967142@N00/5405486629/
Photos 5 & 6: Shows location on balancer where 2.0mm is achieved

Photo #5
http://www.flickr.com/photos/51967142@N00/5406091332/
Photo #6
http://www.flickr.com/photos/51967142@N00/5406091398/
Passenger Side - Dial Indicator Method

Photos 6 & 7: Skipped showing the zeroing here. At 1.8mm HB is still a little shy.

Photo #6
http://www.flickr.com/photos/51967142@N00/5406092166/
Photo #7
http://www.flickr.com/photos/51967142@N00/5405487565/
Photos 8 & 9: Here is the balancer within permisable range...+.1mm

Photo #8
http://www.flickr.com/photos/51967142@N00/5405487655/
Photo #9
http://www.flickr.com/photos/51967142@N00/5405487723/
Photos 9 & 10: Here is the dial gauge reading at 2|0...Shows just shy of .2mm in excess of spec.

Photo #9
http://www.flickr.com/photos/51967142@N00/5405487801/
Photo #10
http://www.flickr.com/photos/51967142@N00/5406092624/
32vr Method

Photos 11, 12, & 13: Results were similar to what what achieved in the previous test.

Photo #11
http://www.flickr.com/photos/51967142@N00/5405488067/
Photo #12
http://www.flickr.com/photos/51967142@N00/5406092936/
Photo #13
http://www.flickr.com/photos/51967142@N00/5406092774/

WallyP

Might be interesting to check TDC on #1 against the marks on the crank...

aaddpp

Hope I am answering the question properly...I rigged up a dial indicator to test that cylinder #1 reached the peak of its stroke at the same time the ballancer was at TDC. My measurement showed that the balancer was correctly aligned, so I think that I have been able to rule that out.

Dave

PorKen

The tensioner/damper piston extension is only an indicator of belt length. It should not affect a valve timing procedure.

7.84 is a bit on the outside, but may be fine as the belt has had some time to relax. A used belt will show up to 2mm more extension than a fresh-from-the-box one with a cold engine. A warm engine will reduce the extension by about 2mm. Maximum extension is just over 11 mm.

If you are uncomfortable with the measurement, you can reduce the extension by moving the T/D closer to the lever, as described on the last page of the current manual, available (here).


For best results, valve timing should be set with a belt with at least a few hundred miles on it.

docmirror

What Greg is saying, is to set the cam lobe for the lifter you are checking so the nose of the lobe is pointing straight up at you. this way, you are not taking a chance that you are on the ramp of the lobe when you set zero. It doesn't matter what the crank pointer says, so long as the cam lobe is facing straight away from the lifter, and at your face.

Now, start your plunge to 20Deg ATDC. At this point, make your cam settings as per the book, 1.8 and 2.0mm respectively. the go back an use the 32Vr tool and see if they agree. I would stick with the plunge setting, per Porsche.

I think your tensioner out of spec reading isn't important. It may be caused by the cam gears being worn some.

aaddpp

Thanks Ken. I went back and checked the length again this evening, and picked up a reading of 6.94. The garage had warmed up quite a bit, and I noticed there is slope on the lever above the piston so I was extra careful to make sure I was measuring at the center of the piston. Either way, the tensioner seems to be within spec at this point.

Docmirror, I followed this procedure, and was able to confirm zero depression as the cam lobe rotated away from the valve. I was only able to do it on the passenger side, but will try it on both sides again tomorrow to make sure I can repeat the findings. If all works out well, then I will move toward adjusting the timing via the dial indicator method.

Thanks,
Dave

aaddpp

This AM I had a several free hours and decided to have a crack at adjusting the timing. The process seems pretty straight forward, but I ran into a few issues that are probably nothing a little experience couldn't help solve. Did also want to point out that Greg's suggestion of making sure the valve is at max height turned out to work well on the driver's side - the readings seem to be within or just a bit over permissible spec. On the passenger side is did not seem to make as much of a difference.

Issue One: The dial gauge shows some variance...each time I rotate the engine 720 degrees, I will get readings that vary a bit. It interesting to note that when the the valve is up (no depression) there is very little variance...the indicator always returned to zero (@ 5mm preload) +/- 0.02mm. I am going to look and see if there is a way to add some lubricant to the dial indicator shaft to hopefully reduce some of the friction that may be making the gauge readings jump around a bit. It should be noted that all readings are now within the +/- 0.1mm spec, though some are at the very high end + 0.7-0.9mm. I feel like, if I going to do this properly, and factor in any expansion / wear, I should be closer to the specified 2.0mm setting.

The second issue I am having is when I try to set the timing - by releasing the M10 bolt and and rotating the crank until 20 degrees is reached with the valve at 2.0mm. While I can get the 2.0mm and 20 degrees to meet, the position will tend to revert back to the original incorrect timing reading. I ran out of time, so I could not check on why this is happening exactly, though I suspect the following: After loosening the the M10 bolt, I was using a wrench to hold the cam shaft...as the manual state the cams must not move. The issue I think, is that I was holding the intake cam, while tightening the M10 bolt attached to the exhaust cam. I suspect the intake cam & chain are not holding the exhaust cam in perfect position and that the M10 tightening process is causing the exhuast cam to move some - what's interesting is that the error is similar time after time, which I think could be possible if the chain slack was taken up to the same point each time. When I have another crack at it, I will use a combination wrench on the lower cam to hold it steady - not sure what size the wrench point is on the cam, but none of mine were large enough. Suspect is 24mm-26mm.

One more note on chain slack: I see it as a real possibility. One other place I have observed it - I think - is at 1.6mm valve depression on the driver side. When passing this point, the dial indicator (reading the intake valve) will consistently pause briefly, even as the crank rotates. I am guessing that slack in the chain is causing the intake cam to pause as the exhaust cam picks up any slack.

In this whole process, I am surprised the M5 bolts don't seem to be holding the position of the whole system - thought they should.

I'm going to go back and have another crack at it this weekend, but any thoughts, suggestions, or tricks would be appreciated.

Dave

Neil Forn

Get a degree wheel. It doesn't need to be anything fancy. Any protractor that is marked in degrees will suffice. You can find nice aluminum ones on ebay or at Summit for $20. An inexpensive dial indicator and base can be found from those sources or from Harbor Freight. By measuring the lift at the valve at so many degrees you can eliminate all guess work and inaccuracy. First you need to find TDC. make a stop for the piston. You can fashion one from an old spark plug with a bolt welded into the place the electrode normally goes. The bolt should protrude into the piston's path about a half inch. Rotate your engine to slightly past TDC and insert your stop. Rotate the engine backwards until the piston hits the stop. Don't worry what the manual says, a little bit won't hurt anything. You need to fashion a pointer from wire or sheetmetal to mark the degrees precisely. Mark the degrees and then rotate the engine over until the piston hits the stop on the other side of its travel. Divide the difference between the two settings. That is exactly where TDC is. Remove the stop. On the 928 I find it easer to rotate the the engine to the point where the cam follower reaches the prescribed lift and hold the cam in that position. Then I loosen the cam bolt and rotate the engine to the proper degree setting. Lock everything down. Rotate the engine a few times and check your work. Repeat on the other side.

If you follow this procedure you know exactly where your cams are set. All differences in the harmonic balancer, castings, gears, extra are eliminated. No more guessing.

docmirror

Neil, this is what he's doing already. We have degrees marked on the damper, and he already has the dial indicator and stand.

Dave, I think you're going a bit too **** at this. If you need to go past the setting a bit then tighten the cam, you may find it works out when you rotate it.