1971 TACH QUESTION???

[MRANT212]

Hope I can get some ideas as to where to start with this. My 71 BB coupe has an issue with the tachometer. Just started today when I decided to use it and drive @ 100 miles or so. The tach doesnt rev properly when the engine is reved. I was driving at 60 - 65 and the tach was reading a 1000 RPM's. At idle it barely registers 2-400RPM and I know its idling properly. Car is stock 454 4 speed. I know the tach drive is somewhere by the distributor. Any ideas you guys have would be greatly appreciated. I didnt even open the hood tonight to even poke around yet.

Anthony

 

[Vettehead Mikey]

It's pretty simple. It's one of three things:

-drive gears in the distributor
-drive cable
-instrument in the dash

Try the cable first.

 

[GTR1999]

Disconnect the cable at the dist and hook a cordless drill to it to see if the tahc will spin under power. If it appears to be ok then the cable and head are good and the problem is in the dist- most likely the main shaft and cross gears are stripped. The best replacement gears are from HyTech in FL. There is another one the catalogs sell that has a brass button on the head and are black. These were very poor quality a couple of years ago when I was rebuilding 2-3 distributors. They didn't mesh correctly with the main shafts and the replacment main shafts were just as bad. Check them carefully if you rebuild them, they shoud spin free by hand, any binding and you'll rip them apart when you fire the engine. Look at the back of the bore in the dist too for wear. The early ones are just cast iron and the cross gear eats into it. If this is the case you'll need to bore the hole and install a brass plug. The later ones use a nylon plug that can be replaced.

 

[MRANT212]

Thanks guys for the info.....Looks like I will be playing around with this when I get a chance. Iwill start with the easy stuff first!!

Anthony