#1  
Old 11-29-2021, 02:44 PM
Drdach Drdach is offline
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Default Does anyone know what this is

1970 Grand Prix SJ 455 HO motor....not sure what this component is. It has the electrical connector hooked up but nothing else. Any information appreciated...it sits next to the coil at the back of the engine
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  #2  
Old 11-29-2021, 03:28 PM
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Sirrotica Sirrotica is offline
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If my memory is correct, it's a vacuum control solenoid to control the vacuum advance for meeting smog regulations. I think it was for limiting in high gear if the distributor received full advance, near as I remember. It may have been controlled/limited by coolant temps. I'm trying to recall from 50 years ago, when I graduated from high school, and began my trade as a mechanic, so it's not right at the forefront of things I recall. It's location was on the rear of the intake manifold, close to the vacuum advance can on the distributor.

It was one of the first things that got bypassed if you wanted full advance all the time. I do remember that..... it usually was never removed from the engine, just taken out of the vacuum routing. Just like what you have shown.

If I remember correctly, there was a small foam rubber filter on one of the fittings that was exposed to atmospheric air, they deteriorated within a few years of under hood temperatures.

I hope that helps answer your question.

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  #3  
Old 11-30-2021, 09:45 PM
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428ho4spd 428ho4spd is offline
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Exactly what Sirrotica said above.
It's called a TCS solenoid (Transmission Controlled Spark) and it's controlled in two ways... by temperature to aid with cold starts to help warm up the engine and also at high temps to help cool it down by allowing full vacuum advance in both conditions. The transmission side of it is controlled by a switch on the trans which allows full advance when it shifts into 3rd gear at cruising speeds. Your solenoid is actually mounted incorrectly, the bracket mounts onto the passenger rear head near the heater hose fitting. Once installed correctly on the passenger side... the long nipple opposite of the electrical connector is left open, this is where the little foam filter would go as mentioned above. The plastic nipple pointing to the drivers side (where the cut off hose is attached now) goes to the vacuum advance unit and the metal nipple under the electrical connector goes to the vacuum fitting at the rear of the carb. If you want to get it hooked back up and working, I can help you with that.
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  #4  
Old 12-02-2021, 12:40 PM
Drdach Drdach is offline
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Thanks for the help and great explanations. Glad I found this Forum, learning as I go

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