I installed a complete speedo unit including the chrome trim in my car because it was in better condition than the original. It works but reads about 30 mph faster than I am actually moving. I can put the original head unit in and see what it does. What would cause the speedo to read so fast?

 

After so many years the magnets in them get weak and they'll do all sorts of crazy things. A good speedometer shop should be able to remagnetize it and calibrate it. Finding one who knows anything about the rollover speedometer may get interesting, though they all work the same way. The cable drives a magnet inside a cage and induces movement in the cage. The cage is what drives the pointer or in your case, speedometer drum.

One other thing to consider is tire diameter. If you're running a considerably smaller diameter tire than they came with (and I imagine that like most you have 215/75R14 on it, which are too small for those cars, I don't care what the tire makers' chart says) it can throw speedometer calibration way off.

Does your car drive it off the left front wheel or off the transmission? If it's transmission-driven, you possibly have a speedometer from a car with higher gearing than the 3.42 Starfires had, which will also throw calibration off.

 

tpawlik,If you can't get a correction through the speedometer head or new plastic gears from speedo transmission junction there is a apparatus that can be bolted to the side of the transmission housing that will correct this problem. Had this done on my 55 Olds when I mounted 60 series tires on it, cost about $150.00 a few years ago....Tedd