"62" tach

[Carl R.]

I have a 62 vette and the tach needle wants to jump all around when I am holding a steady engine speed. I have replaced the distributor shaft and cross shaft gear, and greased the cable going to the tach. The ends of the tach cable show a small amount of wear but does not slip in the coupling on either end. Does the tach gage need to be replaced or rebuilt or is this a common thing with this type of tach drive in these cars.

[Paul D.]

Re: "62" tach

Something worth checking before pulling out the tach is distributor orientation and how much of a bind the cable is in. Does the cable bend severely before it attaches to the distributor? Lots of threads on this board address distributor orientation and I know it is critical on my C3. Usually, a misplaced distributor will result in manifold interference before correct timing can be achieved but will also cause cable bind. You may want to look under the dash and make sure the cable is not misrouted causing a bind. Chip.

[Joe L.]

Re: "62" tach

I have a 62 vette and the tach needle wants to jump all around when I am holding a steady engine speed. I have replaced the distributor shaft and cross shaft gear, and greased the cable going to the tach. The ends of the tach cable show a small amount of wear but does not slip in the coupling on either end. Does the tach gage need to be replaced or rebuilt or is this a common thing with this type of tach drive in these cars.

Carl------


Corvette tachs through 1974 are not direct drive units. They incorporate a "magnetic drive". In time, things go "haywire" and produce just the sort of mis-operation you are experiencing.

[Joe R.]

Re: "62" tach

The word "greased" should never be used in the same sentence with "Speedometer Cable" or "Tachometer Cable". Lightly Lubricated are the words you should use in conjunction with those two words. Some Corvette suppliers sell "Cable Ease". Using Cable Ease correctly will insure that you don't have problems with the speedometer or tachometer! Using either "Grease" or any other lubricant in EXCESS will insure failure of the speedometer or tachometer.
There have been many threads on the lubrication of these cables.
Not saying that is your problem but will surely lead to the problems you are having.

JR

[Ken A.]

Re: "62" tach

Joe, you sure he doesn't need the grease fitting attachment for the cable?

[Carl R.]

Re: "62" tach

I have already moved the distributor over one tooth on the cam gear to help straighten out the cable before it went into the fire wall. I saw that problem early on when I was trying to time the engine. Now I have seen that the cable under the dash has a half moon or a lazy S shape to it. This could be the problem, but I have not done any thing about that as of this time. The car is an original survivor that I have had just over a year, so I am trying to keep things as stock as I can. Now with that said, I am thinking that this is the way the cable is suppose to be, but if I need to put in a shorter one to get rid of that S curve in the cable I will do so. I will check into this as a possible fix. Now the lube job that I did on the cable, I just wiped some grease on it very lightly on the whole length of the cable. Thanks to all the people that responded to this thread, any information that I can gather on this matter would be great.