when cruising in 4th gear at about 45 mph my tach shows im pushing 3500 -4000 rpms. the car has a 3.23 rear as far as i know. the car also shows it idles at 1500 rpm. whats the deal? is there a device i can hook up to my distributor and see what my actual rpms are?

 

Yes there is such a device. It's called a "tachometer". Any tune-up shop should have an engine analyzer, which also includes the tach function.

The tachs in these cars are notoriously inaccurate. As far as the factory is concerned, it's a trim package, not an instrument; so they think that as long as it goes up and down when the buyer mashes the gas, that's good enough.

You may also have a 6-cyl tach, which is calibrated (I use the word loosely in regards to factory tachs) to read one revolution for every 3 pulses; a V8 however will supply it with 4 pulses per revolution, which will make it read 33% too high.

 

Would an aftermarket tach solve the calibration problem? Or would it need recalibration, too?
Which is cheaper, recalibrating the stock tach, or buying a new $90 tach?

 

Hard to say... you might want to look around at junkyards for cars with tachs and snarf the little circuit board off the back of them. Probably they don't have to come out of one of these cars, I'd bet any GM car of the right age would have the same little circuit. There's a laser-trimmed resistor on them that adjusts them, I suppose you could cut it off and put a pot there and set it to where it's right and then get a resistor and solder it there, although I've never done that to one of these particular ones. One of the speedo repair shops might be a good place to ask too.