71 Tachometer Advice, Please

[Peter B.]

Hi Team,

Long time!

I need some advice. When I bought my 71, it had the tach cable disconnected. I think I tried connecting it once but did not work. Obviously, stripped gear. What do you recommend I do? I really do not want to remove the whole distributor to change the shaft unless I Really need to. Should I just replace the drive gear to see if that is the problem first? Any advice and any guidance on where I can find detailed instructions would be GREATLY appreciated.

Thanks

Peter

[Terry M.]

Re: 71 Tachometer Advice, Please

Peter,

If you find only the tach gear damaged -- go buy a lottery ticket or two or three. Almost always both the shaft and gear are toast, but there is always the chance the tachometer head is bad, or the cable is broken. If either of the latter is the case, you will wish it was just the distributor.

For the distributor:

http://www.tispecialty.com/articles/article6.htm

This web site by David Fiedler is a wealth of information. Bookmark it, and if you decide the distributor needs more help than you can give it Dave or Bill Clupper will be happy to help you out. Bill is available through the "Members List" on the blue bar above. Both are long-time members of NCRS and forgot more about distributors than most of us know.

[Jim M.]

Re: 71 Tachometer Advice, Please

It's not difficult to remove the brass coupling from the distributor to then remove and inspect the cross gear for wear. Usually it gets trashed because of lateral movement when the nylon button is gone from the distributor housing (it pops in from inside into the small hole on the opposite side of the housing). When you have the coupling and gear out, you may be able to see the condition of the gear on the mainshaft using a mirror and light. If it's badly worn, the only fix is a new mainshaft at which time I would also check for wear in the upper and lower mainshaft internal bushings. They are replaceable too. If you're lucky, the mainshaft might still be OK. The button and cross gear will not be hard to find. Good luck getting it working again. Regards, Jim

[Jim M.]

Re: 71 Tachometer Advice, Please

I totally agree with Terry. It would be helpful to try spinning the cable core by hand while you look at the tach to see if the pointer needle moves and that it turns freely.

[Robert S.]

Re: 71 Tachometer Advice, Please

Chuck the cable end in a battery operated electric drill. Put the drill on low speed and run it backwards and look to see if the tachometer needle is showing RPM. It probably will show RPM so you know the issue is with the distributor. Very likely the main shaft is damaged and if you keep running the distributor with the damaged main shaft the pieces of damaged gear teeth could wind up damaging the main shaft bearings. If the distributor is the cause of no RPM and if the distributor has never been serviced, it is probably a good to have it disassembled, have the main shaft, cross shaft and bearings inspected and replaced if necessary and the whole thing cleaned and relubricated.