Meghan Hodges
The Chevy 350 engine is a classic, but maintaining its fuel delivery system is critical for performance and reliability. The fuel pump is central to this system, creating the pressure or suction needed to move fuel from the tank to the engine. While modern electric pumps are now common, the Chevy 350 typically came with a mechanical pump from the factory. This pump is belt-driven and is responsible for pumping air into the exhaust manifold to clear out heavy pollutants during idle. Over time, the pump can seize up, make noise, or simply look ugly and take up space. While it is illegal to remove the pump in most places, it can be done with relative ease, and some owners choose to do so, especially if they live in a state with no smog requirements.
| Characteristics | Values |
|---|---|
| Engine | Chevy 350 |
| Fuel pump function | Delivering gasoline from the tank to the carburetor or fuel injectors |
| Fuel pump types | Mechanical, Electric |
| Mechanical fuel pump function | Creates suction to draw fuel from the tank through the inlet valve |
| Electric fuel pump function | Spins an impeller or operates a diaphragm to push fuel forward under pressure |
| Air pump function | Pumping air into the exhaust manifold to clear out heavy pollutants during idle |
| Air pump removal | Remove bolts on the bottom side of the alternator bracket and the two bolts on the lower side |
| Air pump legality | Illegal to remove in the US and Canada, and may fail smog inspection |
| Fuel filter function | Traps contaminants before they reach the carburetor or injectors |
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What You'll Learn
Chevy 350 fuel pump types: mechanical vs. electric
The fuel pump is the heartbeat of the Chevy 350 engine, delivering gasoline from the tank to the carburetor or fuel injectors. The two main types of fuel pumps for the Chevy 350 engine are mechanical and electric.
Mechanical Fuel Pump
The mechanical fuel pump is the original design for carbureted engines. It mounts directly onto the engine block and utilizes an actuating lever or pushrod powered by the engine's camshaft. As the camshaft rotates, it physically pushes the pump arm up and down, creating a suction that draws fuel from the tank through the inlet valve. The downward stroke then pressurizes the fuel chamber, forcing gasoline out through the outlet valve and towards the carburetor. Spring pressure returns the lever.
Electric Fuel Pump
The electric fuel pump is a common upgrade or stock for later models of the Chevy 350. It is typically located at or near the fuel tank and uses a small motor to spin an impeller or operate a diaphragm, actively pushing fuel forward under pressure toward the engine. It requires a switched +12V power source. Fuel injection pumps are high-pressure, while carburetor-specific pumps generate lower pressure similar to mechanical pumps. A low-pressure electric pump mounted in the tank is common on many fuel-injected vehicles.
Comparison
Both mechanical and electric fuel pumps have their pros and cons, and the choice depends on the specific needs of the application. Mechanical pumps are generally more reliable but require more installation work. Electric pumps are more compact and powerful but are more expensive and less forgiving of poor installation practices.
Pollution Pump
The AIR (smog or pollution) pump is a supplementary emission control system that helps burn any fuel that made it past the combustion cycle and into the exhaust system. While removing emission equipment is illegal in most areas of the US and Canada, it is not typically a problem for off-road use and uninsured vehicles.
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How to remove the smog pump
It is important to note that removing emission equipment in the US and Canada is illegal in most areas. So, before you remove the smog pump, check with your local laws. For off-road use and uninsured types of vehicles, it is typically not a problem. This may include trailered 4X4s, track cars, and drag cars.
Now, if you have a 1984 Chevy van and want to remove the smog pump, you can do so by removing the whole pump and bracket assembly from the engine. First, remove the bolt on the bottom side of the alternator bracket and the two bolts on the lower side of the engine block. Don't forget the single vacuum line, electrical connector, and supply tube to the exhaust. On the exhaust supply tube, simply undo the hose clamp and pull off the rubber hose. You can also get a smaller belt and run the alternator on it. However, this might leave an open airway to the exhaust, which could affect performance.
If you have a G20 350, you can remove the smog pump and use a shorter belt, retaining the AC tension pulley. You can also get a bypass pulley to avoid having to get a different belt and possibly removing the tensioner under the AC.
If you have an S-10, the process is similar to the one described above. However, keep in mind that the pump is mounted low on the engine, so if you take your truck off-road and put it through water, the pump may not last long.
Removing the smog pump can be a simple process, but it is important to consider the potential impact on your vehicle's performance and legality before proceeding.
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The Chevy 350 fuel delivery system
The fuel tank is the reservoir that stores the gasoline. From the tank, steel or flexible hosed fuel lines transport the fuel. Older Chevy 350 models often featured a single main supply line, while newer systems may incorporate a return line. The fuel pump is the central, active component, generating the pressure or suction required to move the fuel. It can be mechanical or electric, with the original design being mechanical and newer models often featuring electric pumps. Mechanical pumps are mounted directly onto the engine block and utilise an actuating lever or pushrod powered by the engine's camshaft to create the necessary suction and pressurisation. Electric pumps, on the other hand, are typically located near the fuel tank and use a small motor to spin an impeller or operate a diaphragm, actively pushing fuel forward under pressure.
The fuel filter is a vital component that traps contaminants before the fuel reaches the carburettor or injectors. Finally, the carburettor or fuel injectors mix the fuel with air before it enters the engine's combustion chambers. Older Chevy 350s commonly used carburettors, while fuel injection became standard in later models.
Maintaining the fuel delivery system, particularly the fuel pump, is essential for optimal performance and reliability. Neglecting pump health can lead to issues such as engine stalling, hard starting, power loss, or complete engine failure. Upgrading to a modern electric fuel pump is an option, but it requires careful consideration and understanding of both pump types. Additionally, removing emission equipment, such as the AIR (smog) pump, is illegal in most areas of the US and Canada, so it is important to check local laws before making any modifications.
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Upgrading the fuel pump
The fuel pump is an essential component of the Chevy 350 engine, responsible for delivering fuel from the tank to the carburetor or fuel injectors. Upgrading to an electric fuel pump can significantly improve the performance, reliability, and longevity of your engine.
There are two main types of fuel pumps for the Chevy 350: mechanical and electric. Mechanical pumps were the original design, mounting directly onto the engine block and utilizing an actuating lever or pushrod powered by the engine's camshaft. However, they may struggle to meet the demands of modified engines or even aging stock systems. Electric fuel pumps, on the other hand, deliver consistent pressure and volume, preventing issues like lean conditions, vapor lock, and hard starting.
When upgrading to an electric fuel pump, it is crucial to match the pump's specifications to your engine's requirements. Consider the engine's performance tier and fuel pressure needs. Stock engines typically require 5-7 PSI fuel pressure, while high-performance builds with carburetors may need 6-8 PSI, and engines with EFI conversions demand 12-15 PSI. Additionally, calculate the flow needs: mild builds usually require 50-80 gallons per hour, while high-compression or forced-induction setups demand 100 GPH or more.
You have two options for installing an electric fuel pump: leaving the mechanical pump in place as a backup or removing it entirely. If you choose to leave the mechanical pump, install the electric pump by the tank. Otherwise, you can opt for a simpler solution by removing the mechanical pump and replacing it with the electric one, upgrading your entire fuel pump system at once.
Finally, consider the location of the electric pump. Mount the pump and fuel line away from heat sources, such as the exhaust, and keep it out of enclosed areas like the trunk or interior of your car. Mounting the pump in a high area will increase the workload, shortening its lifespan, so it is best to keep it in a low place, perhaps under the tank.
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The purpose of the smog pump
The smog pump, also known as the Air Pump or Air Injector Reactor (AIR) system, is an integral part of a vehicle's emission control mechanism. Its primary purpose is to reduce tailpipe emissions by blowing clean, pressurized oxygen into the exhaust stream near the exhaust manifold.
The smog pump specifically targets unburned hydrocarbons in the exhaust system. When the engine is cold, unburned fuel can exit through the exhaust. The smog pump introduces oxygen into the exhaust, allowing these hydrocarbons to continue burning as they move through the exhaust system and out of the tailpipe. This process helps to lower emissions and improve air quality.
The smog pump operates by forcing air through a series of components, including a diverter valve, a check valve, and an air injection manifold. During acceleration, air is directed into the exhaust stream, where it mixes with the exhaust gases, aiding in the combustion of any unused hydrocarbons. The diverter valve plays a crucial role in preventing backfires during deceleration by blocking airflow. When necessary, excess pressure is released into the air cleaner through the diverter valve.
While some consider the smog pump essential for reducing emissions, others view it as an unnecessary component that takes up valuable space in the engine compartment. Removing the smog pump is illegal in most areas of the US and Canada, but it is typically permissible for off-road use or uninsured vehicles. It is important to consult local laws before making any modifications to the emission control system.
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Frequently asked questions
Removing the pollution (smog) pump from your Chevy 350 involves removing the whole pump and bracket assembly from the engine. This includes removing bolts on the bottom side of the alternator bracket and the two bolts on the lower side of the engine block. You should also remove the single vacuum line, electrical connector, and supply tube to the exhaust.
The pollution pump, or AIR pump, is used as a supplementary emission control system. It helps burn any fuel that made it past the combustion cycle and into the exhaust system.
Over time, the pump can seize up, make noise, and take up a lot of room. Removing the pump declutters the engine bay and makes the engine look nicer.
In the US and Canada, removing emission equipment is illegal in most areas. It is a federal offense to remove factory-installed emission controls, except for replacements. However, for off-road use and uninsured vehicles, it is typically not an issue.
