[Slick]

The original hood scoop wiring and vacuum controls were mucked up by a previous owner. I'd like to restore the "hood air valve" to proper operation.

Read Rocky Rotella's article about shaker scoops in Hot Rod, online. So, if I understand correctly, the vacuum controlled relay inside the scoop is fed 12V through a passenger side cylinder head located thermostatically controlled switch. That relay, in the scoop, is fed manifold vacuum so that the air valve only operates when the engine is over 140 degrees and manifold vacuum is at a minimum. The relay feeds 12V to the air valve solenoid when the engine is warm and throttle is depressed. Makes sense.

The air valve solenoid, vacuum switch and scoop mounted bulkhead connector are in place, in my car. But that's where I lose it.

Looked in my 74 Service Manual and saw vague references to the "hood air valve", but not much else. The thermostat is allegedly fed from a point "A" with a yellow wire. The other side of the thermostat goes to the scoop vacuum controlled relay via another yellow wire, along with a ground, to the 2-pin "T" form connector.

I can't find point "A", the thermostat or yellow wires on my car. Some previous owner made a crappy little harness from two 1/4" quick-connect flat blade connectors and a couple of pieces of #14 AWG.

So my questions are thus:

• Where is the 140 degree thermostat located? Exhaust side, or rear of the head?
  • Where is the source of 12 volts, point "A" (where lots of under hood engine wires connect)? It's not at the alternator, but I suppose it could be a soldered connection inside of the engine wiring harness.
• Does the switch actually have two yellow wires connected to it? The thermostat on the back of my passenger head has two different colored wires, neither of which is yellow.
• Has anyone experimented using an oil pressure controlled switch on the negative side of therelay wiring circuit? It would be necessary to find a normally open pressure switch to fit 1/4" or 1/8" pipe threads in the engine (at the distributor). The typical oil light switch is normally closed; i. e. closes contacts on pressure drop. I'd like that better than the thermostatically controlled switch.
  • Is the scoop bulkhead connector available anywhere?

Thanks!

Stuart

[SD455DJ]

Slick - Does this help any?

Dennis

[SD455DJ]

...helps if I add the picture...geesh!

[Slick]

SD455DJ,

Thanks, that identifies the source as the radio fuse. But where is the thermal switch located? I see a sensor of some sort on the rear of the passenger side head, it has two wires, but none are yellow. It otherwise seems to fit the bill....

Stuart

[SD455DJ]

Stuart - I'll try to get over to take a few pictures of my 74 (hope it was done correctly) and post them for you. It may take me a few days to get a chance to get over to where the car is to do that, if you can wait.

Dennis

[Slick]

Originally Posted by SD455DJ

Stuart - I'll try to get over to take a few pictures of my 74 (hope it was done correctly) and post them for you. It may take me a few days to get a chance to get over to where the car is to do that, if you can wait.

Dennis

Thank you Dennis, that would be great. I won't be able to get back to my car until Saturday anyway.

Stuart

[Red74Goat]

What are the first six digits of your VIN #? From 1st thru 5th digiit, should be 2 for Pontiac, Y or Z for base or custom Ventura, 17 or 27 for hatchback or coupe, B for 350 cu 200hp engine, 4 for 1974. Ex. 2Z17B4???????.

I have had a 1974 GTO in my possession since it was born in 1973 and my VIN is 2Z17B4....... I know the K for the 5th position is listed as the 350ci 4bbl, dual exhaust for 1974 Pontiacs, but I haven't seen a 1974 GTO VIN that doesn't have the B engine code in the 5th position, but maybe there were some produced with a K in the 5th position of the VIN..

Hope this helps with deciphering if it is a '74 GTO.

[Held for Ransom]

So, that's going to work with the automatic tube and dipstick?

[Slick]

It should. They're supposed to be on either stick or auto cars. Plan to check mine tomorrow. I'll let you know. If the dipstick is an issue, no reason not to fit it to the rear of the driver's side head.

[Held for Ransom]

Just revisiting. I was at one of the storage areas today and snapped a picture or three of the 350/manual 3 speed head and wiring. Showing position and matching AC 140M with 2713 date code.

[Slick]

The emissions sensor is on my car, but the scoop thermal switch is missing.

Any idea where I can find one?

I'm starting to wonder about my car. Missing that control and I think the harness. My door panels say Ventura, not GTO, I know someone put it together, but starting to wonder if it really is a GTO.

[SD455DJ]

Stuart, It's possible it was converted to a GTO...fairly easy to do. You should order the PHS, that would tell you for sure. I wonder if there was a separate GTO-only under hood wiring harness from the Ventura II.

Dennis

[Slick]

Originally Posted by SD455DJ

Stuart, It's possible it was converted to a GTO...fairly easy to do. You should order the PHS, that would tell you for sure. I wonder if there was a separate GTO-only under hood wiring harness from the Ventura II.

Dennis

Dennis,

PHS is on my to do list.

That thermal control switch is used in lots of GM applications. Gotta check my stock, probably have a few. Used to throw those things away. Now some guys are asking crazy money for them.

I can just use my TCS feed switch, it's the same, and I'm eliminating EGR and the vacuum advance controls from my car, so I won't need it.

Stuart

[Held for Ransom]

Originally Posted by Slick

Any idea where I can find one?

https://www.ebay.com/itm/11318149134...m=113181491342

[Slick]

Okay, just read the VIN code from a document that I have.

Mine is a fake!

M engine code, 350 2 barrel single exhaust.

Oh well, less of a concern as the 511, etc. goes in it.

Also, forget about maintaining the column shift because it was unusual!

A/C will stay, but no worries about altering a survivor.

Was so excited about getting the car, never checked the VIN before shipping it.

Lesson learned!

Stuart