Reality or Myth ?

You have probably heard the unique sound of Paxton supercharger. The distinct sound it makes is more like a jet aircraft than an automobile. In addition to the cool sound, you get increased horsepower (advertised at + 45%). So, could you buy a 1968 Shelby with a factory installed Paxton supercharger ?

There is no doubt Paxton superchargers were installed on Shelbys. You don't have to look too hard to find 1966 and 1967 Shelbys with factory superchargers. During 1967, several cars were built and delivered to dealers with Paxtons installed. During 1967 "Little Red" also made its rounds. That car was a factory engineering car with a supercharged 427 engine. So, at least one big block supercharger was built.

All these cars are well documented and there is factory paperwork supporting these vehicles. In the fall of 1967, Shelby planned to install Paxton superchargers on 1968 GT350s. The Shelby unique parts catalog shows some engineering drawings of the console gauge installation. Along with the gauges, I have seen part numbers for special stripes on supercharged cars. The difference is no factory paperwork has ever been discovered to support the 1968 supercharged cars. Dealer invoices and factory paperwork would have indicated these items. Most 1968 Shelbys have dealer invoices available and all cars have some type of paperwork available today. The addition of a factory supercharger also would have altered the vehicle's drivetrain warranty.

The Shelby "over the counter" parts catalog does list the supercharger as a $435.00 option (w/o gauges). To put that in perspective, that is approximately 1/10 the cost of the new car. On a new Mustang, something like $3,000 in today's money. The expensive made it unlikely that very many dealers actually added the superchargers, especially when big block cars were easily within reach of most buyers.

So, you are probably thinking big block blower cars are out of the question? Sort of. At least two big block factory engineering cars were built during 1968. It is unlikely these vehicles were sold to the public with the superchargers intact. It was common for Shelby to pull production vehicles and use them for experimentation. Such things as fuel injection, radios and different axles were tested. When finished the cars were returned to stock specs and sold.

8T03S110576-00056, Was one of the first four cars built. It was the first regular production Shelby convertible and the first 1968 big block car. It was also a factory engineering vehicle used to test the 428 Cobra Jet engine and the Paxton supercharger. The car is currently under restoration and will be restored with the supercharged 428 Cobra Jet motor. The car appears on a list of factory engineering cars assigned to Shelby. A copy of this list is maintained by the Shelby American Automobile Club.

8T02R215872-04102 Was a yellow GT500 KR fastback. This car was also used by the engineering department to test the supercharged 428 CJ. This car is in a private collection. Curt Vogt of Cobra Automotive built a supercharger system for the car.

As you can imagine engineering a supercharger system on a big block engine presents some unique challenges. The physical size of the engine is one big obstacle.

Let's take a quick look at a couple of the prominent Paxton components: air boxes, blowers and gauges.

At least three different carburetor air boxes were around in 1968. The first and most common is the "PAXTON" lettered box. It probably wasn't used on Shelbys. Many Shelbys used the "COBRA" lettered box. During 1968, Shelby stopped using the trademark "Cobra" and returned it to Ford. The third type of air box is the "SHELBY" lettered air box. The SHELBY lettered box is probably the rarest of the three and most likely replaced the COBRA air boxes.

Blowers came in three colors. The black painted factory blowers were common on early Shelbys. Later cars probably used a blue painted blower. White blowers were sold over the counter and used on later cars. Most blowers have a serial number and a date code. This was because they had a separate warranty.

1966 and 1967 Shelbys do not have consoles. Gauges were mounted under the dash. Most people agree these gauges were made by US gauge company specifically for Paxton applications. The gauges have a black face. Today, these gauges command a healthy price and out of reach for all but the most exacting restorations. It appears there was a second set of gauges planned for 1968 Shelbys. These gauges were made by Stewart Warner. I do not have much more information on them, but they were designed to be added to the Shelby consoles.

This picture shows the US/Paxton gauges in a 1968 console.

If just want to have fun and find a car that sounds as cool as it looks, the supercharger is a neat addition. If you have any information that contradicts this article I would enjoy looking it over.

I would like to thanks Craig Conley of Paradise Wheels (the blower king) and Curt Vogt of Cobra Automotive for their contributions to this article.

If one blower is not enough, how about two?

You can read more about the restoration of the factory engineering car # 56 in future articles.