Factory tach help please

[ozark]

Could someone please show me where on the firewall the wire that goes to the dist for a factory tach goes through the firewall on a 1978 era truck. I think it is near where the accelerator pedal bolts to the firewall but not real sure.

[motornut]

i would think it would be "in" the harness going to the engine
I added one to mine(harness),have yet to hook it up.
just a temp wire for now

[hatzie]

Originally Posted by motornut

i would think it would be "in" the harness going to the engine
I added one to mine(harness),have yet to hook it up.
just a temp wire for now

According to the wiring diagrams... the stock Tach wire goes through a grommet in the firewall all by it's lonesome.
Not sure where the stock location is though.

The heater wiring, 4 speed backup lights and, TH400 kickdown wires do this as well.

[motornut]

oh then the man to ask woud be Keith
actually his truck has one may spot it in his thread

http://67-72chevytrucks.com/vboard/s...342926&page=25

i know mine came with the right plug/harness,and it was seperate

[billybobjimmyjoejack]

I have a 78 that I ordered with the factory tach. It took me a while to trace the wire and this is what I found. Starting at the distributor the wire (brown) goes to a resistor on the firewall just left of center, then it goes into a split wire loom as it continues to travel to the left side of the truck. At the end of the loom it turns downward just below the backside of the fuse panel assembly and "yes" it does go through the firewall in it's own grommet by itself. From inside the cab you will see a bundle of wires just below the fuse panel and about 1 1/4" to the right of that bundle is where the wire comes through.

[ozark]

Thats it! Thanks for the pic billybobjimmyjoejack and everyone else. Now I have to figure out where the orange kickdown wire for a turbo 400 goes through the firewall.

[motornut]

hmm good to know,explains why the tach/brown insulation seemed so thick