Remove the old carb and replace it with the new Edelbrock VRS-4150. This is a straightforward swap and well worth the effort.
By Ryan Manson – Photography & Videography By Ryan Foss Productions
While the popularity of EFI has grown exponentially in recent years as kits became more affordable, technology more advanced, and tuning abilities more user-friendly, it’s hard to imagine that a company with such a pedigree as Edelbrock would turn its attention back to the past with a completely redesigned four-barrel carburetor. But that’s exactly what they did with their new line of VRS-4150 race and performance carburetors. The argument for upgrading to EFI has been beaten to death, and there’s no denying its value in today’s hobby, but for all-out performance and ease of tunability, it’s hard to argue against the tried-and-true traditional carb. And for those of us who might be racing in a class where one is required, a better carburetor will always be well received.
Edelbrock’s latest carb offering, the VRS-4150, offers many of the same features and functions that their tried-and-true AFB carb line has provided in the past, with a focus on street performance and race car applications. Available in cfm ratings from 650-950 cfm, the VRS-4150 is an extremely versatile and highly capable carburetor with an impressive tuning range.
Edelbrock’s experience with carburetors dates back to the very first Flathead that Vic Sr. and his team tuned on the company’s dyno. By the early 1970s Edelbrock not only sold Holley carburetors but also offered an on-site tuning service. From this experience Edelbrock created Holley upgrade kits and fully calibrated carburetors. When Colt Industries bought Holley, there was a parting of the ways and Edelbrock started working with Carter AFB carburetors. As a result, Holley started making intake manifolds and the competition was on. Eventually Edelbrock developed its own AFB-style carburetor with Magneti Marelli. This simple carb design has been installed on thousands of hot rods, muscle cars, street machines, and classic trucks over the years, filling a significant gap in ready-to-run carburetors. However, Edelbrock realized that while the Performer carb served that niche, there was another group still looking for a solution—the race and street performance enthusiasts. That’s where the VRS-4150 comes in.
Both the primary and secondary float bowls come equipped with a pair of 7/8-20-inch threaded inlets, fitted with AN-6 fittings from the factory. Only one side per float bowl is required, with the opposite side plugged. Fuel enters the float bowl through these fittings, metered by the adjustable needle and seat, set via the float level adjustment window. Proper float height is typically half the height of the window and comes preset from the factory.
Designed from the ground up, the VRS-4150 is a street-friendly carb with race-ready features. Nearly every aspect of the carb is adjustable, either with a simple turn of a screw or by replacing a jet or air bleed, making it highly versatile for changes in atmospheric or altitude conditions. But don’t be fooled by all the bells and whistles; Edelbrock designed the VRS-4150 as a ready-to-run carb for mild street cars as well, with settings calibrated from the factory to perform well in most real-world scenarios.
As the fuel enters the float bowl, a cast-in shape commonly referred to as the “mustache” directs the fuel to run down the sidewalls to prevent foaming of the fuel. Additional cast-in baffles minimize sloshing and when combined with the corner chamfers of the float, they prevent the needle and seat from closing during hard cornering.
When it came to designing a new performance carb, Edelbrock chose not to reinvent the “wheel.” Instead, they based their new offering on the classic 4150-style carburetor design, which dates back to the late 1950s. Used in many Ford vehicles of that era, the 4150-type carb proved popular among enthusiasts seeking to achieve big V-8 power with ease of tuning. Edelbrock took that basic design and refined it, introducing several improvements and tweaks along the way. Taking a closer look at the VRS-4150 will reveal those changes and show the carburetor’s capabilities, making it a great option, whether you’re cruising around town, ripping through an autocross course, or spinning those slicks down the dragstrip, Edelbrock offers a VRS-4150 carburetor to meet your needs.
From the float bowl, fuel enters a billet aluminum metering block through either the main jets, the intermediate feeds, the power valve circuit, or the auxiliary idle feeds if used. Here, the two main or high-speed jets are mounted on the jet extender tubes. The extended length of these jets puts them further into the float bowl, another feature designed into the VRS-4150 to prevent fuel starvation during aggressive acceleration. Flanking the main jets are the intermediate circuits, while the idle feed restrictors are further out and slightly higher, almost even with the idle mixture adjustment screws on the sides of the metering block. Just above and in the middle of the main jets is a vacuum-operated power valve. This function operates during low-vacuum (high-throttle input) regimes, adding additional fuel.
This clear metering block models the paths of the fuel and air as they are combined and fed into the main carburetor body.The VRS-4150 features four fueling circuits per venturi; single idle and intermediate circuits and two high-speed circuits, all of which are fully adjustable via replaceable bleed jets, located in the main carburetor body. Changing the size of these bleeds effectively adds more or less air to emulsify the fuel in each respective fueling circuit.The 650-cfm carb features downleg boosters for fuel delivery due to space limitations caused by the smaller venturi size (1-1/4 inches) based on various motorsports regulations. These work great on smaller displacement, street-based applications due to their simplicity and reliable fuel delivery.The larger venturi sizes on the 750-, 850-, and 950-cfm carbs, however, allow for the use of larger annular boosters, which help deliver a more precise signal to the fuel system thanks to their unique design. Annular boosters respond very well to low vacuum, making them an ideal design for high-performance street and racing applications.Here you can see the accelerator pump well; 650 & 750 cfm models get two 30cc capacity wells, and the 850 and 950 cfm models use 50cc wells. Multiple vacuum ports provide ported and non-ported vacuum signals for vacuum advance timing control, brake boosters, and more.During normal idle operation, the low-speed transfer slot in each venturi is only slightly uncovered by the butterfly (adjusted via the throttle blade position adjuster and preset from the factory), metering the exact amount of air and fuel needed by the engine to maintain the desired idle rpm. As throttle inputs increase, the transfer slot is further exposed, allowing more fuel and air through the idle circuits until the transfer slot is fully uncovered and the carburetor is in an off-idle state. Further opening of the throttle uncovers the intermediate circuit tube that supplies fuel as the carburetor transitions to the main circuit. As throttle commands become more aggressive, the main metering circuits activate, delivering fuel and air through the boosters.Initial idle mixture adjustments are made using the four-corner idle mixture adjustment screws. These come preset from the factory at 1-1/4 turns out, which we found to be a solid baseline setting.The idle speed adjustment screw allows for setting the idle speed without altering the throttle blade position and is another adjustment to make during initial installation. The throttle blade position adjuster screw also influences idle settings by opening or closing the throttle blades, with the optimal setting having the transfer slot in the venturi only slightly uncovered. Also note the adjusting nut for the accelerator pump located at the far left and the cover for the optional installation of a throttle position sensor, which is often required by electronic overdrive transmissions.The VRS-4150 features a moderate primary-to-secondary link that allows the carb to work like a traditional mechanical secondary carb. Edelbrock also offers links for a more aggressive secondary link as well as a 1:1 link that enables the carb to operate both primary and secondary sides simultaneously. The linkage arm on the VRS-4150 offers various attachment points for different throttle applications, as well as transmission kickdown or TV cables.Using the same bolt pattern and flange design as all 4150 and 4500 carburetors, the VRS-4150 fits a wide range of intake manifolds and applications. For our 302-powered 1932 Ford, we chose Edelbrock’s Performer Intake Manifold in Chrome Plasma Finish (PN 2121-CP) because we wanted a look that was great and torque that performed well from idle to 5,500 rpm.Because of the Performer’s low profile and dual-plane design, we needed to add a spacer to the intake flange for clearance of our fuel log. The Performer’s dual manifold design separates the plenum and works best with a four-hole spacer to ensure each cylinder’s signal is metered by only two barrels of the carburetor at a time. The spacer also provides thermal insulation between the intake manifold and the carb.In contrast, this open plenum spacer is better suited for a single-plane intake manifold, where each cylinder draws signal from the entire carburetor.Installing the VRS-4150 carburetor is similar to installing most other four-barrel carbs and still allows compatibility with most cable mounting bracket systems.To feed the dual 7/8-20-inch inlets, we chose Edelbrock’s Adjustable Fuel Log (PN 8100). This provided a plug-and-play solution since our 1932 already had an AN -6 fuel line in the correct location. With the installation complete and the 302 roaring to life, a few minor adjustments to the four corner mixture screws and the idle speed screws were made before a quick trip around the block. With the installation complete and the 302 roaring to life, a few minor adjustments to the four corner mixture screws and the idle speed screws were made before a quick trip around the block.The initial performance of the VRS-4150 was impressive, to say the least, and the out-of-box settings were very close to ideal. With the carb nearly dialed in right out of the box, we finished it off with a polished Edelbrock Elite II Series air cleaner (PN 4273) and a pair of matching Elite II valve covers (PN 4264) with matching push-in breathers (PN 4204).
