rob76turbo

Replaced the belts, rollers, waterpump and a few other items on my '86 951. But after tightening the belts, I noted that the timing belt seem to slide back on the teeth of the cam sprocket and on the last couple of teeth, the belt pulls away from the surface of the teeth.

I do not have the 9201 tool so it the the twist method as far as checking tightness. I set the tightness at a 90 degree twist. Any thoughts if I have it too loose or too tight? I seemed so run roughly when I tightened it a bit more, but still the belt works its way back off the front of the sprocket.

I will post pix later tonight when I have the cover back off.

Black51

When you tighten the belt, the flywheel moves a few degrees. So you have to counter that by rotating it back a bit before you tighten it. That way, it will line up after you tighten it. The cam sprocket moves a bit sometimes too.

rob76turbo

Is it best to have the fly wheel lock or have the car in gear to keep the flywheel / cam gear from moving?

Tom M'Guinn

I don't generally use a flywheel lock when I put the belt on. Just watch if the cam wants to turn, and compensate when you put the belt back on. Most importantly, once the belt is on and tensioned, triple check to make sure the cam and crank TDC marks are aligned. Check the marks immediately after installing the belt, check them again after tensioning the belt, and check them one last time after the car is all back together.

The tightness of the belt (within reason) should not affect if the engine runs rough or smooth really. I'd check the alignment marks and see if they are aligned. Very hard to say if 90 degree twist is too tight or loose -- sounds loose to me but I suppose it depends how hard and where you're twisting. There are several aftermarket belt tensioners you might look into if you can't get your hands on the factory version, such as:

http://www.arnnworx.com/catalog/inde...527090c0e4caea

http://www.rennbay.com/belttutorial.html