I recently blew the motor in my 86 firebird (2.8l). I did a 3.1 conversion due to no yard having a 2.8 in my area. Everything is running fine. I had to switch over a little bit of wiring (2.8 clips were different than 3.1 --spliced the old wiring onto the the right clips) Everything is running fine, except the tach does not work (its an auto). I was wondering where on the 3.1l (or what sensor) actually picks up the engine RPMs? I looked all around, and couldnt find anything. If someone knows where the sensor or wiring is located, or where to look, ill be greatly appreciative. Thanks in advance guys

 

You have to get a tack from a 3.1 liter car, you can't use a 4 cylinder tack on a 6 cylinder engine.

 

well i have a 87 ta with the carbed 305. about 2 weeks ago my oil sending unit went out. it was right there beside the distirbuter. for me there is a wire on the bottom of the dist. that goes to the tach. i know this because my jack legged friend that took the old oil sending unit off unplugged the TACH wire. so i go to start it and oil psi is up there with no tach. so i had to get back under there and plug it in... but i dont know if that is the same with the V6...

 

If the 3.1L has a single ignition coil, connect the tach lead to the negative side of the coil.