C3 corvette tachometer problems
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C3 corvette tachometer problems
69 427 coupe. I’ve been trying to diagnose a bouncy tach needle. I believe it is the cable. It works fine at idle and low rpms but on acceleration it jumps wildly. I believe the cable is getting wound up.
I tried lubricating the cable with cable ease. That did not work. Is there a better lubricant to use?
I am thinking to try another cable. The one I have is a couple inches long. 19” is what I need.
am I missing something?
I tried lubricating the cable with cable ease. That did not work. Is there a better lubricant to use?
I am thinking to try another cable. The one I have is a couple inches long. 19” is what I need.
am I missing something?
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A check for the stock cable is to disconnect the cable from the distributor, chuck the cable in a portable drill to see if the needle still bounces (I don't recall which direction the drill is supposed to turn). If no bounce, I'd check the distributor drive gear. The brass fitting unscrews from the housing to reveal the tach drive gear. These are prone to failure but parts are relatively inexpensive.
Last edited by barkingrats; Aug 16, 2020 at 07:55 PM.
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How is your current cable only a couple inches long?
A check for the stock cable is to disconnect the cable from the distributor, chuck the cable in a portable drill to see if the needle still bounces (I don't recall which direction the drill is supposed to turn). If no bounce, I'd check the distributor drive gear. The brass fitting unscrews from the housing to reveal the tach drive gear. These are prone to failure but parts are relatively inexpensive.
A check for the stock cable is to disconnect the cable from the distributor, chuck the cable in a portable drill to see if the needle still bounces (I don't recall which direction the drill is supposed to turn). If no bounce, I'd check the distributor drive gear. The brass fitting unscrews from the housing to reveal the tach drive gear. These are prone to failure but parts are relatively inexpensive.
I will try the drill test and see what happens. Is there a better lube to use? What about lithium grease?
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,008
Likes: 4,166
From: US-PNW
the reason I believe it is the cable is it was working fine prior to replacing the cable. I changed it because the other one looked old and I had my dash removed and decided to change it while it was apart. Big mistake I guess. I have already changed the gear set in the distributor. I also added a 90 degree joint to eliminate the sharp turn from the distributor.
I will try the drill test and see what happens. Is there a better lube to use? What about lithium grease?
I will try the drill test and see what happens. Is there a better lube to use? What about lithium grease?
I'd not use lithium as I don't think it will be fluid enough in low temperature seasons. The lube I've seen and used is a rather liquidy reddish color. You don't want to use too much because the lube can work its way along the cable to the tach/speedo head and contaminate the works.
When you installed the new lubed cable, did it work fine for a short while and then start bouncing? If so, the lube may have gotten in the head.
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If you have the distributor positioned in the block the way the factory installed it, a 90° adapter shouldn't be necessary. GM changed the position such that the vacuum canister points almost directly to the left side of the car. The only alteration needed is to pull the spark plug wires and reinsert them one terminal position counterclockwise.
I'd not use lithium as I don't think it will be fluid enough in low temperature seasons. The lube I've seen and used is a rather liquidy reddish color. You don't want to use too much because the lube can work its way along the cable to the tach/speedo head and contaminate the works.
When you installed the new lubed cable, did it work fine for a short while and then start bouncing? If so, the lube may have gotten in the head.
I'd not use lithium as I don't think it will be fluid enough in low temperature seasons. The lube I've seen and used is a rather liquidy reddish color. You don't want to use too much because the lube can work its way along the cable to the tach/speedo head and contaminate the works.
When you installed the new lubed cable, did it work fine for a short while and then start bouncing? If so, the lube may have gotten in the head.
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,008
Likes: 4,166
From: US-PNW
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