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Street Race Truck More... The Toolbox

How to Install Fuel Pressure Regulators for Carburetors

12/20/2019
Fuel Pressure Regulators For Carbs With Electric Pumps

Choosing the correct Fuel pressure regulator won’t raise your blood pressure, if you know what to look for!

When choosing a fuel pressure regulator for your ride, you need to take into consideration several factors. The regulator is a critical piece and should to be matched to the type of fuel delivery system and the fuel pump that you are using or plan to use. This video will help explain fuel pressure regulators that were designed for use with a carburetor.

It’s always a good idea to first do a little research on your fuel pump and obtain some basic information such as, flow, maximum working pressure, even the amperage draw. If you haven’t already purchased a fuel pump we’ve created a great video that explains the various pump designs and how they work, to help you make your selection. There are plenty of fuel flow calculations you can do to help you through it, but we’ve already done the hard work for you. We suggest following our recommendations so you can correctly match a regulator to your fuel pump. Check out Holley's fuel system selection chart as a reference.

Most lever style mechanical fuel pumps don’t require a regulator and some electric fuel pumps even have the regulator built right into them, and eliminating the need to purchase an external unit. These pumps are typically low pressure units and were designed for use with carburetors only. If your fuel pump requires an external regulator, here’s what you need to know before you make your next purchase.

How To Install a Deadhead-Style Fuel Pressure Regulator

Lets start with one of the simplest yet very popular regulator set-up, it’s the deadhead-style regulator. Most carbureted engines use this style of regulator which is placed between the fuel pump and the carburetor. We offer a large selection of regulators in this design from manufactures like Holley, Quick Fuel, Earl’s and Mr. Gasket. Essentially, the deadhead style regulator uses a restriction in order to lower the fuel pressure by simply decreasing the fuel flow. This is accomplished with the use of a diaphragm and seat that restricts the fuel flow and uses a spring to provide pressure adjustability. A dead-head regulator doesn’t use a return line and therefore there is no fuel redirected back to the fuel tank. The lack of a return line helps decrease installation costs but it can also limit the performance capabilities. These regulators come in a variety of styles and typically regulate fuel pressures in the 1-9 psi range. They’re perfect for use with most low pressure mechanical as well as some electric fuel pumps. Check out our electric fuel pump vs mechanical fuel pump guide for more on key differences between the two. We also cover perks of electric fuel pumps more in depth in in this electric fuel pump advantage guide.

Whenever you increase engine power you proportionally increase fuel demand. High performance engines with higher fuel flow demands and can wreak havoc on a dead-head style regulator. Some common problems that you might encounter when over-working a dead head regulator include; fluctuating fuel pressure, pressure creep, as well as the possibility of over-powering the carbs needle and seat which can flood your engine and wash the cylinder walls. Also since there is no bypass allowing the recirculation of unused fuel, the temperature of the fuel rises, increasing the chance of vapor lock!

How to Install A Bypass Fuel Pressure Regulator

A bypass style regulator like this Holley unit can help alleviate these issues by bleeding off the excess fuel pressure and returning it directly back into your fuel tank. This design helps eliminate pressure creep, lower fuel temperatures and providing a more stable pressure curve. A bypass-regulator can also react much quicker to sudden fuel flow changes and correct a potential lean condition before it’s too late. It’s a simple swap that can usually be done in an afternoon and only requires the purchase of a few extra components to complete, but the benefits are well worth your money and your effort.

A big misconception is that Bypass regulators are only for use with fuel injection! This just isn’t true. By plumbing a by-pass regulator before the carburetor, drag racers can build higher pressure in the feed to help counteract the high g-forces that they experience during hard launches and rapid acceleration. In a street/strip application we recommend running the feed line directly to the carburetors fuel log then placing the regulator on the return line side of your fuel log. This allows the fuel to flow unrestricted to your carburetor, but still regulates the pressure and returns the unused fuel back into the gas tank.

Carbureted systems can benefit from a bypass regulator just as much if not more than an EFI system. In fact because the fuel is always circulating in the system you get a more consistent fuel supply and a reduction in fuel temperatures. It is probably one of the most effective ways to help prevent vapor lock when running a carburetor. When combined, all these factors help reduce the overall amperage that’s needed to run the fuel pump. This results in a quieter fuel pump and can increase your fuel pumps life expectancy.

Adjustable Fuel Pressure Regulators

Some regulators have a fixed pressure setting, while most aftermarket regulators are adjustable by design. Adjustable fuel pressure regulators allow the user to set the fuel pressure based on their unique combination of components and application. Some aftermarket regulators also include a circuit designed to maintain consistent fuel pressure under severe load and/or RPM. Under wide-open-throttle situations, the engine requires more fuel than it does at idle. Some regulators use a vacuum signal to "see" this additional load and provide the proper ratio needed for the conditions. This is even more important on boosted or nitrous engines that need additional fuel volume to minimize the chance of detonation.

Taking the time to plan out your fuel system and matching quality components will definitely pay off in the end. Using the best aftermarket fuel pressure regulator with your carburetor ensures a safe and reliable fuel system performance for your engine. It will result in a better running, high-performance engine. Shop the full line of high performance Holley fuel pressure regulators available at Speedway Motors.

For more expert advice on fuel systems, check out our fuel system overview and fuel system design guide.

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