Chevy 350 Engine Vacuum Diagram
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Discussion Starter · #1 ·
Anyone know where I can get a vacuum diagram for my 1974 350 with the original two-barrel carb? My Chilton's book doesn't have it in there. Need help. Thanks
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Been looking for one myself. I can't find one anywhere. Best thing to do is just ask about each individual hose.
Are you replacing all of yours?
I'll try to draw something up today about my lines. They should be identical to yours.
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Discussion Starter · #3 ·
I'm restoring the car, I put the numbers matching motor back in with the two-barrel. When I bought the car a year ago, it had a 4 bolt 350 truck motor with a four barrel carb on it. I don't know what the vacuum routing is with the two barrel. It also has the EGR mounted on the intake. The carb is a rochester with two ports on the back, two on the right front corner, and one on the front of carb.
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Hi 7T4-SOA,
I have several old manuals but the vacuum hose routing diagrams in them only date back to 75 or 76. I don't know if GM even published diagrams for the earlier years.
I swapped a 4bbl onto the 350 in my 74 but I still have the original 2bbl intake/carb sitting in the garage. The vacuum hoses on it are hooked up as follows:
One of the two small ports on the back of the carb has a short hose that goes to the choke pull-off on the carb. The other small port has a longer hose that goes up to the ThermAC air cleaner. There's also a large plugged off port on the rear/center of the carb that would be used for power brakes (if equipped).
The top right front port goes to the distributor vacuum advance. Mine doesn't have it, but I think some of these cars were equipped with a TCS (transmission controlled spark) system that placed an electric solenoid valve inline with this hose.
The lower right front port goes to a TVS (thermal vacuum switch) located on the thermostat housing. From there another hose goes to the EGR valve.
The port on the front of the carb should be a little larger than the others (around 1/4" I think). It goes to the "CARB" port on the fuel evaporation canister that's mounted off to the left of the radiator. The "TANK" port on that canister obviously connects back to the gas tank vent.
The PCV valve on the 2bbl connects to a port on the left side of the manifold just below the carburetor. And if your car has an automatic transmission and/or AC, those connect to a fitting that screws into the intake behind the carb.
Depending on the emissions requirements of where the car was sold new, I think some may have had AIR (air injection reaction) aka smog pumps too. Those have a vacuum operated diverter valve. Mine didn't have that so I'm not sure where that hooks up.
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Discussion Starter · #5 ·
Thanks Ray, you explained everything I needed for my set up. I'm starting the car up tomorrow for the first time since rebuild. Your set up is exactly as mine, Thank You Very Much.
Source: https://www.stevesnovasite.com/threads/vacuum-diagram-for-a-350.113659/
Posted by: burtlittlefielde012473.blogspot.com
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