How would i go about installing a tachometer in my 86 cadillac eldorado? wht do i wire it up to, and how difficult is it to find these wires and how hard is it to reach and splice them. thanks in advance.

I have installed two tachometers in my short life, and both were in a Chevette. In both cases, you need to tap into a power source (switch), likely your dimmer control if you want the lighting on the tach to be controlled by the dimmer switch, a ground, and a wire to one wire coming off the distributor. Did the tach not come with instructions? If not, that should be a start. Hopefully there are four wires, otherwise I guess I have either included something I shouldn't, or excluded something. At least it is a vague start!

Is your car equipped with a HEI distributor? If so there's basically a port where a tach can be plugged in or so I've been told. Never checked myself. But basically all a tach takes is a signal from the distributor and a power wire, along with a setting to tell it how many cyls the engine has.