The Mule: 1969 Twin-Turbo Camaro That Redefined American Muscle

Modern muscle cars, such as the Mustang and Camaro, have been sporting turbochargers affixed to four-cylinder engines in recent years, And unlike some failed attempts in the mid-70s and 80s, it seems American automakers have gotten it right, as the turbo option is one of the most popular selling configurations for each model. 

While we cannot definitely say this custom twin-turbo 1969 Chevrolet Camaro built by Mark Stielow, manager of Program Engineering for General Motors, helped Chevrolet embrace and redefine American muscle cars. We can say the Mule has helped spark the Pro Touring craze and that Stielow is one of the most respected Pro Touring builders in the industry.

What’s In A Name?

When the Mule made its debut Stielow was quoted by Block Performance saying “at GM when [they] have a development property, [they] typically call it a ‘Mule’ property. So, it was supposed to be a test vehicle for a bunch of ideas [he] had.”

It has been confirmed the car has been studied by other GM engineers in the design studio while they worked on designing the new Camaro.

The term “Pro Touring,” is another one of Stielow’s creations. It refers to a style of classic muscle car with an enhanced suspension, brakes, and drivetrain, but that mostly retains its original external appearance.

Photography courtesy of the Audrain Automobile Museum

The Icon Is Born

Many of the customizations to the Camaro are not visible on a first glance, hence pro touring. The entire body of the car is fitted with a discreet roll cage that is seen in the engine compartment, behind the front seats, and all the way back to the trunk. Embracing factory lines, the cars exterior is mostly stock but with closer inspection the hood has been customized to make space for the massive air intakes below.

In 2001, during the build of The Mule, most cars had a leaf-spring and solid-axle combination for their suspension. Stielow created a rear suspension with a four-link axle with coil-over springs for better shock absorbency and overall handling. The biggest difference between the two is that not only does the coil-over system disperse the workload better, but it is also adjustable for a harder or softer ride.

With Pro Touring in mind, an Art Rasmussen subframe reworked by Stielow with power rack-and-pinion steering and a Currie aluminum 9-inch rear.

Under The Hood

The most impressive part about this car is its engine- it is designed to either take to the store or take to the track without drawing too much attention. It is powered by a custom twin turbo 389cid aluminum small block Chevy rated with 1,021hp on an engine dyno. To manage those big horsepower numbers the build features electronic fuel injection, adjustable boost knob to allow you to run on any octane gas, a reworked six-speed Viper transmission, and four-wheel disc brakes.

There are custom-made elements throughout the engine compartment that reflect his incredible craftsmanship and engineering background. Tucked away are custom-made aluminum shields protect the roll cage and the cool-air intake from heat from the neighboring twin-turbos and headers. Stielow also custom-made all of the brackets found throughout the engine compartment.

Echoing the factory aesthetics theme, the interior was left almost entirely stock except for the 5-point bucket seats and a custom gauge cluster for racing. There is a small light on the tachometer that turns on when the driver should upshift in a race. This is so the driver can keep their eyes on the road without harming the engine.

Build Specs:

  • Configuration: Custom twin-turbo-boosted front engine
  • Engine: V8
  • Displacement: 6.37L/388 cu. in.
  • Horsepower: 1,021hp at 6,800 rpm
  • Torque: 471 lb/ft. at 6,800 rpm
  • Max RPM: 7,500 rpm
  • Transmission: Viper six-speed manual

Currently the Mule can be seen on display at the Audrain Automobile Museum in Newport, Road Island

About the author

Nicole Ellan James

As an automotive journalist and avid car enthusiast, Nicole Ellan James has a passion for automotive that is reflected in every aspect of her lifestyle. Follow Nicole on Instagram and Facebook - @nicoleeellan
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