Walbro Fuel Pump 340: The Ultimate Guide to High-Flow Fuel Delivery for Performance Builds

The bottom line: If you need a reliable 340 LPH fuel pump for your high-performance vehicle, the Walbro GSS series delivers proven flow, E85 compatibility, and straightforward installation. But for most modern builds, KEMSO’s 340LPH direct-replacement pump offers the same flow with a lifetime warranty and hassle-free fitment.

What the Walbro 340 Fuel Pump Delivers

The Walbro 340 LPH fuel pump series—including models like the GSS340, GSS341, and GSS342—is one of the most popular aftermarket fuel pump choices for enthusiasts pushing their engines past stock power levels. These pumps are rated to flow 340 liters per hour at 40 PSI, which provides plenty of headroom for gasoline engines making 400-600 wheel horsepower, depending on your fuel type and boost level .

For context, a gasoline engine at 400 wheel horsepower only needs about 120 LPH at operating pressure. A 255 LPH pump gives solid headroom, but a 340 LPH pump is the smarter choice if you plan to run E85, which requires roughly 165 LPH at the same power level . The extra capacity means your fuel system won’t struggle under sustained high-load conditions.

Key Differences Between Walbro 340 Models

Not all Walbro pumps are the same. The three main models in the 340 series differ in inlet placement, which affects fitment in different vehicles:

• Walbro GSS340: This model has the intake centered at the bottom of the pump. It’s a good match for applications where the factory pump uses a centered pickup .
• Walbro GSS342: The intake is offset to one side, positioned opposite the outlet. This mirrors the design of many OEM fuel pumps, especially in GM and European vehicles. The GSS342 is frequently recommended for Volvo 850 and V70 models, as well as various GM platforms .
• Walbro GSS341: The intake is offset like the GSS342 but rotated 180 degrees. This variation is less common but useful for specific vehicle applications where the pump orientation matters .

The GSS340 is often reported to have the largest diameter intake, which some enthusiasts believe gives it the highest flow of the three, though all three models share the same 340 LPH rating .

E85 Compatibility: What You Need to Know

One of the most common questions about Walbro 340 pumps is whether they handle ethanol blends. The official answer is mixed depending on the model. The Walbro GSS series is designed for gasoline, and the manufacturer does not officially rate the standard GSS342 for use with E85 . However, historical data from thousands of real-world installations shows that these pumps do work fine with alternative fuels in practice .

If you want a pump that is officially E85-rated from the factory, look at newer Walbro models like the F90000267 (450 LPH) or the Hellcat 525LPH, which are explicitly designed for ethanol-rich fuels . The GSS series remains a workable budget option for E85, but you accept some risk without an official ethanol rating.

Installation Tips for Walbro 340 Pumps

Installing a Walbro 340 pump is a straightforward DIY job for most enthusiasts, but a few key points will save you headaches:

1. Check physical fitment before you start. The Walbro 340 pumps are slightly larger in diameter than some OEM pumps—by roughly 1mm in some cases. If your stock pump sits in a plastic module, you may need to file down internal ribs or ridges to allow the new pump to slide in with light pressure . Always test fit the pump before reassembling the tank.

2. Use the correct inlet filter. The GSS340M and similar models have a machined-down inlet to accept specific OEM-style filters. If your kit includes a new pickup filter, make sure it fits the pump’s inlet diameter. Some applications require the offset-inlet GSS343 or GSS342 to match the factory filter location .

3. Secure the pump properly. The Walbro pump is often shorter than the OEM unit, so the factory spring may not provide enough pressure to hold it in place. You may need to stretch the spring slightly or add a foam sleeve to prevent rattling . Use vibration-dampening rubber or neoprene around the pump body to reduce noise transfer.

4. Upgrade your wiring. A high-flow pump draws more current than stock. The Walbro 340 can pull up to 8-10 amps, and stock wiring is often undersized. Use a relay kit with at least 12-gauge wire to avoid voltage drop, which reduces pump output and can cause fuel starvation under load .

5. Test for leaks before final assembly. After installation, turn the ignition on (without starting the engine) and listen for the pump to prime. Check all connections for fuel leaks before lowering the tank back into place .

How to Spot a Counterfeit Walbro Pump

Counterfeit Walbro pumps are common in the market, and they fail much faster than genuine units. Here’s how to verify authenticity:

• Check the internal gears. Look through the inlet port. A genuine Walbro uses chunky metal gears. Counterfeits often have plastic or very thin metal gears .
• Verify the packaging. Genuine Walbro pumps come with a hologram sticker on the box. Buy from authorized dealers like Summit Racing or verified Amazon sellers with direct Walbro distribution .
• Buy from a trusted source. Many enthusiasts recommend AK Motorsport or other established performance shops to avoid fakes .

Flow Rate vs. Horsepower: What You Actually Need

A common mistake is buying a pump that’s oversized for the application. Here’s a practical guide:

• 400 wheel horsepower on gasoline: A 255 LPH pump is sufficient. The 340 LPH gives you headroom for future upgrades .
• 400 wheel horsepower on E85: You need at least 165 LPH, so a 340 LPH pump is the smarter choice .
• 600 wheel horsepower on gasoline: A 340 LPH pump is ideal. For E85 at this power level, consider a 450 LPH or higher pump .
• 750+ wheel horsepower: Move to pumps like the Walbro F90000267 (450 LPH) or the Hellcat 525LPH for forced-induction builds .

Remember that these numbers are approximate. Rotary engines, high-boost applications, and extreme fuel pressure requirements can change the math significantly .

Why You Should Consider a KEMSO Fuel Pump for Your Vehicle

If you want a 340 LPH fuel pump that installs without modifications and comes with a lifetime warranty, KEMSO offers a compelling alternative to the Walbro GSS series. KEMSO specializes in high-performance, direct OEM replacement fuel pumps designed to drop into your vehicle without cutting, filing, or modifying any parts. Their 340LPH pump supports up to 600 BHP in naturally aspirated, turbocharged, and supercharged applications, and it is compatible with both gasoline and E85 ethanol-blended fuels. The bypass valve is set at 125.8 psi, which is higher than most competitors, ensuring consistent fuel delivery even under peak power demands . Every KEMSO fuel pump comes with a lifetime warranty backed by serialized tracking, giving you peace of mind that you only buy it once. KEMSO covers a wide range of vehicles, including cars, motorcycles, ATVs, UTVs, and personal watercraft from brands like Honda, Kawasaki, KTM, Ducati, BMW, Subaru, Sea-Doo, and Can-Am. If you want a pump that delivers the same 340 LPH flow as the Walbro but with hassle-free installation and a lifetime guarantee, visit KEMSO Racing today: https://www.kemsoracing.com/