PorKen

Then the mistake has been repeated more than once. This is why it is best to center the rotor holes in the slots if they've been max'ed out one way or the other - "for the next guy".

BTW, hopefully you are running GT chips or better get it SharkTuned (or ask around for someone else's S3 conversion chip) as those cams are much different than S4. (GT cams are S3 with a 110 LSA vs. S3 114)

Bulvot

All I know on that front is that a reputable Porsche 928 shop did the conversion. I don't know if they changed the chips or the tune. But, they have a very good reputation and the previous owner paid a lot for them to work on it. So, hopefully it has everything that it needs.

FredR

No idea why you cannot find it but from memory it is something like 49 ft lbs- doubtless someone will confirm that for you.

Just for purposes of clarity it is assumed that when timing the cams you will be working on a cold engine

Bulvot

Thanks. A torque table would be really handy. Anyway, yes, this is all happening with a cold engine. I won't even start the motor up until this and several other things are finished.

soontobered84

Ask, and the door shall be opened. Courtesy of Andrew Olson and Rob Edwards

Bulvot

Thank you! That is a tremendous help!

Bulvot

The new belt is on and the timing is set. I positioned the driver's cam gear one belt tooth off from where it was with the old belt, which put it pretty close to zero. I then adjusted both sides so that they read 0 after I rotated the engine several times by hand. Hopefully that's correct, since things are almost back together now. The cam shaft bolt holes are now pretty well centered in the slots on the gears on both sides. I can't believe that the drivers side was off by so much. I look forward to seeing if I notice a difference in how it performs.

The 32V'r tool is very nice compared to pulling the cam covers off and doing it the WSM way. In my opinion, it's worth using it to check the timing anytime that you're doing a timing belt job or have the cam covers off.

Thanks for the input on the correct timing for my non-stock cams.

FredR

Did you follow the guidance I offered to determine whether the error was due to adjustment or being one tooth out? If the adjustment screws are well off centre and close to range extreme chances are you may be a tooth out. Sounds as though you did not follow my advice to preset the cam sprocket at the centre of the adjustment range before fitting the belt. Either way, if you now have the timing correct how you arrived at it is somewhat academic as the object of the exercise is to get it correct.

If you can take a pic of where the screws are now on the sprocket that is giving you concern.

Bulvot

Fred,

I confirmed that the driver's side cam gear was one tooth off. I took a lot of careful measurements with the timing tool and compared them to the original belt position and vis-a-vis where the cams and timing should be. There is no doubt, the driver's cam was one tooth off.

In my last message, I said that the cam shaft bolt holes are NOT centered, and that was a typo. They are NOW almost perfectly centered in the slots.

Bulvot

From what I have observed, when the crank is at 45 degrees and the cam gear indicators are near the top of their rotation, the indicators are roughly three teeth away from the camshaft backing plate "V". That's how it's been in every photo that I've seen, and how it was on my passenger side cam. The driver's side cam gear was one tooth off from that position, and the cam shaft bolt holes were roughly centered in the cam gear slots. When I installed the new cam gears, with the slots centered over the bolt holes, and installed the belt with the drivers cam gear one tooth over from the old setup, I was only off by roughly a degree at that point. I don't do things half way or leave things "good enough". The cam gears are centered now, and the cam shafts are timed properly, so there is plenty of room for adjustment in the future.

Bulvot

One question that is probably unanswerable is whether the driver's side was off due to improper installation, or the belt slipping. I'm leaning toward the former, but the original tensioner was in really bad shape. It had leaked all of its oil out, and it practically fell apart as I removed it. But, the belt was tight before I backed off the tension on the tensioner, so....?

FredR

Excellent- well done- mission accomplished!

FredR

They are not "roughly" 3 teeth different they are exactly 3 teeth different when at 45 BTDC. The cam sprocket has 48 teeth so one revolution of the camshaft means the teeth are on 7.5 degree centers. Thus as the gearing ratio of 2:1 ech cam tooth represent 15 crank degrees x 3 = 45 degrees.

The belt has not slipped if the tension was correct- that being the case the reason was incorrect installation and that is not at all uncommon believe it or not. The tensioner oil does not impact that aspect. The Belleville washer pack acts both as a dynamic spring restraint and applies a correction for thermal expansion of the motor during warm up helping to maintain correct tension during this transient. That being said the tension alarm does not alarm for the first three minutes of operation to avoid false alarms. Although not everyone agrees, I concluded from studying the tensioner that it also acts as a damper- as to how well it does this remains to be seen. Porsche have patents out on this device- clearly they did not get the patent awarded for repeating what others had done before them. The belt determines how much tension is needed, how it gets the correct tension is somewhat irrelevant as long as it is adequate and reliable.

Bulvot

Everything is back together, and the car runs great. I took it for a drive and no issues presented themselves. With respect to power, there is no way that I could objectively compare the before and after. But, it definitely didn't feel down on power.