Paxton Centrifugal Supercharger - "Suddenly, It’s 1966 Again - But Better"

Paxton Centrifugal Supercharger - "Suddenly, It’s 1966 Again - But Better"

Text and Photos are Originally from Mustang Illustrated November 1998 edition

One of the most sought after Mustangs ever produced would unquestionably be the 1965 and 1966 Shelby GT350s, and one of the rarest and most valuable speed options available for them was the Paxton centrifugal supercharger kit. Coined the Cobra Supercharger option, the Paxton compressor carried a $670 list price in 1966, and could easily boost the Shelby-modified K-code small-blocks powering these rare fastbacks by close to 100 horsepower.

To better understand the dramatic power increase and what it means in the real world, consider this. To achieve the same 100 horsepower gain in 1966, a K-code 289 small-block Ford would need to be fitted with a tricked-out carburetor, high rise aluminum intake manifold, heavily ported cast iron cylinder heads, a very rowdy camshaft, and free-flowing exhaust system. The funding expended to acquire all these hard parts easily eclipses a Paxton’s price tag, not to mention the man hours necessary to install and tune such a combination. When viewed in this light, the Paxton option is a very viable alternative.

The original Paxton Supercharger kits consisted of the company’s SN-60 planetary ball-drive compressor housing pullied to produce approximately 5 pounds of boost, a specially machined sealed carburetor enclosure, custom air filter element, supercharger mounting brackets and pulleys, and a larger mechanical fuel pump. The compressor was a three-piece unit that utilized a unique internal step-up drive with a 4:1 ratio, which allowed the impeller to reach speeds as high as 30,000 rpm, while the housing was fitted with its own self-contained oiling system to keep the ball bearing surfaces lubricated.

Though a well-designed system, in itself, the early Paxton Supercharger systems still had room for improvement. The internal step-up ball-drive design limited the amount of total boost that could be run safely, and exceeding those limits, more often than not, caused the steel balls to slip and skid, galling the supercharger’s internal race.

Paxton’s new Novi G.S.S. Supercharger Kit for 1965-70 289/302-equipped Mustangs has bridged this gap with its upgraded design. The compressor housing now consists of a two-piece unit, and a one-piece solid impeller shaft has replaced the previous straight cut version. The ball bearings themselves are now located inside the housing, and the casting lends increased support to the ball-drive unit for added longevity.

"It’s the same basic concept that has been in use for over 20 years," said Paxton Products’ Bob Wyman. "Though we have been constantly upgrading and improving the design."

The Novi G.S.S., part number 1000300, is shipped with a 5-pound pulley in place on its one-piece impeller shaft, good enough to produce 850 cfm worth of airflow on a stock or mildly modified K-code 289. Should one desire more power than the stand 5-pound. Novi provides, Paxton offers a special modified impeller that can channel upwards of 1,100 cfm of airflow at slightly over 7 psi. The Novi G.S.S. kit also incorporates its predecessor’s cast aluminum one-piece mounting bracket and cast crank pulley. In addition, oiling and lubrication concerns have been addressed with the company’s synthetic Paxta-Trac fluid.

After reviewing the new Novi G.S.S.’s strong suits, we were just itching to witness its performance on an early Mustang first hand. To that end, it was off to Huntington Beach’s Wheeler’s Speed Shop, where Rich Fabbri’s 1966 Mustang fastback was about to make the transformation from natural aspiration to forced induction. The fastback sports a Wheeler-built 289 cubic inch small block topped off with reworked factory cylinder heads, a mild Competition Cams hydraulic camshaft, and Hedman headers. Before the installation began, however, Wheeler’s Speed Shop’s Glenn Gruettke motored the fastback over to nearby Jones Electronic Technologies for a quick session on the rollers of their Dynojet chassis dyno to establish a baseline.

The healthy 289 small block responded with a 318 horsepower pull in naturally aspirated form, but that reading was just an appetizer when compared to the things to come! When the dust had finally settled, the Paxton huffed Mustang had registered 447 horsepower at the rear wheels with just 6 pounds of boost pressurizing the intake manifold. That’s an astounding 129 horsepower increase at the rear wheels with no adverse effects on the fastback’s streetability, whatsoever. (WOW - a 40% increase, and I never believed the Paxton ads that said 40% - was I wrong!! - Fletch)

Paxton Centrifugal Supercharger Images

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