968 Timing Belt

[ledhedsymbols]

So there I was.... Working on the 968, throwing tools and saying things I learned in the Navy and nowhere else.

I finished replacing the water-pump today, so it's time to get the rollers and belts squared away. There is only one problem.

When I route the timing belt, I start from the drive sprocket, past the wasserpump and tensioner applying all the tension I can on the long side (right side as you look at it) and up to the cam sprocket. As soon as I apply tension on the tensioner arm to unleash the hydraulic tensioner, the cam sprocket rotates 1/2 tooth counter clockwise.

A couple taps with a dowel and the sprocket is back where it belongs, but as soon as I try the process over again, it's same story.

I have to work all weekend, so I will not be able to get to it until next week at the earliest, but does anyone have any tips or tricks that have worked for them? I would imagine it's a similar setup to the other 16 valve models.....

Speak O wise 4Banger Porsche gurus......

Micah

[Techno Duck]

I think i understand what your saying. You are saying with the cam gear set to the TDC mark, you put the belt on and as you release the tensioner, the cam gear moves a tooth or so off?

This is a common problem with the 944 also, what i do to get around it is set the cam gear one tooth forwards (or however much the gear moves in your case) and put the belt on. As you release tension, the cam gear will move back, but will move back to the correct TDC position.

[ledhedsymbols]

You are correct in your understanding of the problem....

I have tried what you suggest, and I can only get it to TDC. I haven't been wailing the crap out of it... I have no desire to jack up the variocam system by handling it too roughly.

Any other thoughts?

[todd84944]

IF I follow you correctly, you are putting the belt tight around the tensioner and the water pump, and leaving it loose going from the cam sprocket to the crank sprocket. If this so, I put the slack on the tensioer, then release. If you don't have a flywheel lock, the crank will turn some when this done. I usually try pull the belt a little tight between the crank and the tensioner, then release the tenisoner.

[ledhedsymbols]

The flywheel is locked, and I am putting the slack on the tensioner. I have been pulling as tight as I can on the crank to cam sprocket run, and then applying pressure to the tension arm. I still can't seem to get that extra 1/2 tooth I need from the belt to square it all up.

[SolReaver]

Try unlocking the flywheel, as Todd says the crank might shift abit one way or the other. Don't feel bad about walking away and starting fresh a bit later. Just a tooth off can be frustrating. As long as it all lines up when you are done.

oh btw, I have never DONE a timing on a 968, just 944s so follow my advice at your own risk.

[bazar01]

Yep, with half a tooth off in the cam sprocket, try unlocking the flywheel lock and rotate the crankshaft until the "OT mark in the flywheel is lined up with the stationary pointer. You might be lined up after all. The flywheel lock will throw the flywheel TDC off a little whe installed which would explain the half tooth off in the cam sprocket.

[nynor]

1/2 tooth off? there is that much play in the belt when it is tensioned properly. don't believe me? get the belt on, remove the flywheel lock, then rotate the crank either direction. it will move at least 5 degrees on the flywheel before moving the cam.

[ledhedsymbols]

Thanks guys, I'll give it a whirl in a couple days when I am off work.

Damn shame I still don't live in West Jordan, I'd give you a holler Nynor.

Thanks Again,
Micah

[nynor]

that would be a good time! i've done the belts, start to finish about 3 times. adjusted tension about 8 times.