Whats this?
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Posting Guru
Joined: Dec 2009
Posts: 2,134
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From: Mississippi
Whats this?
Hey, does anyone know just what this doohickey I'm pointing at is? As you might can see its mounted on the right hand valve cover. Got a vacuum line running from it to a "T" then to the air bypass valve. Engine is a '76 360, thanks.
MSEE
Joined: Apr 2004
Posts: 10,386
Likes: 35
From: Austin, TX
Exhaust gas recirculation (EGR) is a system that started in the early 70s to pull exhaust gas back into the combustion stream. The idea is that by the time the exhaust is brought back up into the intake, it is cooled down enough to cool down the combustion mix inside the combustion chamber (each cylinder). Ideally the exhaust gas is inert, so it doesn't affect the combustion chemistry by leaning out the mixture. This reduces emissions.
The EGR system always consists of an EGR spacer plate between the intake and carburetor, and an EGR valve on the plate to open and close exhaust flow into the combustion stream. The valve is vacuum operated. Most commonly the valve is controlled by ported vacuum through a temperature-controlled ported vacuum switch, such that the valve only opens during part throttle at full engine operating temperature.
In your case, the reservoir maintains vacuum to the valve as the throttle plates open and vacuum falls off, extending the operating width of the valve. A check valve (also shown in the picture) lets vacuum build up in the reservoir, but not escape. This isolates ported vacuum from the EGR valve in one direction.
The EGR system always consists of an EGR spacer plate between the intake and carburetor, and an EGR valve on the plate to open and close exhaust flow into the combustion stream. The valve is vacuum operated. Most commonly the valve is controlled by ported vacuum through a temperature-controlled ported vacuum switch, such that the valve only opens during part throttle at full engine operating temperature.
In your case, the reservoir maintains vacuum to the valve as the throttle plates open and vacuum falls off, extending the operating width of the valve. A check valve (also shown in the picture) lets vacuum build up in the reservoir, but not escape. This isolates ported vacuum from the EGR valve in one direction.
