Generator tach drive gear

[Jeffrey C.]

I rebuilt my tach with one of the available Corvette Central kits and It runs aprox 1500 over the real RPM. Of course the entire dash is together so Its going to be fun to fix. Before I pull the dash can anyone tell me if the metal gear on the end is the same for 57 and 59? The catalogs list it as the same. I use a late 57 or early 58 generator on the car so if the gear is different that could be the cause. I suspect it is a defective rebuilt kit.

[Bill Clupper]

Re: Generator tach drive gear

same gear for both applications.

[John H.]

Re: Generator tach drive gear

Jeff -

C-1 tachometers are notoriously inaccurate, even when properly calibrated; they're better suited to indicating that the engine is running rather than indicating how rapidly the engine is turning over. I fabricated a hinged mount and keep a small (2") AutoMeter electronic tach clipped up under the dash on my '57 - when I really need to know accurate RPM, I just flip it down into view and it works fine. Of course, the AutoMeter tach doesn't tell you that your engine has turned over 16.487643987 gazillion times like the stock one does.....

John

[Doug Flaten]

Re: Generator tach drive gear

You probably need to investigate the generator and crankshaft pulley sizes. I'll have to defer to some other experts or at least someone with references for your year as far as the correct sizes.

[Jim Mitchell]

Re: Generator tach drive gear

Jeff,

I have a '60 and replaced the tach head with a rebuild/refurb unit from Dr. Rebuild. After replacement, I connected my trusty dwell/tach meter to my distributor and compared the readings. The '60 tach unit read quite a bit higher. I then took the tach assembly to a speedometer repair shop. They have calibrated equipment that allow the tach head to be slightly degaussed to correct the readings. After having this process performed, I rechecked the readings on the tach and the electronic dwell/tach and they were very close.

As was stated in a previous post, the pulleys must all be of the correct diameter or all this calibration work will be for naught.

Jim