does anybody know if the six cyl and 8 cyl tachs are interchangable I am removing a 300-6 and installing a 460 and Im wondering about tach(factory installed) compatability? The truck is an 88 F250 oridinally fuel injected now going to be carberated. Thanks chris

 

Well, if you ever figure out the right wires, and if the tach has a 4/6/8 cylinder switch on the back, you should be ok.

Your getting rid of the original ignition system I presume, since it needs the computer to work. So you will have to find where the tach got it's signal from in the efi harness, and take this wire and put it in the right place on whatever ignition you are going to use.

If there is no selector switch on the back of the tach for 8 cylinders, it's not going to work right. It needs to know there are now 8 pulses per rev instead of the 6 pulses per rev it had with the old motor.

 

finding the wire in the harness should be no problem i am just trying to determin if the factory tach has a 6/8 selector or what changes may be necessary without removing the dash just yet.
Thanks chris