Replacing Fuel Pump On A Bbc: Step-By-Step Guide

Replacing a fuel pump on a BBC engine can be a complex task, with many variables to consider. The type of fuel pump (mechanical or electric) and the performance requirements of the engine will influence the choice of pump and installation process. For example, a high-performance engine may require a different pump than a standard engine, and the use of nitrous oxide (NOS) may necessitate an additional electric pump. The clearance between the fuel pump and the engine cross-member is also a critical factor, as some pumps may not fit without modifications to the cross-member or the use of specific engine mounts. The fuel line size and material are other considerations, with options including aluminium, cupronickel, and braided PTFE hoses. When replacing a fuel pump, it is essential to select a compatible pump and carefully follow the installation instructions to ensure safe and proper operation.

Choosing the right fuel pump

Vehicle Horsepower and Fuel Consumption:

The amount of fuel your vehicle requires is determined by its horsepower and brake-specific fuel consumption (BSFC). Calculate your vehicle's maximum horsepower through dyno testing or by estimating based on the manufacturer's specifications and any aftermarket modifications. BSFC measures the amount of fuel consumed per unit of power produced. Generally, a typical gasoline engine will have a BSFC of less than one. However, this can vary depending on engine specifications, power adders, fuel type, and octane ratings.

Fuel Volume and Pressure:

Once you know your vehicle's horsepower and BSFC, you can calculate its fuel requirements using the following equations:

• Optimal lbs/hr = (Max. HP x BSFC)
• Optimal GPH = (Max. HP x BSFC) / 6
• Optimal LPH = (Max. HP x BSFC) / 1.585

Fuel Pump Type:

You also need to decide between a mechanical or electric fuel pump. Mechanical fuel pumps are typically mounted on the engine and were more common in older vehicles. Electric fuel pumps, on the other hand, are usually located inside the fuel tank and are more efficient, providing better fuel management. They are the standard in modern vehicles with electronic fuel injection systems.

Fuel Pump Quality and Reliability:

Look for a fuel pump that is crafted with high-grade materials and advanced manufacturing techniques to ensure durability and performance. A fuel pump that is designed to handle varying driving conditions, such as city drives, long highway stretches, or race tracks, will provide the most efficient and optimised fuel delivery.

Fuel Pump Testing:

Regular testing of your fuel pump is crucial to ensure optimal performance and identify any potential issues. Some factors to consider when testing include pressure levels, volume, electrical connections, noise and vibrations, fuel pump relay, leak checks, and operational lifespan.

Fuel Pump Maintenance and Replacement:

The longevity of your fuel pump depends on factors such as vehicle mileage, driving habits, fuel quality, and fuel filter maintenance. Keep an eye out for warning signs such as engine sputters at high speeds, loss of power during acceleration, engine stalling, whining noises from the fuel tank, and decreased fuel efficiency. Regular inspections by a qualified mechanic can also help identify potential problems.

Cost Considerations:

When considering a fuel pump replacement, factor in the cost of the part itself and labour for the installation. The price can vary depending on the vehicle model, year, and whether you choose an original equipment manufacturer (OEM) part or an aftermarket option.

By taking into account these factors and consulting with experienced professionals, you can make an informed decision on choosing the right fuel pump for your vehicle.

Replacing fuel lines

Firstly, it's important to assess the condition of your existing fuel lines. If they are damaged or excessively worn, it is recommended to replace them entirely. On the other hand, if they are simply clogged or contaminated, they can be cleaned or flushed out before reinstallation. It is also essential to ensure that your fuel lines are compatible with the type of fuel you are using, especially if you are switching to an alternative fuel source.

When choosing replacement fuel lines, it is crucial to select ones that are specifically designed for your vehicle's engine and fuel system. Consider the diameter of the lines, as well as the material they are made of. For example, options include aluminium, cupronickel, or stainless steel braided lines. The choice of material will impact factors such as corrosion resistance, flexibility, and fuel flow efficiency. It is also worth noting that fuel lines are available in different lengths to accommodate various engine configurations.

The next step is to carefully remove the old fuel lines, making sure to catch any spilled fuel in a suitable container and taking appropriate fire safety precautions. Once the old lines are removed, clean the surrounding area and inspect for any damage or leaks. It is also good practice to replace any gaskets, O-rings, or seals that show signs of wear or damage.

When installing the new fuel lines, pay close attention to the routing and ensure that they are securely fastened to prevent chafing or rubbing against other components. Use suitable clamps or fittings to secure the lines in place, and consider using protective sleeves or grommets in areas where the lines pass through the frame or come into contact with other components. Additionally, ensure that the lines are correctly clocked or oriented to avoid interference with other parts, such as the radiator hose.

Finally, before starting the engine, it is crucial to check for any leaks in the fuel system. Use soapy water or a leak detection solution to inspect all connections and joints for any signs of fuel leakage. Tighten any loose fittings as needed and re-check for leaks. Once you are confident that there are no leaks, start the engine and observe for any unusual behaviour or noises. Keep a close eye on fuel pressure and flow to ensure that the new lines are performing as expected.

Adjusting the clock on the pump

Understanding the Clocking Feature

The clocking feature on a fuel pump refers to the ability to rotate the pump's lower housing, which changes the orientation of the inlet and outlet fittings. This feature is especially useful when you need to adjust the fuel line routing to avoid interference with other components, such as the radiator hose.

Assessing the Need for Adjustment

Before adjusting the clock on your fuel pump, carefully examine the fuel line routing and identify any potential conflicts with other engine components. Look for areas where the fuel line may rub against another part or where it could be positioned more efficiently.

Loosening the Pump

To adjust the clock on the pump, you will need to first loosen it. Start by disconnecting the fuel lines from the inlet and outlet fittings. Be sure to have a rag or container ready to catch any fuel that may spill. Once the lines are disconnected, loosen the bolts that secure the pump to the engine. Do not remove the bolts completely; simply loosen them enough to allow the pump to rotate.

Rotating the Pump

With the bolts loosened, you can now rotate the pump to the desired position. Be mindful of the amount of adjustment needed to resolve the clearance issue. You may only need to rotate the pump slightly to achieve the necessary clearance. Once you have reached the desired position, tighten the bolts to secure the pump in place.

Reconnecting the Fuel Lines

After adjusting the clock on the pump, reconnect the fuel lines to the inlet and outlet fittings. Ensure that the lines are securely attached and free from any kinks or obstructions. Pay close attention to the routing of the lines to ensure they are clear of any potential hazards.

Testing and Final Adjustments

Once the fuel lines are reconnected, start the engine and check for any leaks around the pump and fuel lines. Also, pay attention to the fuel pressure gauge to ensure that the pump is functioning correctly. If any issues are identified, carefully inspect the pump and fuel lines for proper installation and secure connections. Make any necessary adjustments to ensure optimal performance and safety.

Electric vs mechanical pumps

When it comes to changing the fuel pump on a BBC, there are two main types to choose from: electric or mechanical. Each has its own advantages and considerations to keep in mind.

Mechanical fuel pumps have been a common choice for classic hot rods and muscle cars. They are mounted on the engine and actuated by a lever that rides on a fuel pump cam lobe, creating a suction that pulls fuel from the tank to the carburetor. Mechanical pumps are generally quiet and cannot be heard when pumping. They also have a pre-set fuel pressure that works well with typical carburetors. However, one downside is that they may not provide enough pressure and volume for fuel injection conversions. Additionally, since mechanical pumps only pump fuel when the engine is cranking, it can take longer to start a car if the fuel has evaporated from the carburetor.

On the other hand, electric fuel pumps are available for both carbureted and fuel-injected applications. They can be mounted externally or inside the fuel tank. Electric pumps push the fuel to the engine and must be mounted close to the tank and lower than it to ensure proper fuel supply. Electric pumps require a return or bypass regulator to control fuel pressure and can be noisier, depending on their design and installation. However, they have the advantage of priming the carburetor before starting the vehicle, which is useful for cars that sit for extended periods.

When deciding between an electric or mechanical fuel pump for a BBC, consider factors such as the type of fuel delivery system (carbureted or fuel injected), desired noise levels, and the specific requirements of your engine setup. Both options have their pros and cons, so it's important to choose the one that best suits your needs and application.

For a 500 hp BBC with an 80/20 Street/Strip setup, some experienced mechanics recommend a combination of a mechanical pump, such as the Carter 172, and an electric pump for the NOS. This setup ensures reliable fuel delivery for both street and strip use.

Fuel pump identification

Another way to identify a BBC fuel pump is by the part number. For example, AC Delco mechanical fuel pumps for Corvette big blocks have the GM part number #6415748. These pumps were recommended by Chevrolet for racing usage and can be identified by the stamped numbers 40170 or 40731 on the big blocks. Small blocks, on the other hand, have a metal tag with a stamped number and a cast aluminium bottom cover.

Physical characteristics can also help with identification. BBC fuel pumps tend to stick out from the block by 3/4" or more, indicating a high-performance pump. The pump arm is also a distinguishing feature; it should be noted that the \"W\" big-block and small-block pumps have the same arm. Additionally, big-block high-performance pumps typically use 3/8" lines.

When in doubt, it is always best to consult a professional or a trusted forum for advice on fuel pump identification.

Frequently asked questions