Although carburetors have been long extinct in production vehicles, in the world of the automotive hobbyist, their popularity endures. When you get right down to it there are many reasons in favor of a carbed setup, from tradition and that correct “vintage” vibe, to the relatively low cost and ease of installation and tuning. The bottom line is that carbs get the job done, and if correctly set up and tuned, perform very well. A four-barrel carb will get you on the road while requiring little more than winding in four bolts and connecting the fuel line and linkage to be ready to run.
Enthusiasts have more choices in carburetors today than ever before. At the low-buck end, some choose to bottom feed using cast-off OEM or used-up swap meet pieces, working mechanical magic to make them viable. For others, the game plan revolves around opening the box on a brand-new unit, and getting up and running with minimal hassle. Today’s aftermarket is chock-full of high-end monster-sized race-style carburetors that would have been hard to imagine just a few short decades ago. While these mixers have their place, a true driver street application benefits from a carb designed for just that application.
We took a detailed look at five new budget carburetors, all aimed at the street user. These carbs are all built with street calibrations, they come with a choke and vacuum or air-valve–regulated secondary operation, and are offered in sizing to meet the needs of moderate street engines. The features and configurations of the carbs vary, but the general theme running across the group is reliable and efficient street operation and value for the dollar.
Aluminum Street Avenger
Holley’s series of Street Avenger carbs have developed a following with performance enthusiasts since the original carbs were introduced nearly a decade ago. The idea was to provide a truly street-friendly version of Holley’s race-proven modular carb design. The emphasis in the Street Avenger line is making the carbs as reliable and goof-proof as possible, with enhanced street metering calibrations, while retaining the familiar tuning aspects that have made Holley famous. The latest of these carbs are the Aluminum Street Avengers, available in 570-, 670-, and 770-cfm ratings to suit most street applications. Owing to their aluminum construction, these carbs are substantially lighter than their traditional cast-zinc counterparts, saving about five pounds, and the aluminum holds its polished finish much longer for lasting good looks.
These carbs have a vacuum-secondary configuration, and come equipped with Holley’s quick-change vacuum diaphragm, allowing quick and easy secondary diaphragm spring changes for rapid recalibration of the secondary opening rate. The large sight glass and center-hung floats make float level calibration a simple process. Four-corner idle adjustment provides superior idle control with idle circuits built into both the primary and secondary sides of the carburetor, a feature normally found on higher-end or race units. To accommodate a variety of street installations, the carbs are equipped with a full complement of vacuum fittings, including PCV, brake booster, ported vacuum advance, and a manifold vacuum accessory port. If you are looking for a street-orientated carb in a familiar and traditional Holley configuration, the new Aluminum Street Avengers are right on target.
By the Numbers
Holley Aluminum Street Avenger
Rated Flow: 570, 670, 770 cfm
Secondary Type: Vacuum secondary with quick-change diaphragm
Mounting Flange: 4150/squarebore
Choke: Electric or manual
Fuel Metering: Primary and secondary metering block, primary power valve
Options: Accepts most Holley accesories
Special Features: Straight boosters, bowl sight glass, four-corner idle, blow-proof power valve, lightweight aluminum body
Street Price: From $359
The Aluminum Street Avenger comes with dual metering blocks, center-hung bowls, and four-c
These Holley carbs come through with straight-leg boosters in the primary and secondary ba
Stripped down, we can see the Aluminum Street Avenger comes with the power valve enrichmen
Quick Fuel has attacked the street carb market with a vengeance with this pair of carburet
Quick Fuel Slayer
Looking for high-end carb features in a modestly priced street carb? The new Slayer Series carbs from Quick Fuel are as big on features as they are low in price. Configured as a traditional modular carb, these units are familiar to most performance enthusiasts, using well-known tuning techniques. Designed for street duty, the Slayer Series carbs feature vacuum-secondary actuation, with Quick Fuel’s innovative Quick-Set adjustment feature. The opening rate of the secondary butterflies is adjusted by a simple turn of a screw—it doesn’t get any quicker or easier than that. The secondary side of these carburetors does not come with a metering block, however, they come with the next best thing: Quick Fuel’s metering plate with replaceable jets. Working in tandem with the metering plates is a notched float, which allows the compact secondary arrangement internal clearance, even with jet extensions.
For a budget street carb, the Slayer is packed with features that are normally found on higher-end or race carburetors. The idle and high-speed air bleeds are a screw-in configuration, making them fully tunable. Similarly, the key tuning points of the power valve channel restriction and idle feed restriction is that they screw in, and are replaceable. This level of calibration potential is not normally seen in a budget-minded street carburetor. Add in the advantage of low-restriction downleg boosters at all four corners, large float bowl sight glasses, and polished aluminum construction, and the Slayer certainly has the features to make them worthy for any high-performance street application.
By the Numbers
Quick Fuel Slayer
Rated Flow: 600, 750 cfm
Secondary Type: Vacuum secondary with quick-set diaphragm
Mounting Flange: 4150/squarebore
Fuel Metering: Primary metering block, secondary metering plate with replaceable jets, primary power valve
Options: Ford throttle linkage, single-feed supply with transfer tube
Special Features: downleg bossters, bowl sight glass, lightweight aluminum body, replaceable air bleeds, power valve channel restrictions, and idle feed restrictions
Street Price: $299
Slayer carbs come with Quick Fuel’s outstanding Quick-Set secondary diaphragm adjustment s
Not normally seen on a budget-minded carb, the Slayer comes through with efficient downleg
The secondary side of the Slayer economizes the package with a secondary metering plate in
Street Demon 625
Of our feature carburetors, the all-new Street Demon 625 carbs stand out as a unique offering in the street carburetor marketplace. Reminiscent of the Carter Thermoquad, the Street Demon is actually a clean-sheet design that incorporates its own unique configuration, while taking advantage of some of the best features of proven carburetor designs. The carb’s basic configuration uses small 1⅜-inch primary throttle bores for high air speed and quick throttle response, as well as the potential for improved fuel efficiency. The small primary is augmented by a dual-booster venturi arrangement, working in conjunction with the conventional main venturi in a setup dubbed “triple stacked boosters.” The upshot is a very responsive primary circuit, with a substantially improved metering signal. Primary fuel enrichment is catered to via a pair of independent spring-loaded primary metering rods working with a unique primary jet.
On the secondary side, the carb takes a different approach to the large throttle bores of an OEM spreadbore. Rather than using oversized round throttle plates, the carb features a large single “goggle” valve, which greatly increases the flow area compared to a pair of individual round throttles. This configuration allows the carb to be designed in a more compact throttle configuration for its flow capacity, allowing it to retain compatibility with a standard 4150 square-bore flange intake manifold. The dual-pattern baseplate of the Street Demon also allows it to directly bolt onto a spreadbore intake manifold.
The secondary does away with the restriction of a conventional venturi or boosters, instead taking advantage of the pressure drop across the adjustable contoured air valve to draw fuel via the pair of secondary discharge nozzles. Metering to the secondary main circuit is controlled by conventional Holley jets, making tuning simple. The opening rate of the secondary air door is controlled by adjusting the tension on the torsion spring, and can be accomplished quickly without the need for special tools.
The carb is available in full aluminum construction, optionally polished, or with a modern phenolic resin body, which is said to maintain a fuel temperature approximately 20 degrees cooler than an all-metal carb. These Street Demon carbs are aimed directly at the true street machine, with reliability, responsive performance, efficiency, and ease of use being the primary goals. We can’t wait to try it.
By the Numbers
Street Demon 625
Rated Flow: 625 cfm
Secondary Type: Air valve/goggle valve secondary throttle plate
Mounting Flange: Universal 4150/spreadbore
Fuel Metering: Primary jets and metering rods, secondary jets
Options: Polished aluminum or phenolic body; TPS; A/C idle Solenoid
Special Features: Triple stacked primary boosters, single fuel inlet. dual-pattern baseplate
Street Price: $349 (all aluminum); $379 (polymer bowl); $439 (hand polished)
Small 1⅜-inch primaries are augmented by a one-of-a-kind “goggle valve” high-capacity seco
Fuel delivery in the primary is enhanced by the dual boosters working with the conventiona
Most of the working hardware is housed in the air horn assembly, including the plunger-typ