In the 1950s, thousands of production cars and countless hot rods were equipped with McCulloch centrifugal superchargers. Let’s take a closer look at how these unique devices work. 

 

The McCulloch of McCulloch superchargers was Robert Paxton McCulloch (1911-1977). A Stanford-trained engineer, he received a large inheritance from his maternal grandfather, John I. Beggs, an electric utility tycoon and business associate of Thomas Edison. Assembling a team of engineering talent, in 1937 he formed the McCulloch Engineering Co. in his native Milwaukee.

 

Among McCulloch’s first products was a centrifugal supercharger for the Ford V8 that was similar to the production blowers then offered by Auburn and Graham, but belt-driven for simplicity and ease of installation. In 1943, the company, then mainly engaged in defense work, was sold to Borg-Warner for $1 million and McCulloch moved to Southern California to start another company

Products of the new McCulloch Motors Corporation included two-stroke drone engines and a successful line of chain saws. In 1952, McCulloch reentered the supercharger business with an entirely new type of centrifugal blower, first offered in the aftermarket, and then adopted on a production car by Kaiser in 1954: the VS57. The U.S. car market was increasingly dominated by overhead-valve V8s, and with no V8 in its portfolio, Kaiser added supercharging to its six-cylinder products in an attempt to remain competitive.

 

Standard equipment on the deluxe Kaiser Manhattan, the McCulloch belt-drive blower (above) was paired with the automaker’s aging L-head six, which displaced 226 cubic inches and in standard form produced 118 hp at 3,650 rpm and 200 lb-ft at 1800 rpm. With a modest 4 psi of boost, the supercharged version was good for 140 hp at 3,900 rpm and 215 lb-ft at 2,400 rpm, broadening the torque curve significantly. This was achieved with the normal  compression ratio of 7.3:1, while a standard-type carburetor was housed within an airbox to eliminate pressure differentials. It was a simple and straightforward installation. The magic, if you will, was inside the McCulloch blower.

 

On the VS57, the VS stood for Variable Speed while 57 was possibly shorthand for the unit’s minimum drive ratio, 5.7 times crank speed. To eliminate gear noise and torsional vibration, two traditional trouble spots with centrifugal blowers, the turbine speed was multiplied not by a gearset but by a spring-tensioned friction ball drive with a fixed ratio of 4.4:1. The blower had its own oil system and pump independent of the engine using Type 1 automatic transmission fluid.

Here’s the variable-speed part: Under the big emblem on top of the blower was an electric solenoid operated by a throttle kick-down switch. This enabled an air-pressure governor mechanism to move the inner sheave of the blower’s V-belt pulley in and out, adjusting the pulley’s effective diameter and thus its drive ratio, controlling the blower’s output. A spring-loaded idler pulley balanced the forces and took up the belt slack.

 

In what McCulloch called the “Low Blower” position with the pulley fully closed, the effective ratio was 1.3:1, for a combined blower drive ratio of 5.7:1. In the “High Blower” position with the pulley fully open, the ratio was 2.3:1 and 10:1 total. At steady highway cruise or “Low Blower,” the boost was approximately 1.5 psi. Maximum boost at “High Blower” was limited to 5 psi by the pressure-operated regulator and the unit’s internal design, all of which were engineered to keep the impeller speed under 30,000 rpm. From the start, McCulloch had targeted the VS57 for road performance and reliability rather than maximum horsepower.

In the Kaiser system, boost was conservatively limited to 4 psi, and while the blower significantly improved the performance of the old Continental-based L-head six, they were no match for a modern OHV V8. Willys Motors (Kaiser-Frazer’s corporate name after 1953) built around 5,000 supercharged Kaiser Manhattans before retiring from the U.S. passenger car market at the end of the 1955 model year.

 

While Kaiser dropped the McCulloch blower when it left the car market, Studebaker-Packard picked it up in 1957, where it was standard on the Studebaker Golden Hawk in 1957-58 and on all Packards in 1957. As adapted to Studebaker’s 289 CID V8, the S-P system (above) was much like the Kaiser setup with a pressure box for the carburetor and a V-belt drive with tensioned idler pulley. With 275 hp at 4,800 rpm (.95 hp per CID, note) and 333 lb-ft of torque at 3,200 rpm, the supercharged Golden Hawk was declared one of the hottest U.S. cars on the road in 1957.

As McCulloch’s automotive line shifted to the Paxton Products label in 1956-57, taking Robert McCulloch’s middle name, supercharger production continued with improved versions of the VS57. In 1957, Ford adopted a different Paxton blower design, the VR57 (below left; fixed pulley and variable-ratio ball drive) for its Phase 1 and F-code models rated at 300 hp.

When Andy, Joe, and Vince Granatelli acquired Paxton in 1958, they developed the simplified SN60 supercharger with a fixed drive ratio (shown with Andy, below right) and ultimately the company was purchased by Studebaker, which offered Paxton blowers on all models in 1963. The Paxton name is still alive today under multiple ownerships, producing blowers for automotive and industrial use.