Distributor Wiring Harness connections

Hopefully someone can give me an idea on this.

I have a 74 TA that needed a new distributor over a year ago.  I purchased an Summit HEI blueprint Distributor.  right after it came to the house I had to go to the Middle East and have been here for a year.  A friend of mine descided to surprise me and changed out the Points Distributor for the HEI.  He then also changed out the engine wiring harness.

The car runs great now but without a tach.  The Tach worked before the HEI and wiring harness was installed.  The distributor is missing the wiring harness from the Distributor to "whereever" it used to go to send a signal to the tach.  I dont know if the wiring harness went to a connection on the firewall or to a connection on the wiring harness.  the wiring harness he ordered and installed is for a HEI car, but my car originally came with a points distributor.

Can anyone enlighten me on where in the engine compartment the Distributor wiring harness plugs into the car besides the plug on the Distributor?  

I'm a Grand prix lovin bodyman but I'll give it a shot because I think I understand the question.

First, pop the coil cover off the new HEI. If the coil says china on top, throw it as far as you can and go get a Borg Warner or other decent one. Mine crapped, just sayin! I wouldn't trust the module much farther than I can throw it either.

Unfortunately I'm looking at a crummy wiring diagram but it appears that the old ignition wires passed thru the firewall in the same connector as the wiper motor, temp and oil sensors, and the old purple coil wire / fusible link plus the yellow to the starter if that helps. I do not know if the tach signal input on your car is part of the printed circuit or a seperate connector, probably seperate originally. Look at the back of the tach?

One of the Firebird guys would have to confirm that its OK to hook the HEI to the factory '74 dash tach, but I think its OK.

I would run my own new wires for both HEI power and tach feed. You could even pass them thru empty spaces in the old connector without cutting the new wire, possibly. I like to pick up HEI power at the fusebox and go straight to it without a firewall connector.  

74 had a points Distributor still?
Thats odd... I thought if memory serves that the HEI was incorporated...
Anyhow.. the wire that ran your tach attaches to the middle pin where the wires connect to feed power/ground to the distributor.
Like I.D.J said above Run your own new wires 12/14 gauge for power, and a 14 or 16 for gauge for the tach.
And hooking the factory tach is no different than aftermarket one.. Just be sure you have the correct wire...
Do yourself a favor.. lesson I learned afterwards.. take white electrical tape and label wires under the dash! cant be seen and saves you tracing whats what over time and changes you make. If you got a label maker.. use it.
Simplify it for yourself.
Now that you mentioned that I.D.J.... I need  to disconnect my Column tach and see if that is causing my issue with hood tach or if my hood tach needs to be recalibrated.. it did work.. but not as of late.
Great post.. got me thinking..  
Viagra and Torque are one in the same they both get you up!

Iron- 73 was when we got retractable 3-point inertia seat belts. 74 was 5MPH bumpers. 75 is when GM went across the board with HEI and catalytic converters in most of the U.S. The year of the dreaded "unleaded fuel only" decal. Some vehicles did have the option of transistorized ignition earlier than that, such as Corvette.

If not running an aftermarket ignition "box", the tach signal wire can go directly from dist to tach.  

+1
Gotcha... I never left points in my cars for very long...
Something about it being antique and inadequate.
I dont get why some of these concourse cars leave them in when you can swap the guts out and no one would ever know.LOL  
Viagra and Torque are one in the same they both get you up!

The manufacturer of the wiring harness told me to look for a brown wire coming from the firewall and that is to the tach if it is all orginal.  So will let you know what I find out in a couple of days when I get home, pending the sand storm here in the middle east.  Flying home tomorrow night.  hopefully the sand will let up  

You were 100% right on the distributor.  I was at home about a month ago and took the ole girl out for a little spin.  I noticed under hard acceleration she would miss a little at the higher rpms and when I let off the gas it would quit missing.  

Yep, made in China on it.  Just bought a Mallory 75 series HEI and putting it in on this cam change.

Thanks guys for your help.  Most of the time, buying cheaper stuff is more expensive  

So when you need something sandblasted you just set it outside overnight? Just kidding, I was coaching a dude from Egypt once on a paint job and the sky looked pink in his pics, from the sand. I can't imagine painting over there in the desert areas. Glad you found that cheapo coil, now you have a spare that runs. The Mallory unit should be real nice. Good luck and stick with it!  

The factory Tachometer wire that runs through the firewall to the Distributor is a brown wire.  Got my Tach working  

The factory Tachometer wire that runs through the firewall to the Distributor is a brown wire.  Got my Tach working