What is this?

[79ramp]

For my next potentially stupid question today: I have a '79 C30 with a 454 and it has this box which is wired into the distributor and has a 2-prong plug going to ???. I have a few questions on it:

1. What does it do?
2. Can I bypass it? Where can I find a wiring diagram for it?
3. If not, what does the 2-prong plug go to? I don't know that it was ever plugged in on my rig.

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[79ramp]

I knew it was a stupid question. Finally found a decent wiring diagram and I think this is what I am looking at. Looks like I can just connect the 3PNK-3 wire to the positive side (if you trace it all the way through, it goes to the ignition switch) and the 8WHT-121 to the tach side and cut out the rest.

I am assuming since the 8911288 plug has never been connected to anything, it has probably never done anything anyway.

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[CorvairGeek]

I wasn't sure of the purpose of the relay, but that is definitely a picture of a SBC, not a 454.

 

[Rusty Nail]

Ruh-rohhh!

 

[1987 GMC Jimmy]

I wasn't sure of the purpose of the relay, but that is definitely a picture of a SBC, not a 454.

Good eye!

 

[CorvairGeek]

The hood springs and cowl aren't '79 either, so it may take some sorting out.

 

[1987 GMC Jimmy]

The brake setup looks to me like something you’d see in a big block. It might have originally been a 454 truck and someone swapped in a 350.

 

[CorvairGeek]

Yes, hydroboost, 1 ton system. I was guessing an engine swap too, as the fan blade is so far out of the shroud, as a BBC fan shroud is too short for a little SBC.

 

[79ramp]

I probably should have clarified, the picture is not my truck, just an example I found on-line. I put new valve covers on mine so the stock mounting spot is gone (plus I was not at home so couldn't go get a picture).

 

[CorvairGeek]

I probably should have clarified, the picture is not my truck, just an example I found on-line. I put new valve covers on mine so the stock mounting spot is gone (plus I was not at home so couldn't go get a picture).

That's good! I was concerned you were in for some surprises.

 

[79ramp]

That's good! I was concerned you were in for some surprises.

Yeah, that would have been a bunch of big surprises

 

[Rusty Nail]

Good times...

 

[Craig 85]

GM lists it as an engine speed switch. I think it's related to the emissions system, but it could be part of the cruise control too.

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[crpntr78]

I don't believe it's cruise related. I have that same item bolted to my driver side valve cover and my truck is an 84 K2500 Sierra without any frills.

 

[DoubleDingo]

I probably should have clarified, the picture is not my truck, just an example I found on-line. I put new valve covers on mine so the stock mounting spot is gone (plus I was not at home so couldn't go get a picture).

I ran into the same thing when I swapped in the vortec heads and valve covers. I tried finding a pic of where I put it but can't seem to find one. I don't know what it is for though.