Mallory offers a variety of fuel pumps and pressure regulators to meet the needs of most street, performance, marine, and racing applications. Whether your vehicle is carbureted or fuel injected, you will find a Mallory fuel pump and regulator to feed fuel to your engine.

 

    Choosing the correct fuel pump and regulator can be complicated at times, so we have written various articles to help you make the best product decisions. This page will educate you on the styles of pressure regulators, correctly setting up pressure regulation, various fuel system designs, and choosing the correct fuel pressure regulator. Making the correct purchase will ensure optimum engine performance, consistency, and longevity. The wrong selection can be traumatic and expensive. No one likes to damage an engine or lose a race.

 

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   One of the biggest restrictions in most fuel systems is the "dead head' regulator. Dead head regulators are popular because you do not need to install a return line. However, they are not only more restrictive but also create several other problems that can be eliminated with a return style regulator.

 

   Please note that you will find dead head style regulators on most all extremely high power race only applications such as NHRA Pro Stock cars. This is because they are 1) trying to save the most weight and keep it at the back of the vehicle; and 2) they are bypassing a huge output fuel pump right at the pump. They are still using a bypass system, just doing a different way. These engines consume so much fuel that regulator is just controlling idle, return road, and launch pressures. As soon as they stage and launch the vehicle they are only concerned that the regulator is not going to be restrictive. But, other than these extreme applications, a return regulator mounted near your engine is the best configuration.

 

    Mallory offers both dead head and return style regulators. Both types are available in large and also small versions though you should never run the small regulators on pumps rated higher than 180 GPH. Dead head regulators regulate pressure by starting and stopping flow. Return regulators regulate pressure by sending excess fuel back to the tank in a continuous cycle.

    Because a dead head regulator starts and stops flow, fuel pressure between the pump at regulator is higher than the pressure between the regulator and the carb (or injectors). However, if the pressure gets too high, it can and will damage or shorten the life of the fuel pump. Therefore, the pressure coming out of the pump is limited by a device built into the pump called a bypass. On applications using a return style regulator you want the pump to run without the operation of bypass in the pump. Therefore you need to make sure that the pump you plan on using is compatible with a return style regulator. For example, the Mallory 110 GPH pump (part #4110) will not work with return style systems, but the Mallory 140 GPH pump (part #4150) will go both ways. Included with the pump is a bypass plug which you install in the pump to replace the bypass spring, allowing the pump to run wide open for use with return style regulators.

 

   Not only can the fuel pumps being used with dead head regulators fail because of pressure issues, but pumps with dead head regulators also run hotter and do not last as long as when connected to to a return-style system because it is the fuel that cools the pump. Pounding the fuel because it can not move creates more heat. Electric fuel pumps will also run quieter on a return style system.

 

   The Mallory 70 and 110 pumps are low pressure pumps that can be used without a regulator for the street or with a dead head regulator when you need to reduce the factory set bypass pressure within the pump. Mallory 140 and 250 series pumps are high pressure/high volume and must be used with a regulator (dead-head or return-style, but return style is preferred). All fuel injection pumps should only be used on return style systems.

 

    The bypass in the pump can malfunction. This can cause the pressure to drop or increase so much that the pump motor fails. Even if the bypass in the pump is working correctly, it is still possible to have a pressure drop with a dead-head regulator, even when using a large pump. See the image below:

 

 

   At idle, gauge #1 will read 10 PSI where gauge #2 will read 8 PSI. At full throttle, the increase in fuel flow will create a pressure drop between the pump and the regulator. The amount of pressure drop depends on the restriction in the fuel line ... a 4 PSI drop is not uncommon. Gauge #1 will now read 6 PSI and because a dead head regulator cannot raise the pressure, gauge #2 will also now read at 6 PSI. The result is a 2 PSI pressure drop at the carb or nitrous even though a very large pump may be in use.

 

NOTE: When using a dead head regulator, a second gauge should be installed just before the regulator. This will allow you to check that the pressure before the regulator stays higher than the set pressure.

   Most race pumps have the bypass set very high (14-25 PSI) to avoid this problem. However, this creates another problem. The higher bypass pressure makes the pump work harder and draw more amperage. In fact, the pump works just as hard at idle as it does at full throttle down the track! This is one of the main causes of early pump failure.

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   This is a profound point to be made when I (or your engine builder, carb builder, or fuel pump manufacturer) tell you to run ONLY a return-style system on your vehicles. Why would we do so? Well, if the person telling you this has your respect and has built trust with you it is easier to accept. But, the other option is that someone is just trying to sell you something and lock you into the additional costs associated with this setup. All I can tell you is that it is in your best interest to consider a return style fuel system. It is better for engine performance, track consistency, fuel pump life, and in the long run, your wallet.

 

   You can avoid headaches, especially when the pump dies just before a final-round elimination at the race track and you do not have enough time to install a new pump, or for that matter even have a spare pump to install in time to race (Loss By Default!) by running a return-style (or bypass) regulator. Here are a few benefits of a return system:

 

 

    If there is s 2 PSI pressure drop between the pump and the regulator, the return style regulator will force the pump to produce 10 PSI. If there is s 4 PSI drop, the pump will be forced to produce 12 PSI. In either case, the pressure at the regulator will remain at 8 PSI (or whatever you set it at). The pump will also live longer since it is only producing 10-12 PSI instead of 14-25 PSI.

 

   Fuel pressure regulators also suffer from something called "recovery time". Recovery time is explained as the amount of time it takes the regulator to react to changes such as a sudden increase in fuel demand (as when you jump on the throttle or hit the nitrous button). Return regulators react much quicker for several reasons. Return regulators allow the fuel to flow straight through without making a 90° turn. With a return regulator the fuel doesn't have to make it's way around the plunger like it does in a dead-head regulator. Just before you jump on the throttle (or hit the nitrous button), the fuel in a dead head system is barely moving. In a return system, the fuel is constantly moving from the rear of the car to the front and back again. This means that the fuel already has momentum, which reduces recovery time. This movement of the fuel also keeps the pump cooler and reduces vapor lock.

 

"We never race any hot tracks in the heat of summer, do we?"  (sarcasm)

 

    Dead-head regulators can also cause "creep" which means the fuel pressure tends to slowly increase. We receive numerous tech calls where a customer complains that their fuel pressure keeps climbing, or that they cannot get a stable reading (all the time). When they set the idle pressure they may not have enough pressure at or close to max RPM, or vice verse. Return regulators cannot creep, though in some cases if someone has installed the wrong size feed or return lines you will get variances in fuel pressure. 

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   Dead head regulators can only be adjusted accurately when the fuel is flowing and the engine is running. Therefore, the engine must be running to adjust the pressure accurately at the carb. The same is true for a nitrous system. Do you want to take that "guess" that the system is set properly the first time to pop the button on your nitrous system? Adjusting the regulator while the nitrous system is on is tricky at best. Return regulators can be adjusted with or without the engine or nitrous system operating. Turn on the pump and set the pressure! Simple as that ...

 

    The one thing that can make the return system operate poorly is too much restriction in the return line. To determine the restriction in the return line, turn the pump on (with the engine or nitrous off) and back the adjustment screw all the way out. Now check the pressure gauge. You should have less than 3 PSI showing on the gauge (the lower the pressure the better). If you have more than 3 PSI you must reduce the restriction in the return line. This in many cases entails free-flow fittings at the least, and in many cases a larger return line. A rule of thumb is to have at least the same size return line as your supply line.

 

    Nitrous systems are very sensitive to fuel pressure fluctuations. It is highly recommended that you run two independent fuel systems when using Nitrous (preferably with return style regulators). Two small systems with small pumps, fuel lines and regulators are usually cheaper than one large system anyway. If you must use one large system, use two dead-head regulators installed in parallel, not in series. NEVER use two regulators in series on a system with a return-style regulator! Any fuel system with a return regulator must have only one regulator on that feed line and return line.

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