A Problem with Tach "Bounce" on My 1971Porsche 911 -- Solved!

Hi folks --- out of the blue yesterday my Tach started to bounce -- a first just a bit at idle, then crazy no matter at what RPM. So I started by checking grounds -- and the one between transmission and body was a suspect because I moved it ever so gently when I re-did the rear calipers last week. I sincerely doubt that the ground underneath was the problem however. Since the Tach runs directly off the distributor the next thought was check all grounds around the distributor. And take off and put back on all major connectors, two of which are located in the engine compartment.

I then opened the distributor and found a rotor with a contact that was pretty much cruded up. I took a burnishing file, cleaned it up and ran the car for 45 minutes for so -- no more bounce! Of course, I ordered a new rotor from Rockauto -- probably should order two, one as a spare.

There is always something to do on my 1971 Porsche 911T!