help on 91 C2 distributor drive belt

Just bought 91 C2 and have heard of potential problems with breakage of drive belt for dual distributors. Any advise on how to check / replace this belt?

Pull the distributor caps and try to turn the rotors by hand. If one spins free, the belt is shot as the two are not tied together by the drive belt.
There's a retrofit kit available from Porsche that vents the distributor housing as the belt disintegration was supposedly caused by a build up of ozone from the electrical activity. The kit is a piece of hose, a coouple of nipples and about $10. Somewhere in these posts is a note about it with the part #. If I find my receipt, I'll add to this.
While you're in there, check and maybe clean all contacts in the caps 'cause the voltage is hard on these units. If a cap fails, the computer can misdiagnose and think it's a knock sensor. If in doubt about the caps,replace them, you'll notice the difference.

Originally posted by FRED/LI:
Pull the distributor caps and try to turn the rotors by hand. If one spins free, the belt is shot as the two are not tied together by the drive belt.
There's a retrofit kit available from Porsche that vents the distributor housing as the belt disintegration was supposedly caused by a build up of ozone from the electrical activity. The kit is a piece of hose, a coouple of nipples and about $10. Somewhere in these posts is a note about it with the part #. If I find my receipt, I'll add to this.
While you're in there, check and maybe clean all contacts in the caps 'cause the voltage is hard on these units. If a cap fails, the computer can misdiagnose and think it's a knock sensor. If in doubt about the caps,replace them, you'll notice the difference.

Any information on how to replace the belt if it is broken or worn?

Great post! didn't know about the computor misdiagnosing the dirty caps as a knock sensor, just had a series of these error codes recently, will surely check that asap! As to the drive belt, I've heard that it is not advisable to replace the belt only, as installing it can cause stretching, mostly I've been advised to exchange a distributor for a rebiult unit. I did a posting on the dist. vent kit about a month ago. If you do decide to replace just the belt let us know how it goes.

Thanks for the information. I will try to find your prior post on the venting. I don't know if the drive belt needs to be replaced yet, but will probably try when it is needed.

Vent kit is in the Pelican listing of parts for the late model cars. It's a simple process once you figure where to drill the air housing and manage to do it on a flat surface so the drill won't wander and offcenter and oval the hole being drilled.
You'll see what I mean. Have fun.

Checked the drive belt yeaterday, it was fairly easy. After aligning the timing mark on the Z1 mark, with rotor pointing at the #1 plug wire, I removed the dual distributors. The drive belt can be seen and inspected by looking down inside the top of the #2 distributor while turning the drive shaft. Any missing teeth or cracks can be seen. It looks like removing the belt would require complete disassembly of the distributor, which was not needed. I will get the vent kit and go through the process again to install it!