Tachometer Cable Replacement
The tachometer in the Corvette has always been a bit 'bouncy'. Sometimes the needle is stable, other times it bounces wildly. I suspected the cable might be binding, so in 2020 I purchased a new one from Zip Corvette.
I'd put off installing it because I suspected it was going to be a difficult job, the type that makes you swear a lot. In theory it should be easy, just unscrew both ends of the old cable, remove it and replace with a new one. In reality it's much harder, there's very little space behind the dash so you need to be a contortionist to pull it off (unless you want to pull the dash out!).
Removing the shielding over the distributor is essential, you won't be able to access the distributor end of the cable or the hole where it passes though the firewall with this in place. With that removed, unscrewing the distributor end is pretty easy.
The firewall grommet on the '65 Corvette has 2 holes, one for the speedo cable and one for the tacho. It's easiest to remove and install this grommet from the engine bay side. You'll need to cut slits in the grommet to insert the cable, trying to get the cable ends through the holes is more trouble than it's worth (I detail this here).
Undoing the cable from the gauge is relatively easy, you just need to reach up behind the dash. It is possible to do this blind (sitting in the driver's seat and reaching under the dash), but you may need to get on your back under the dash and reach up next to the steering column. Attaching the new cable was much trickier, it's hard to get the thread started. I found it easier to do this using the 'reach behind' method.
Obviously this would all be easier if you dropped the steering column and removed the dash, but that's a lot of work, and you run the risk of breaking some of the very brittle, 60-year-old wiring behind the dash. I can attest that it's possible to install the cable without removing anything, in fact this is one of the few jobs on the car that requires no tools at all (just patience).
So, after 5 years of procrastination the tachometer cable has been replaced! Let's see if the needle still bounces.
I took the Corvette out today and, lo and behold, the tachometer needle is now solid as a rock. After years of putting up with the bouncing needle, replacing the cable was all that was needed. It's particularly nice at higher rpm, before it was hard to tell if you were at 4000 or 6000 rpm!
The larger knurled sleeve nut (left) goes to the distributor, the smaller one (right) goes to the gauge.
The larger knurled sleeve nut (left) goes to the distributor, the smaller one (right) goes to the gauge.
