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Tech Review—Coan Billet Aluminum Powerglide Valvebody

Coan Engineering’s Powerglide billet valvebody is designed as a lightweight, quick-reacting, and top-performing unit for the market. It is built for anyone running a GM Powerglide —as many in NMRA or NMCA competition do — with the objective of quicker elapsed times.
By Miles CookPhotos

Courtesy of Coan Engineering

Founded in 1976, Coan Engineering is a well-known presence in drag-racing circles. The company has long focused on transmission performance, reliability, and commitment to its customers, who range from street-car enthusiasts to those racing in the NMCA and NMRA series.

Coan played a major role in introducing the first transbrakes for the GM Powerglide, TH400 and TH350 transmissions, which are now a standard in the industry. The company also pioneered the use of steel stators in its high-performance torque converters to withstand the rigors of the high-horsepower levels in today’s performance machines. Coan is also one of the few companies to offer the precise design of steel stators necessary for a 7-inch torque converter used by many of today’s class racers.

Among GM transmissions used for racing, the two-speed Powerglide has been a workhorse in the drag racing community soon after it was introduced in the early 1950s. You can get just about any part you want for a Powerglide from the aftermarket, and Coan offers a valvebody for this transmission in billet form with many updates for better performance.

All circuits in the valvebody have been exactly sized to ensure fast transbrake setup, quick shifts and quick transbrake release. An integrated adjustable pressure regulator also allows the valvebody to be tuned to its application. To help facilitate this, Coan also has a car spec form on its website.

Coan is known for creating high-quality aftermarket parts for transmissions, so it’s no surprise the company brought forth this billet valvebody for the Powerglide. With OEM castings getting harder to come by, Coan took 40 years of modification knowledge and make a better valvebody for the Powerglide. This new unit offers an improved reaction time to pressure changes, a better transbrake setup time, and an updated pressure regulator, which makes this new billet valvebody a significant upgrade for the Powerglide.

“This valvebody offers a notable seven pounds of weight savings over a cast unit. It has a better filter design where it’s toward the back of the fluid pan to prevent fluid cavitation during acceleration,” Jason Coan, of Coan Engineering, said. “By going to a billet unit, we’re able to enhance the fluid circuitry of the valvebody and the timings are all enhanced that come with that. We also kept the charge circuit similar to the cast iron valvebody so if a racer is switching from a cast-iron unit to our billet version, the converter won’t act differently.”

Clearly Coan is committed to offering top performing and reliable automatic transmissions, torque converters, and components and these billet Powerglide valvebodies are no exception.

Unlike some aluminum valvebodies, the Coan unit supplies regulated converter charge oil to ensure torque-converter behavior and operation is unaffected.

Coan Engineering

Mike Galimi
Mike Galimi
Mike Galimi is the Director of Content & Marketing at ProMedia Publishing and Events with nearly 20 years of experience in motorsport writing and photography.