1983 Chevy C20 Suburban 454 wiring

[ColAdo82K5]

Hey squarebody fans,
Two questions:
1. My 454 HEI distributor has a factory wire running to the TACH spot on the cap...but this is not a truck with a tach...what is this for? AND I want to add a tach...is there a great place to splice into this?

2. On the drivers side valve cover, there is a electronic thingy bolted down...factory wiring harness...is this part of the cruise control or the turbo 400 down shifting?

Thanks in advance!

 

[wasted wages]

Are there two wires at the cap? If so,
one will be power to the distributor...and one will be the wire to the tach.

If there is only one " factory" wire then it has to be the power wire.

It's hard to see sometimes but there are two terminals at the cap that plug in.
One marked Bat.
The other marked Tach.
That terminal can be used to wire to a new tach.

As far as the "thingy" on the valve cover...a picture would help. Others may know more...

 

[diesel4me]

The TH400 downshift switch is located up under the dash above the gas pedal on square body trucks..the gas pedal activates it..

Not sure about the thing on the valve cover--some years (mostly 70's) did have a "transmission controlled spark solenoid" that blocks vacuum to the distributor advance in high gear to reduce emissions...

 

[ColAdo82K5]

For the HEI, there are two wires. Both factory. The power wire and the tach wire.

For the electronic thing on the valve cover...83 was the first year of not using the speedo cable for cruise control...so I think this box is for that. My speedo cable is a one piece. It doesn’t use vacuum lines or anything for this electronic thing in question.
The downshift cable is there for the 400. The orange wire is there for the 400.