My tach is off.

I had changed the alternator and belt at the same time when the alternator froze and chewed the belt up. I had slipping in the belt so it was too big. I had to put on a belt that was obviously a little too tight at the time. I later replaced the belt. The alternator went out again and I changed it. I recently changed the belt again and it is supposed to be the right belt, if there is such a thing. Everyone seems to think it's supposed to be a different size for some reason. It seems to fit right.

My tach is at 4000 Max speed in third. It should be around 3450 or 3500 from what I remember when it was new.

Is there something I can do to the alternator or is it just the wrong one. I don't think it's the pully.

Why is it hard to get the right belt? Anybody else had this problem?

Thanks Edited by: DavidPhillips

You got a pulley from a gasser. If you can access the old one it would be best to swap, otherwise a guy will need more info.





IIRC, the common sizes were 56mm, and 62mm...

Your probably right, I didn't really look at it close enough I guess. It wouldn't take much to throw it way off.

The tach reading comes from the alternator, consequently an incorrectly sized pulley on the alternator will vary what the engine is actually turning. Always thought that this was an odd place to get a reading for engine rpm.

It only changes the tach reading. Not the engine speed or top speed, shifting or anything else.

Nice to hear that I wasn't the only one who has made the same mistake to put too short belt and ruin the bearings of alternator. It seems to be very important that you place right kind of belt...

Actually the first alternator burned out the rear bearing with the original belt on it. They get hot and go out according to what I have heard.

The belt that I got from a parts house was to tight, because the tensioner/brake was not in the original position. I thought it was affecting the tach, and it probably was. When I got the right belt the tach was still off.

My second alternator just stopped working. The belt that I got with the alternator was too loose.

Where I went wrong I guess was when I changed the first alternator I did not check the pulley. The second one was the same size as the first, so I guess they were both the wrong size.

If this one goes out I'll get the right pulley on the new one.