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What are the two Plugins on the Thermostat Housing Used For?

   
Old Nov 29, 2021 | 02:19 PM
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What are the two Plugins on the Thermostat Housing Used For?
As seen in the attached photograph, what are they& purpose?
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Old Nov 29, 2021 | 03:05 PM
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Re: What are the two Plugins on the Thermostat Housing Used For?
Those are Vacuum Ports that are switched Open/ Closed, depending on the Engine Coolant Temperature.

They were used for the Vacuum Advance of the Distributor... and for Emissions control devices.

Are you using a 70s Era Small-Block in a Third-Gen?
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Old Nov 29, 2021 | 04:54 PM
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Re: What are the two Plugins on the Thermostat Housing Used For?
One on the left looks like the EFE valve, right...maybe for the air diverter valve.
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Old Nov 30, 2021 | 10:15 AM
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From: Windsor, On
Car: 1984 Trans AM
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Axle/Gears: 3.23
Re: What are the two Plugins on the Thermostat Housing Used For?
Stock 305 in an '84 Trans AM of a car that was built for the Canadian market - no ecm
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Old Nov 30, 2021 | 11:01 AM
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72buickgs
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From: Windsor, On
Car: 1984 Trans AM
Engine: 305
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Axle/Gears: 3.23
Re: What are the two Plugins on the Thermostat Housing Used For?
Originally Posted by vorteciroc
Those are Vacuum Ports that are switched Open/ Closed, depending on the Engine Coolant Temperature.

They were used for the Vacuum Advance of the Distributor... and for Emissions control devices.

Are you using a 70s Era Small-Block in a Third-Gen?
Why would u want to influence the vacuum advance? does it have to do with emissions?
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Old Nov 30, 2021 | 12:29 PM
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Re: What are the two Plugins on the Thermostat Housing Used For?
Originally Posted by 72buickgs
Why would u want to influence the vacuum advance? does it have to do with emissions?
Yes, it's for emissions. Retard the timing during warm up to heat the the o2 sensor and catalytic converters faster. Modern cars still do this, but it's through the ECM.
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