# Questions on factory engine compartment wires with updated engine



## 70conv (Jun 25, 2012)

Guys,

I'm getting ready to install my newly rebuilt 400 engine and I have lots of questions regarding all the factory wires for the stuff that was on the original(ish) engine. I've upgraded this build with a Holly carb, single wire internally regulated alternator, aftermarket gauges, and an MSD distributor. What this means is I no longer have or need (I think) the original temp switch, the TCS vac solenoid, the voltage regulator and alternator wiring harnesses, and the transmission switch that my wiring diagram is connected to the TCS solenoid. I am running the factory air cleaner unit with vacuum input from the carb but not sure if that vacuum is actually supposed to come from the TCS vac solenoid??? My questions are:

1) If I just junk the alternator and voltage reg harness and wire the alternator to the battery, how does the fuse box get power? 

2) What essential functions, if any, does the TCS solenoid perform? Can I live without it?

3) What function does the transmission wire harness perform? Can I live without it? 

4) Can I run the vacuum input for the air cleaner from a carb vacuum source or does it have to come from the TCS?

In addition to making sure everything works properly, I would love to be able to unclutter the engine bay a little by removing unnecessary wires so any harness that can be removed it would be great to know. Thanks so much for an assistance you can give on this!

Mike


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## GTO44 (Apr 11, 2016)

70conv said:


> 1) If I just junk the alternator and voltage reg harness and wire the alternator to the battery, how does the fuse box get power?
> 
> 2) What essential functions, if any, does the TCS solenoid perform? Can I live without it?
> 
> ...


1) yes, get rid of the alternator and voltage regulator. Get rid off the wires except for the heavy Black/Red coming off the factory alternator running to the firewall bulkhead connector. This is the wire that supplies main const 12v power to the ignition/fuse block. Use at least a 4awg wire for the new 1 wire from alternator to battery. Either hook that heavy black/red wire to the alternator post or directly to Batt+. And an fyi your gen light will no longer e functional but you probably knew that when buying the one wire setup.

2) The idle solenoid looks to be of the kind that when power is cut, completely closes the butterflies on the carb to prevent engine run. It can go.

3) The "trans wire" as you say should be the kick down switch. It's a black/yellow drawing power from the wiper connector and sending a black wire to the trans according to the diagram . It's what tells the trans to downshift when you kick it in the ass. Yes keep it.

4) I think you may be referring to the EGR solenoid, not a TCS solenoid. It's an emissions deal and I would just cap it unless you're going for the all original setup which I doubt since you put a holley and other stuff on it. There's no reason for a vacuum line from the carb to the air cleaner, it will just create a vacuum leak. I'm not super familiar with the setup off a '70 gto but typically (if your running a pcv system) one vacuum line off the pcv to the carb/manifold vac. Another vac line from the valve cover to the air cleaner to provide fresh air to crankcase. 

* Note when removing the voltage reg wires get rid of them all but be careful with the red wire in position #3 on the reg. It runs to a junction before the firewall where it meets with a heavy wire from the starter and a green wire that takes it to the bulk head. Remove the red volate reg wire from the junction but keep the green wire and wire from starter connected. This also feeds power to the ignition. 

Attached is the 2 pages of wiring diagram i referenced... It may not be exact but it will help you track where everything is going...


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