Just bought an after market tach to run in my 85 firebird 305 4 bbl. I have the 2 gauge cluster and a tach wire (a white wire) is already hooked up to the distributor. From the searching i have done on here and google i would just have to splice into the white wire for the tach signal. I cannot trace where the white wire ENDS but i can see where it comes into the firewall under the drivers side dash. Can i just splice into the white wire right at the firewall?? Sorry for silly question but i really dont want to mess with my electrical system. I have pics and a video to refer you to which white wire i am talking about. Thanks

http://i1373.photobucket.com/albums/...pse7922224.jpg

http://vid1373.photobucket.com/album...psd35e0790.mp4

 

I have the red hooked up to stereo power and black to stereo ground and the illumination wire with the stereo, seems to work fine. Just want to be sure about the tach wire before i go cutting wires. thanks

 

Doing my best to remember, but the white wire on my 87 305 carb was from the dist. This is the signal wire. If you pull your gauge cluster out, you will find it in one of the two connectors to your gauges.
Depending on where you are putting the tach, if you want your stock tach to work, you can either cut that wire and wire it to the signal in your new tach or you can splice off of it to run both your stock and aftermarket tach.
Which one did you buy? As some need a different input signal (4 cyl, 8 cyl etc).
That I don't know too much about since I only know enough to wire in an aftermarket (speedhut) tach to my ls1 computer.

 

i dont have a stock tach, just a 2 gauge (speed and fuel). i took the gauges out and all i had was a black and red wire which im guessing is for the fuel gauge as the speed is mechanical, no white wire. Just want to be sure im splicing into the correct white wire inside the car?? i would like to limit mess under the hood by not fishing it through the firewall. I bought a tach that is adjustable from 4,6 or 8 cyl. from princess auto (power fist brand). seems nice, got the light working and the power and ground wired. I know this should be easy but im an electrical dope!! I can rebuild a motor pretty darn good though

 

Princess auto eh? Where are you located? I'm in petawawa, almost 2 hours from Ottawa.

I can remember exactly what pin # it was on my car, but it is a white wire coming off the dist. And as far as I remember, it's the only solid white wire in that harness. That is the dist signal wire for the tach.

If you go in to the lsx swap forum, look at the "additional wiring" or info thread, there will be a post from Pocket that has the c100 pinout for your year of car.

The 12v supply to the gauges is pink with a black stripe, dimmer/light wires are grey (2 of those) and there are 2 black groin wires.
There is a brown wire in there that is for oil press, water temp I think was a green wire, fuel level was a pink wire I believe. Signal indicators were light blue and dark blue, high beam was a green, the brake light warning was light brown with a white stripe. That's off the top of my head.