The ’57 Thunderbird was the...
The ’57 Thunderbird was the debut platform for Holley’s ubiquitous 4150-series four-barrel. The rest, as they say, is history.
Henry Ford And Holley Carburetors
It was none other than Henry Ford-at the dawn of the automotive age in the in early 1900s-who encouraged the Pennsylvania-based brothers George and Earl Holley to get into the carburetor business. The two had been tinkerers and built their own automobile, but as Ford's business began to grow, the brothers wisely followed his advice and established their landmark fuel systems company in 1903 and relocated to the Detroit area.
As the auto industry grew, so did Holley. The company's carburetors mixed air and fuel for just about everything on four wheels. Of course, their iconic four-barrel carburetor was a mainstay of the muscle car era and remains a core performance component more than four decades later.
10 The fast idle adjustment...
10 The fast idle adjustment arm lowers into adjustment position when the throttle is held wide open. It has a screw head on the bottom (arrow), but it can be difficult to reach when the engine is installed in the car. You’ll have an easier time with a ¼-inch box-end wrench. Turn the screw clockwise to increase the idle speed and counter-clockwise to reduce it.
The classic Holley 4150-series four-barrel made its first appearance on the '57 Ford Thunderbird. Its use in Detroit's factory supercars mushroomed and it became a popular aftermarket product. The company was sold to Ohio-based Colt Industries in 1968 (the same year the larger, "Dominator"-series carb arrived, designed for NASCAR racing), remaining part of that company until its sale to a private equity firm in 1998. New cars were fuel-injected, so manufacturers' needs for carburetors dried up. Holley necessarily shifted its focus to aftermarket performance, but that was tough, too, as enthusiasts embraced fuel injection. In 2008, Holley filed for bankruptcy and emerged from it in 2010.
Regardless of the ups and downs of the past century, it was the urging of ol' Henry himself that helped make Holley a performance icon.
11 The first step when it...
11 The first step when it comes to adjusting the fuel level in the fuel bowl is the removal of the sight plug, which simply unscrews from the outside of the bowl. When it is removed, fuel may spill out of the hole, so be prepared with rags around the base of the carb.
12 After the sight plug is...
12 After the sight plug is removed, the fuel level in the bowl is adjusted by turning the nut on the end of the fuel bowl. Every “flat” corner of the nut is equal to 1⁄32-inch difference in the fuel level, so a 1⁄6-turn delivers a 1⁄32-inch reduction or increase in the fuel level. A matching adjustment should be made to the opposite fuel bowl. (The screwdriver is used to hold the attachment screw in place when turning the nut.)
13 The mixture screws for...
13 The mixture screws for ensuring the right ratio of fuel to air are located on both sides of the metering block. Adjustments are made in quarter-turn increments, per the instructions outlined in the main text of this story. Each turn of a screw must be matched to the complementing screw on the other side of the metering block. With a vacuum-secondary carb, these adjustments are only required on the primary side, while double-pumper carbs require the adjustments on the front and rear metering blocks.
14 Bogging or hesitation...
14 Bogging or hesitation can be due to an improperly-tensioned secondary spring, requiring a heavier spring if the secondaries open or “come in” too quickly, or a lighter spring if wide-open throttle performance seems sluggish. The spring is visible as the cap on the secondary diaphragm is removed. It simply pulls off the cap for replacement.
15 Curing stumbling upon...
15 Curing stumbling upon takeoff is possible with adjustment of the spring-loaded accelerator pump arm. Following the instructions outlined in the main text’s Number 11 tip, hold the bottom of the pump arm with a wrench and make the adjustments on the top nut with a 3⁄8-inch wrench.
16 Gaskets for the metering...
16 Gaskets for the metering block and fuel bowl are prone to deterioration and drying over time. If you’re installing an older carb on your new or rebuilt engine, it’s worth the few minutes to replace the gaskets to ensure a smooth idle and prevent leaks on your shiny, new intake manifold.