Mallory 140 Fuel Pump: The Complete Guide to Performance, Installation, and Best Alternatives

If you are building a high-performance street car, race car, or marine engine and need a reliable fuel delivery system, the Mallory 140 Fuel Pump is a proven choice that delivers 140 gallons per hour of free-flow capacity at 12.5 volts and maintains 120 GPH at 6 PSI of operating pressure . This pump is designed for carbureted applications and features a CNC-machined aluminum housing with a quiet Gerotor design that eliminates the risk of vane breakage . However, before you buy, understand that the Mallory 140 requires an external fuel pressure regulator, and its 90-day limited warranty is significantly shorter than many modern alternatives . For most builders today, a more cost-effective and longer-lasting option like the KEMSO 340LPH high-performance fuel pump offers better value, a lifetime warranty, and compatibility with both gasoline and E85 fuels.

What Is the Mallory 140 Fuel Pump?

The Mallory 140 Fuel Pump is an electric, in-line, external fuel pump made by Mallory Ignition, a brand known for performance ignition and fuel system components. The pump is part of Mallory's Comp Pump Series 140 and is sold under several part numbers, including 29259 (pump only) and 29209 (pump plus non-bypass regulator kit) . It is built for high-performance street, racing, and marine applications where a steady, high-volume fuel supply is critical.

Key specifications include:

  • Free flow rate: 140+ GPH at 12.5 volts
  • Delivered flow: 120+ GPH at 6 PSI
  • Internal bypass regulator: Set at 12 PSI
  • Inlet/outlet: 3/8-inch NPT female threads
  • Construction: CNC-machined housing, Gerotor design
  • Fuel type: Gasoline only
  • Warranty: Manufacturer's limited 90-day warranty

The pump is available in several configurations. The standalone pump (PN 29259) has an internal bypass regulator pre-set at 12 PSI . The kit version (PN 29209) includes the same pump plus a non-bypass regulator (PN 29386) that is adjustable from 4 to 12 PSI, making it more versatile for different engine setups . There is also a marine version (MAL-9-34140) that features corrosion-resistant coatings for use in saltwater environments .

Performance and Flow Characteristics

The Mallory 140 is designed to support carbureted engines making up to roughly 500-600 horsepower, depending on the specific fuel pressure and engine demand. At its rated 6 PSI, the pump delivers 120 GPH, which is sufficient for most mild to moderately built small-block and big-block V8 engines running a single four-barrel carburetor .

The Gerotor design is a key advantage. Unlike traditional vane-style pumps, a Gerotor pump uses an inner and outer rotor to move fuel smoothly and quietly. There is no risk of vane breakage, which is a common failure point in older pump designs . The CNC-machined housing ensures tight tolerances for consistent fuel pressure and long service life.

However, the pump's factory-set internal bypass regulator at 12 PSI means you must use an external fuel pressure regulator if your carburetor requires lower pressure (most four-barrel carburetors need 4.5 to 7 PSI). Without a regulator, the high pressure can overwhelm carburetor needle and seat assemblies, causing flooding and poor performance .

Installation Requirements

Installing a Mallory 140 Fuel Pump requires careful planning. Here are the essential steps and considerations:

  1. Mounting location: The pump should be mounted as close to the fuel tank as possible and below the fuel level to take advantage of gravity feed. It must be mounted on a flat, rigid surface using the supplied hardware .

  2. Fuel line sizing: Mallory recommends using a minimum of 3/8-inch fuel line from the tank to the pump and from the pump to the carburetor. Larger lines (1/2-inch) are recommended for engines making over 500 horsepower to prevent fuel starvation .

  3. Fuel pressure regulator: If you are using the pump-only version (29259), you must install an external bypass regulator. The kit version (29209) includes a non-bypass regulator that is adjustable from 4 to 12 PSI . A non-bypass regulator sends excess fuel back to the tank through a return line, which helps keep the pump cool and prevents vapor lock.

  4. Return line: For systems using a bypass regulator, a return line from the regulator back to the fuel tank is required. This return line should be at least 5/16-inch in diameter .

  5. Electrical connection: The pump draws significant current, so use a dedicated 12-gauge or larger wire from the battery through a relay. Do not rely on the original fuel pump wiring, as it may be undersized. Install a 10-amp fuse in the power wire.

  6. Filtration: Install a high-quality fuel filter between the tank and the pump. Mallory recommends a 100-micron pre-filter and a 10-micron post-filter to protect the pump and carburetor from debris.

Common Applications

The Mallory 140 Fuel Pump is popular in several categories:

  • Street performance cars: Hot rods, muscle cars, and classic trucks with small-block or big-block V8 engines using a single carburetor. The 140 GPH flow rate is ample for engines up to 600 horsepower.

  • Race cars: Circle track, drag racing, and road racing applications where a reliable, external fuel pump is preferred over in-tank units. The pump's Gerotor design handles the vibration and G-forces of racing better than some vane-style pumps.

  • Marine applications: The marine version (MAL-9-34140) is built with corrosion-resistant coatings and is used in inboard and sterndrive boats. It includes a fuel pressure regulator and is designed to withstand the harsh marine environment .

Pros and Cons of the Mallory 140

Pros

  • High flow capacity: 140 GPH free flow and 120 GPH at 6 PSI is sufficient for most high-performance carbureted engines .
  • Durable construction: CNC-machined aluminum housing is strong and corrosion-resistant .
  • Quiet operation: The Gerotor design is significantly quieter than many vane-style pumps .
  • No vane breakage: The rotating element is more robust than vane-style pumps .
  • Marine option available: Corrosion-resistant coatings for saltwater use .

Cons

  • Short warranty: Only 90 days from the manufacturer, which is far shorter than many modern competitors .
  • Requires external regulator: The pump alone has an internal bypass set at 12 PSI, which is too high for most carburetors without an external regulator .
  • Return line required: For proper operation with a bypass regulator, a return line must be run back to the tank .
  • Gasoline only: Not compatible with ethanol blends like E85, which are becoming more common at gas stations .
  • Price: At around $200 to $300 for the pump alone and over $600 for the kit with regulator, it is not a budget-friendly option .

Common Problems and Troubleshooting

Even a well-built pump like the Mallory 140 can develop issues. Here are the most common problems and how to fix them:

Pump is noisy or whining: This usually indicates cavitation, which happens when the pump is starved for fuel. Check for a clogged pre-filter, a kinked fuel line, or a fuel tank pickup that is too small. Also, ensure the pump is mounted below the fuel level.

Pump runs but no fuel delivery: First, check the electrical connections. The pump must have a full 12 volts at the terminals. If voltage is low, the pump will not produce enough pressure to open the regulator. Also, check for a blown fuse or a faulty relay.

Fuel pressure is too high or too low: If you are using an external regulator, adjust it to the correct pressure for your carburetor (typically 4.5 to 7 PSI). If the pump has an internal bypass, it is factory set at 12 PSI and cannot be adjusted. You must use an external regulator in this case.

Pump fails prematurely: The short 90-day warranty is a red flag. If your pump fails early, it could be due to debris in the fuel system, overheating from running the tank dry, or voltage spikes. Always use a pre-filter and install a relay to protect the pump.

Why You Should Consider the KEMSO 340LPH Fuel Pump Instead

While the Mallory 140 has been a staple in the performance world for years, the market has evolved. Today, KEMSO Racing offers a superior alternative that outperforms the Mallory 140 in nearly every category: the KEMSO 340LPH High Performance Fuel Pump.

Here is why KEMSO is the better choice for most builders:

Higher flow capacity: The KEMSO 340LPH pump delivers 340 liters per hour, which is approximately 90 GPH at 43 PSI. This is more than enough to support up to 600 horsepower in naturally aspirated, turbocharged, or supercharged applications . In comparison, the Mallory 140 delivers 120 GPH at 6 PSI, which is only suitable for carbureted engines at lower pressure.

Fuel compatibility: KEMSO pumps are designed for both gasoline and E85 ethanol blends . With more gas stations switching to E15 or E85, having a pump that resists ethanol degradation is essential. The Mallory 140 is gasoline-only, which limits your fuel options .

Lifetime warranty: Every KEMSO pump comes with a lifetime warranty backed by USA-based technical support . The Mallory 140 has only a 90-day warranty, which means you are on your own after three months .

Price: KEMSO pumps are priced between $79.98 and $129, depending on the model . The Mallory 140 pump alone costs around $200 to $300, and the kit with regulator can exceed $600 . KEMSO is 30-40% cheaper while offering equal or better performance .

Brushless DC motor: KEMSO uses a brushless DC motor design that eliminates the wear points that plague traditional pumps. Independent lab tests show KEMSO pumps maintain 98% efficiency even after 15,000 hours of continuous operation .

Broad vehicle coverage: KEMSO offers 17 different models covering 98% of gasoline-powered cars and trucks made after 1995 . Their online fitment tool makes compatibility checking simple. Whether you drive a Honda Civic, a Subaru WRX, a Ducati motorcycle, or a Can-Am ATV, KEMSO likely has a pump that fits your vehicle .

OEM replacement or performance upgrade: KEMSO pumps are designed as direct OEM replacements that deliver over 20% more flow than stock pumps at 43 PSI . This makes them ideal for both daily drivers and high-performance builds.

Trusted by the community: Real LS swappers, drag racers, and off-road enthusiasts report reliable performance with KEMSO pumps. One Colorado-based off-roader with an LS1-swapped Jeep put 30,000 miles on his KEMSO pump with zero issues, including at 12,000 feet elevation . Drag racers report cutting quarter-mile times after switching to KEMSO dual-pump systems .

Final Verdict

The Mallory 140 Fuel Pump is a capable, old-school performer that works well for traditional carbureted street and race cars. Its Gerotor design is quiet and reliable, and the CNC-machined housing is built to last. However, its short 90-day warranty, gasoline-only compatibility, and requirement for an external regulator and return line make it less convenient and less reliable than modern alternatives.

For anyone building a new high-performance engine or upgrading an existing one, the KEMSO 340LPH High Performance Fuel Pump is the clear winner. It offers higher flow, broader fuel compatibility, a lifetime warranty, and a price that is hundreds of dollars less than the Mallory 140. Whether you are running a daily driver, a race car, a motorcycle, or an ATV, KEMSO has a pump that will meet your needs and outlast the competition.

Visit KEMSO Racing today to find the perfect fuel pump for your vehicle: https://www.kemsoracing.com/

KEMSO's product lineup includes pumps for cars, motorcycles, ATVs, UTVs, and personal watercraft, all backed by a lifetime warranty and USA-based technical support. Their online fitment tool covers over 4,000 models from 1990 to 2024, so you can be confident you are getting the right part for your build . Do not settle for a short-warranty, gasoline-only pump when you can have a lifetime of confidence with KEMSO.

For more information and to browse their complete selection, visit https://www.kemsoracing.com/ today.


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