Holley Carburetors. Mike Mavrigian

with the bolt holes spaced farther apart from front to rear when compared to left-to-right bolt holes.

       Throttle bore diameters on 4150- and 4160-series carbs measure 1.563 to 1.688 inches, depending on specific part number.

       The throttle bore diameter on Dominator (4500-series) carbs measures 2.00 inches.

       You don’t need a tape measure to readily see the difference in throttle bore diameters. The Avenger (left) has 1.688-inch bores, while the 1050 Dominator (right) is gifted with whopping 2.00-inch bores. Bore diameters are even larger on high-volume models, with 1,475-cfm Dominators featuring 2.350-inch bores.

Baseplate Bolt Pattern

      All Holley 4-barrel carburetors (except for the 4500 series) have a baseplate bolt pattern with the baseplate-to-intake manifold bolt holes stagger-spaced 5 (left to right) × 5⅝ inches (front to rear). As previously mentioned, the 4500-series Dominator baseplate bolt pattern is unique to that series and includes a square bolt pattern measuring 5.375 × 5.375 inches. The Dominator requires the use of an intake manifold designed to accept a Dominator. However, adapters are available that allow you to mount a 4150/4160 to a Dominator manifold and vice versa. Depending on the specific intake manifold, installing a Dominator onto a manifold designed for the 4150/4160 carbs may require enlarging the manifold’s plenum ports.

      Holley Carburetor Models and Types

      Holley carburetors are available in different “series” designs. Within each family are variations in CFM, choke design, secondary design (on 4-barrel carbs), etc.

      The 4160-, 4150-, and 4500-series carburetors are, by far, the most commonly used. Depending on the engine size and application, carbs in these three series can be applied to street vehicles. However, generally speaking, the 4160 is intended for the street, the 4150 is for serious street and racing, and the 4500 is designed primarily for racing.

      For a complete listing of specific Holley carburetor models and the vehicles on which they were installed, please refer to the Appendix.

       Series 4160

      The 4160 includes a single fuel inlet with a transfer tube that feeds the vacuum-operated secondaries and a secondary metering plate rather than a secondary metering block. The metering plate is non-adjustable and has no replaceable jets. A power valve and an accelerator pump are located on the primary side only. The 4160 carburetors are the less-expensive versions of the 4150s but can be upgraded easily to 4150 status by installing a secondary bowl and metering block kit.

       Series 4150

      The 4150 carburetors are similar to 4160 carbs; their primary difference lies with secondary operation. The 4150 is enhanced with features such as dual fuel inlets, vacuum or mechanical secondary operation, metering blocks (with replaceable jets) on both the primary and secondary sides, and a power valve on both the primary and secondary sides. The 4150 series offers a much wider range of CFM sizes compared to the more “basic” 4160.

       Series 4500

      Famously known as the “Dominator” series, the 4500 is the big boy on the block. Notable differences between the 4150 series and the 4500 series are the larger 2.00-inch bores, a secondary throttle linkage that runs internally, throttle-shaft openings sealed to prevent contamination, and the elimination of an air horn/air choke to control air entry. The Dominator series has a larger bolt pattern for intake manifold mounting. Although adapters are available to mount a 4500 carb onto a 4150 intake manifold, the proper choice is a manifold that is designed to operate with a 4500-series carburetor. Dominators are good choices for engines producing more than 625 hp.

       Series 4165

      This series is known as a Double Pumper because it features mechanical secondaries, an accelerator pump at both bowls, and a metering block with jets at both primary and secondary sides. It has a square bore pattern.

       Series 4175

      These carburetors have a spread-bore base and are designed as a direct replacement for the GM Quadrajet. Series 4175 carbs have electric chokes and a single fuel inlet.

       Series 4010

      These carbs have a square bore with either mechanical or vacuum secondaries.

       Series 4011

      This series is essentially the same as a 4010, but is designed for spread-bore intake manifolds. It is offered with either mechanical or vacuum secondary operation.

       Series 4224

      Built as a 660-cfm drag racing carb, this carb has a center-squirter design that squirts fuel into all four barrels at the same time, aided by a hefty 50-cc accelerator pump.

       The 4150 and 4160 bolt spacing, from front to rear measures 5⅝ inches.

       Dominator bolt spacing, from left to right, is specified at 5⅝ inches.

       Dominator bolt spacing, from front to rear, is specified at 5⅝ inches.

Air-Cleaner Base

      The 4150/4160 series requires a 5⅛-inch air cleaner/gasket; the larger Dominator requires a 7-inch air cleaner and gasket. These are the standardized published sizes that appear in all catalogs; they provide a comfortable drop-on fit. Actually, the 4150/4160 carb air cleaner inside-diameter gasket surface measures approximately 5.001 inches; the inside-diameter gasket surface of the Dominator measures approximately 7.251 inches.

       Air Cleaner Threads

      Most Holley carbs, including the 4150/4160 series, have a 1/4-20 threaded center hole to accept an air cleaner stud. The Dominator (4500) series has a larger 5/16-18 threaded hole. Inexpensive male/female adapters are readily available from any performance retailer to allow the use of either stud size. Adapters are available with 1/4-20 male thread and 5/16-18 female thread as well as 5/16-18 male thread and 1/4-20 female thread.

       CHAPTER 2

       HOLLEY CARBURETOR OPERATION

      Holley 4-barrel carburetors are dual-stage, downdraft