I have an 85 bronco xlt, 351w, c6 auto. I've removed the smog pump and the emissions junk. Put a new edelbrock carb on it. But now I have so many vacuum lines under the hood, I just wanna know what I can remove or the bare necessities (brakes, carb, etc) vacuum lines. Thanks
85 bronco 351w c6 vacuum lines
- Thread starter Scrotez
- Start date
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Yo Scrotez,
Welcome!
Keep:
For power brakes, keep the large vacuum line to booster.
And;
MAP Sensor
...
Thermostatic Air Inlet System
This system consists of a heat shroud which is integral with the right side exhaust manifold, a hot air hose and a special air cleaner assembly equipped with a thermal sensor and vacuum motor and air valve assembly.
The temperature of the carburetor intake air is thermostatically controlled by means of a valve plate and a vacuum override built into a duct assembly attached to the air cleaner. The exhaust manifold shroud tube is attached to the shroud over the exhaust manifold for the source of heated air.
The thermal sensor is attached to the air valve actuating lever, along with the vacuum motor lever, both of which control the position of the air valve to supply either heated air from the exhaust manifold or cooler air from the engine compartment.
During the warm-up period, when the under-the-hood temperatures are low, the thermal sensor doesn't exert enough tension on the air valve actuating lever to close (heat off) the air valve. Thus, the carburetor receives heated air from around the exhaust manifold.
As the temperature of the air entering the air cleaner approaches approximately 110°F (43°C), the thermal sensor begins to push on the air valve actuating lever and overcome the spring tension which holds the air valve in the open (heat on) position. The air valve begins to move to the closed (heat off) position, allowing only under-the-hood air to enter the air cleaner.
The air valve in the air cleaner will also open, regardless of the air temperature, during heavy acceleration to obtain maximum airflow through the air cleaner. The extreme decrease in intake manifold vacuum during heavy acceleration permits the vacuum motor to override the thermostatic control. This opens the system to both heated air and air from the engine compartment.
...
Positive Crankcase Ventilation System
...
Throttle Position Sensor
...
PVS valve (PVS) is a temperature sensing valve found on the distributor vacuum advance line, and is installed in the coolant outlet elbow. During prolonged periods of idle, or any other situation which causes engine operating temperatures to be higher than normal, the valve, which under normal conditions simply connects the vacuum advance diaphragm to its vacuum source within the carburetor, closes the normal source vacuum port and engages an alternate source vacuum port. This alternate source is from the intake manifold which, under idle conditions, maintains a high vacuum. This increase in vacuum supply to the distributor diaphragm advances the timing, increasing the idle speed. The increase in idle speed causes a directly proportional increase in the operation of the cooling system. When the engine has cooled sufficiently, the vacuum supply is returned to its normal source, the carburetor.
EGR/Coolant Spark Control System
The EGR/CSC system is used on most 1976 and later models. It regulates both distributor spark advance and the EGR valve operation according to coolant temperature by sequentially switching vacuum signals.
The major EGR/CSC system components are:
95°F (35°C) EGR/PVS valve;
Spark Delay Valve (SDV);
Vacuum check valve.
When the engine coolant temperature is below 82°F (28°C), the EGR/PVS valve admits carburetor EGR port vacuum (occurring at about 2,500 rpm) directly to the distributor advance diaphragm, through the one-way check valve.
At the same time, the EGR/PVS valve shuts off carburetor EGR vacuum to the EGR valve and transmission diaphragm.
When engine coolant temperature is 95°F (35°C) and above, the EGR/PVS valve is actuated and directs carburetor EGR vacuum to the EGR valve and transmission instead of the distributor. At temperatures between 82–95°F (28–35°C), the EGR/PVS valve may be open, closed, or in mid-position.
The SDV valve delay carburetor spark vacuum to the distributor advance diaphragm by restricting the vacuum signal through the SDV valve for a predetermined time. During normal acceleration, little or not vacuum is admitted to the distributor advance diaphragm until acceleration is completed, because of (1) the time delay of the SDV valve and (2) the rerouting of EGR port vacuum if the engine coolant temperature is 95°F (35°C) or higher.
The check valve blocks off vacuum signal from the SDV to the EGR/PVS so that carburetor spark vacuum will not be dissipated when the EGR/PVS is actuated above 95°F (35°C).
The 235°F (113°C) PVS is not part of the EGR/CSC system, but is connected to the distributor vacuum advance to prevent engine overheating while idling (as on previous models). At idle speed, no vacuum is generated at either the carburetor spark port or EGR port and engine timing is fully ********. When engine coolant temperature reaches 235°F (113°C), however, the valve is actuated to admit intake manifold vacuum to the distributor advance diaphragm. This advances the engine timing and speeds up the engine. The increase in coolant flow and fan speed lowers engine temperature.
...
The Evaporative Emission Control System provides a sealed fuel system with the capability to store and condense fuel vapors. The system has three parts: a fill control vent system; a vapor vent and storage system; and a pressure and vacuum relief system (special fill cap).
The fill control vent system is a modification to the fuel tank. It uses a dome air space within the tank which is 10-12% of the tank's volume. The air space is sufficient to provide for the thermal expansion of the fuel. The space also serves as part of the in-tank vapor vent system.
The in-tank vent system consists of the domed air space previously described and a vapor separator assembly. The separator assembly is mounted to the top of the fuel tank and is secured by a cam-lockring, similar to the one which secures the fuel sending unit. Foam material fills the vapor separator assembly. The foam material separates raw fuel and vapors, thus retarding the entrance of fuel into the vapor line.
The vapor separator is an orifice valve located in the dome of the tank. The restricted size of the orifice, 0.050 in. (1.27mm) tends to allow only vapor to pass out of the tank. The orifice valve is connected to the vent line which runs forward to the carbon filled canister in the engine compartment.
The sealed filler cap has a pressure-vacuum relief valve. Under normal operating conditions, the filler cap operates as a check valve, allowing air to enter the tank to replace the fuel consumed. At the same time, it prevents vapors from escaping through the cap. In case of excessive pressure within the tank, the filler cap valve opens to relieve the pressure.
Because the filler cap is sealed, fuel vapors have only one place through which they may escape: the vapor separator assembly at the top of the fuel tank. The vapors pass through the foam material and continue through a single vapor line which leads to a canister in the engine compartment. The canister is filled with activated charcoal.
Another vapor line runs from the top of the carburetor float chamber or the intake manifold, or the throttle body, to the charcoal canister.
As the fuel vapors (hydrocarbons), enter the charcoal canister, they are absorbed by the charcoal. The air is dispelled through the open bottom of the charcoal canister, leaving the hydrocarbons trapped within the charcoal. When the engine is started, vacuum causes fresh air to be drawn into the canister from its open bottom. The fresh air passes through the charcoal picking up the hydrocarbons which are trapped there and feeding them into the engine for burning with the fuel mixture.
****
Remove & Cap Lines to:
Thermactor Air Injection System to Catalytic Converter System
ost 1976-86 models are equipped with a Thermactor emission control system. The Thermactor emission control system makes use of a belt driven air pump to inject fresh air into the hot exhaust stream through the engine exhaust ports. The result is the extended burning of those fumes which were not completely ignited in the combustion chamber, and the subsequent reduction of the hydrocarbon and carbon monoxide content of the exhaust emissions into harmless carbon dioxide and water.
The Thermactor system is composed of the following components:
Air supply pump (belt driven)
Removal; "...What you need to do is electrically plug in the TAB and TAD solenoids but remove the vacuum lines, then all the air injection plumbing and valves can be removed and the heads plugged. The EGR is a seperate system from the Thermactor and the computer treats it very differently, it also helps increase milage and power so it's a good idea to keep it anyway.
Air control valves
Check valves
Air manifolds (internal or external)
Air supply tubes (on external manifolds only)
Air for the Thermactor system is cleaned by means of a centrifugal filter fan mounted on the air pump driveshaft. The air filter does not require a replaceable element.
To prevent excessive pressure, the air pump is equipped with a pressure relief valve which uses a replaceable plastic plug to control the pressure setting.
The pump supplies air under pressure, into the exhaust system thus lowering the exhaust emissions due to combustion. The belt driven air pump takes air in through an impeller-type centrifugal air filter fan, thus eliminating the need for a separate air filter. Dust and dirt particles cannot enter the pump because these heavier than air contaminants are thrown from the air intake by centrifugal force. The Thermactor air pump has sealed bearings which are lubricated for the life of the unit, and preset rotor vane and bearing clearances, which do not require any periodic adjustments.
The air supply from the pump is controlled by the air by-pass valve, sometimes called a dump valve. During deceleration, the air bypass valve opens, momentarily diverting the air supply through a silencer and into the atmosphere, thus preventing backfires within the exhaust system.
A check valve is incorporated in the air inlet side of the air manifolds. Its purpose is to prevent exhaust gases from backing up into the Thermactor system. This valve is especially important in the event of drive belt failure, and during deceleration, when the air by-pass valve is dumping the air supply.
The air manifolds and air supply tubes channel the air from the Thermactor air pump into the exhaust ports of each cylinder, thus completing the cycle of the Thermactor system.
...
Exhaust Gas Recirculation System
Cap all lines, use or make a block-off plate.
Vacuum Diagram:
Welcome!
Keep:
For power brakes, keep the large vacuum line to booster.
And;
MAP Sensor
...
Thermostatic Air Inlet System
This system consists of a heat shroud which is integral with the right side exhaust manifold, a hot air hose and a special air cleaner assembly equipped with a thermal sensor and vacuum motor and air valve assembly.
The temperature of the carburetor intake air is thermostatically controlled by means of a valve plate and a vacuum override built into a duct assembly attached to the air cleaner. The exhaust manifold shroud tube is attached to the shroud over the exhaust manifold for the source of heated air.
The thermal sensor is attached to the air valve actuating lever, along with the vacuum motor lever, both of which control the position of the air valve to supply either heated air from the exhaust manifold or cooler air from the engine compartment.
During the warm-up period, when the under-the-hood temperatures are low, the thermal sensor doesn't exert enough tension on the air valve actuating lever to close (heat off) the air valve. Thus, the carburetor receives heated air from around the exhaust manifold.
As the temperature of the air entering the air cleaner approaches approximately 110°F (43°C), the thermal sensor begins to push on the air valve actuating lever and overcome the spring tension which holds the air valve in the open (heat on) position. The air valve begins to move to the closed (heat off) position, allowing only under-the-hood air to enter the air cleaner.
The air valve in the air cleaner will also open, regardless of the air temperature, during heavy acceleration to obtain maximum airflow through the air cleaner. The extreme decrease in intake manifold vacuum during heavy acceleration permits the vacuum motor to override the thermostatic control. This opens the system to both heated air and air from the engine compartment.
...
Positive Crankcase Ventilation System
...
Throttle Position Sensor
...
PVS valve (PVS) is a temperature sensing valve found on the distributor vacuum advance line, and is installed in the coolant outlet elbow. During prolonged periods of idle, or any other situation which causes engine operating temperatures to be higher than normal, the valve, which under normal conditions simply connects the vacuum advance diaphragm to its vacuum source within the carburetor, closes the normal source vacuum port and engages an alternate source vacuum port. This alternate source is from the intake manifold which, under idle conditions, maintains a high vacuum. This increase in vacuum supply to the distributor diaphragm advances the timing, increasing the idle speed. The increase in idle speed causes a directly proportional increase in the operation of the cooling system. When the engine has cooled sufficiently, the vacuum supply is returned to its normal source, the carburetor.
EGR/Coolant Spark Control System
The EGR/CSC system is used on most 1976 and later models. It regulates both distributor spark advance and the EGR valve operation according to coolant temperature by sequentially switching vacuum signals.
The major EGR/CSC system components are:
95°F (35°C) EGR/PVS valve;
Spark Delay Valve (SDV);
Vacuum check valve.
When the engine coolant temperature is below 82°F (28°C), the EGR/PVS valve admits carburetor EGR port vacuum (occurring at about 2,500 rpm) directly to the distributor advance diaphragm, through the one-way check valve.
At the same time, the EGR/PVS valve shuts off carburetor EGR vacuum to the EGR valve and transmission diaphragm.
When engine coolant temperature is 95°F (35°C) and above, the EGR/PVS valve is actuated and directs carburetor EGR vacuum to the EGR valve and transmission instead of the distributor. At temperatures between 82–95°F (28–35°C), the EGR/PVS valve may be open, closed, or in mid-position.
The SDV valve delay carburetor spark vacuum to the distributor advance diaphragm by restricting the vacuum signal through the SDV valve for a predetermined time. During normal acceleration, little or not vacuum is admitted to the distributor advance diaphragm until acceleration is completed, because of (1) the time delay of the SDV valve and (2) the rerouting of EGR port vacuum if the engine coolant temperature is 95°F (35°C) or higher.
The check valve blocks off vacuum signal from the SDV to the EGR/PVS so that carburetor spark vacuum will not be dissipated when the EGR/PVS is actuated above 95°F (35°C).
The 235°F (113°C) PVS is not part of the EGR/CSC system, but is connected to the distributor vacuum advance to prevent engine overheating while idling (as on previous models). At idle speed, no vacuum is generated at either the carburetor spark port or EGR port and engine timing is fully ********. When engine coolant temperature reaches 235°F (113°C), however, the valve is actuated to admit intake manifold vacuum to the distributor advance diaphragm. This advances the engine timing and speeds up the engine. The increase in coolant flow and fan speed lowers engine temperature.
...
The Evaporative Emission Control System provides a sealed fuel system with the capability to store and condense fuel vapors. The system has three parts: a fill control vent system; a vapor vent and storage system; and a pressure and vacuum relief system (special fill cap).
The fill control vent system is a modification to the fuel tank. It uses a dome air space within the tank which is 10-12% of the tank's volume. The air space is sufficient to provide for the thermal expansion of the fuel. The space also serves as part of the in-tank vapor vent system.
The in-tank vent system consists of the domed air space previously described and a vapor separator assembly. The separator assembly is mounted to the top of the fuel tank and is secured by a cam-lockring, similar to the one which secures the fuel sending unit. Foam material fills the vapor separator assembly. The foam material separates raw fuel and vapors, thus retarding the entrance of fuel into the vapor line.
The vapor separator is an orifice valve located in the dome of the tank. The restricted size of the orifice, 0.050 in. (1.27mm) tends to allow only vapor to pass out of the tank. The orifice valve is connected to the vent line which runs forward to the carbon filled canister in the engine compartment.
The sealed filler cap has a pressure-vacuum relief valve. Under normal operating conditions, the filler cap operates as a check valve, allowing air to enter the tank to replace the fuel consumed. At the same time, it prevents vapors from escaping through the cap. In case of excessive pressure within the tank, the filler cap valve opens to relieve the pressure.
Because the filler cap is sealed, fuel vapors have only one place through which they may escape: the vapor separator assembly at the top of the fuel tank. The vapors pass through the foam material and continue through a single vapor line which leads to a canister in the engine compartment. The canister is filled with activated charcoal.
Another vapor line runs from the top of the carburetor float chamber or the intake manifold, or the throttle body, to the charcoal canister.
As the fuel vapors (hydrocarbons), enter the charcoal canister, they are absorbed by the charcoal. The air is dispelled through the open bottom of the charcoal canister, leaving the hydrocarbons trapped within the charcoal. When the engine is started, vacuum causes fresh air to be drawn into the canister from its open bottom. The fresh air passes through the charcoal picking up the hydrocarbons which are trapped there and feeding them into the engine for burning with the fuel mixture.
****
Remove & Cap Lines to:
Thermactor Air Injection System to Catalytic Converter System
ost 1976-86 models are equipped with a Thermactor emission control system. The Thermactor emission control system makes use of a belt driven air pump to inject fresh air into the hot exhaust stream through the engine exhaust ports. The result is the extended burning of those fumes which were not completely ignited in the combustion chamber, and the subsequent reduction of the hydrocarbon and carbon monoxide content of the exhaust emissions into harmless carbon dioxide and water.
The Thermactor system is composed of the following components:
Air supply pump (belt driven)
Removal; "...What you need to do is electrically plug in the TAB and TAD solenoids but remove the vacuum lines, then all the air injection plumbing and valves can be removed and the heads plugged. The EGR is a seperate system from the Thermactor and the computer treats it very differently, it also helps increase milage and power so it's a good idea to keep it anyway.
Air control valves
Check valves
Air manifolds (internal or external)
Air supply tubes (on external manifolds only)
Air for the Thermactor system is cleaned by means of a centrifugal filter fan mounted on the air pump driveshaft. The air filter does not require a replaceable element.
To prevent excessive pressure, the air pump is equipped with a pressure relief valve which uses a replaceable plastic plug to control the pressure setting.
The pump supplies air under pressure, into the exhaust system thus lowering the exhaust emissions due to combustion. The belt driven air pump takes air in through an impeller-type centrifugal air filter fan, thus eliminating the need for a separate air filter. Dust and dirt particles cannot enter the pump because these heavier than air contaminants are thrown from the air intake by centrifugal force. The Thermactor air pump has sealed bearings which are lubricated for the life of the unit, and preset rotor vane and bearing clearances, which do not require any periodic adjustments.
The air supply from the pump is controlled by the air by-pass valve, sometimes called a dump valve. During deceleration, the air bypass valve opens, momentarily diverting the air supply through a silencer and into the atmosphere, thus preventing backfires within the exhaust system.
A check valve is incorporated in the air inlet side of the air manifolds. Its purpose is to prevent exhaust gases from backing up into the Thermactor system. This valve is especially important in the event of drive belt failure, and during deceleration, when the air by-pass valve is dumping the air supply.
The air manifolds and air supply tubes channel the air from the Thermactor air pump into the exhaust ports of each cylinder, thus completing the cycle of the Thermactor system.
...
Exhaust Gas Recirculation System
Cap all lines, use or make a block-off plate.
Vacuum Diagram:
Last edited by a moderator:
Seabronc
New member
Here is what I left on my 85 351W. I consider it the bare minimum, reasons later if you are interested.
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Seabronc
New member
Obviously this requires that the components still exist and function. Also you need to understand the vacuum diagram. On a Bronco, only 1/2 of the purge system exist since it only has a single gas tank. The components shown in the diagram are in the relative position as they exist on the engine block.
The orange lines are those that control what use to be called the heat riser ( Exhaust Heat Control Valve). The EHCV use to be a spring valve on older engines located on the driver side exhaust pipe. The combination of the EHCV and the C/O HCV located on the intake to the right of the carburetor now perform the function of the spring operated valve. This system in combination with the Air Cleaner Diverter Valve,(A/CL DV) and Air cleaner Bi Metal, (A/C BI MET) valves are used to give the engine smooth operation while warming up to operating temperature. This is what gives the engine a smooth start and run characteristic, especially in the Winter when the engine is very cold. On cold Northern mornings this means the difference between being able to hop in the truck, start it and be able to immediately drive off while the engine is still cold. Without it the truck will usually have to set and warm up close to normal operating temperature before it will move with out stalling. Vacuum for these functions (RED lines) is supplied by the vacuum trees, one located at the front of the intake manifold and one at the rear, (it doesn't actually matter which vacuum tree you use, they both tap into the intake manifold. I ended up just using the rear vacuum tree). The rear vacuum tree supplies the brake booster and transmission vacuum lines as well.
The Vacuum Control Valves, (VCV), shown at the bottom right of the diagram are located on the front of the intake manifold, just behind the water neck where the heater hose hooks up. I dcid not use the VCV that is mounted on the top of the water neck since that is the connection to the EGR valve and is not in use, (the VCV can be removed and be replaced with a threaded plug).
The yellow line is the connection to the distributor from the carb "S" port for the vacuum advance function.
The gray line supplies vacuum when the engine first starts to **** off the fuel vapors trapped in the carbon canister. I suggest keeping this function as the carbon canister is like a relief valve for the gas tank to prevent it from over expanding on hot days as well as allowing the tank pressure to equalize to the outside pressure as fuel is sucked into the carb, (preventing the tank from developing negative pressure.
The before and after diagrams.
Hope this isn't too confusing
>-
The orange lines are those that control what use to be called the heat riser ( Exhaust Heat Control Valve). The EHCV use to be a spring valve on older engines located on the driver side exhaust pipe. The combination of the EHCV and the C/O HCV located on the intake to the right of the carburetor now perform the function of the spring operated valve. This system in combination with the Air Cleaner Diverter Valve,(A/CL DV) and Air cleaner Bi Metal, (A/C BI MET) valves are used to give the engine smooth operation while warming up to operating temperature. This is what gives the engine a smooth start and run characteristic, especially in the Winter when the engine is very cold. On cold Northern mornings this means the difference between being able to hop in the truck, start it and be able to immediately drive off while the engine is still cold. Without it the truck will usually have to set and warm up close to normal operating temperature before it will move with out stalling. Vacuum for these functions (RED lines) is supplied by the vacuum trees, one located at the front of the intake manifold and one at the rear, (it doesn't actually matter which vacuum tree you use, they both tap into the intake manifold. I ended up just using the rear vacuum tree). The rear vacuum tree supplies the brake booster and transmission vacuum lines as well.
The Vacuum Control Valves, (VCV), shown at the bottom right of the diagram are located on the front of the intake manifold, just behind the water neck where the heater hose hooks up. I dcid not use the VCV that is mounted on the top of the water neck since that is the connection to the EGR valve and is not in use, (the VCV can be removed and be replaced with a threaded plug).
The yellow line is the connection to the distributor from the carb "S" port for the vacuum advance function.
The gray line supplies vacuum when the engine first starts to **** off the fuel vapors trapped in the carbon canister. I suggest keeping this function as the carbon canister is like a relief valve for the gas tank to prevent it from over expanding on hot days as well as allowing the tank pressure to equalize to the outside pressure as fuel is sucked into the carb, (preventing the tank from developing negative pressure.
The before and after diagrams.
Hope this isn't too confusing
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