77 350 Automatic with A/C
Thread Starter
Racer
Joined: Apr 2006
Posts: 340
Likes: 0
From: Warrensburg MO
77 350 Automatic with A/C
I need some help here. Ported vacuum switch on the thermostat housing, three port. Two of the hoses on my car go to the carb, and the third one goes to the heat riser. After removing my carb for a rebuild, I noticed that the vacuum hose that runs from the front vacuum break is not connected. It looks like it should hook to a port that is currently being occupied by a hose from the ported vacuum switch. So my first question is, where do the three hoses from the switch on the thermostat housing go to?
The next question is..there is a factory adjustment in front of the power piston on my carb. My book says not to mess with it. Should I leave this alone, or go ahead and remove it for cleaning? The numbers on the carb match the car so I think it is the original carb. I have removed the top from the carb so you know my point of view. TIA
Tommy
The next question is..there is a factory adjustment in front of the power piston on my carb. My book says not to mess with it. Should I leave this alone, or go ahead and remove it for cleaning? The numbers on the carb match the car so I think it is the original carb. I have removed the top from the carb so you know my point of view. TIA
Tommy
Thread Starter
Racer
Joined: Apr 2006
Posts: 340
Likes: 0
From: Warrensburg MO
I need some help here. Ported vacuum switch on the thermostat housing, three port. Two of the hoses on my car go to the carb, and the third one goes to the heat riser. After removing my carb for a rebuild, I noticed that the vacuum hose that runs from the front vacuum break is not connected. It looks like it should hook to a port that is currently being occupied by a hose from the ported vacuum switch. So my first question is, where do the three hoses from the switch on the thermostat housing go to?
The next question is..there is a factory adjustment in front of the power piston on my carb. My book says not to mess with it. Should I leave this alone, or go ahead and remove it for cleaning? The numbers on the carb match the car so I think it is the original carb. I have removed the top from the carb so you know my point of view. TIA
Tommy
The next question is..there is a factory adjustment in front of the power piston on my carb. My book says not to mess with it. Should I leave this alone, or go ahead and remove it for cleaning? The numbers on the carb match the car so I think it is the original carb. I have removed the top from the carb so you know my point of view. TIA
Tommy
Race Director
Joined: Sep 2001
Posts: 10,560
Likes: 439
From: Wellington, FL
St. Jude Donor '11 thru '25
Look through the various Vette vendor catalogs and you might find one. You can do this by Googleing them one by one. Dr. Rebuild used to have them in his catalog. If you have the Chevy Shop Manual, you might find it there. Good luck. 
Thread Starter
Racer
Joined: Apr 2006
Posts: 340
Likes: 0
From: Warrensburg MO
Thread Starter
Racer
Joined: Apr 2006
Posts: 340
Likes: 0
From: Warrensburg MO
Tommy
Safety Car
Joined: Oct 2007
Posts: 4,384
Likes: 1,759
From: Seattle Area Washington
There are two (TVS) thermo vacuum switches in your system. One is located in the thermostat housing and one in the intake manifold. The TVS switch that is screwed into the thermostat housing may appear to have three nipples but actually one of them is the exhaust port for the EFE valve. The top port is vacuum from carburetor, middle port goes to the EFE valve and the bottom port is the exhaust port. The vacuum hose from the carburetor should be interrupted by an inline check valve before the hose enters the EFE TVS switch. The TVS switch screwed into the intake manifold has a vacuum line from the carburetor into the lower port of the TVS switch and the upper port then goes to the EGR valve.
I recommend two manuals; the first I would look for is the Green cover 1977 Chevrolet service manual e-bay is a good source and the 1977 Corvette assembly manual. Top picture is from the 1977 service manual, second picture is from the assembly manual. Second picture is the correct layout.
Brian
I recommend two manuals; the first I would look for is the Green cover 1977 Chevrolet service manual e-bay is a good source and the 1977 Corvette assembly manual. Top picture is from the 1977 service manual, second picture is from the assembly manual. Second picture is the correct layout.
Brian
Last edited by bmotojoe; Feb 25, 2008 at 01:45 PM.
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