Image Credit: Mecum.By 1973, America's muscle-car horsepower war was rapidly cooling down. Chevrolet's hottest factory Camaro that year was the Z28, and its 350-cubic-inch V8 was rated at 245 net horsepower.Motion Performance laughed at that pitiful number. The legendary New York speed shop was still willing to build the kind of Camaro that looked increasingly out of place in an era of tightening emissions regulations and declining factory performance.The result was the Motion Phase III, and the Medium Orange example pictured here packs a 454-cubic-inch LS6 V8 rated at 513 horsepower. Its odometer currently shows just 5,361 miles, although the car underwent a restoration during the 1990s.Now this rare piece of modified muscle-car history is looking for another owner. Mecum will offer it as part of the Dan McMichael Baldwin-Motion Collection at its Kissimmee 2027 auction, where it's scheduled to cross the block on January 15.513 HP In 1973 Was Serious BusinessImage Credit: Mecum.The Camaro's LS6 is equipped with an Edelbrock C427X intake manifold and Holley 850-CFM four-barrel carburetor. Inside are TRW pistons providing an 11:1 compression ratio, while a Mallory dual-point ignition handles the spark.The 1 3/4-inch Super Comp headers feed a side-exit exhaust system. Power reaches the rear wheels through a heavy-duty Turbo 400 automatic with a manual valve body, high-stall converter, and external cooler.A 12-bolt rear axle with 4.10 Positraction completes a drivetrain clearly designed with acceleration in mind. Power steering and power front disc brakes provide at least a little civility.The visual treatment is equally difficult to miss. There's an enormous high-rise fiberglass hood, side exhausts, and 15x8-inch Cragar SS wheels, while the cabin gets a wood-rimmed steering wheel, Hurst T-handle shifter, and Sun tachometer.It Cost More Than Twice The Original CamaroImage Credit: Mecum.Transforming an ordinary Camaro into a Phase III wasn't cheap. Mecum's documentation shows the car originally carried an MSRP of $3,841 before Motion Performance went to work.Once the modifications and sales tax were included, the total bill reached $9,073.33. That's $5,232.33 beyond the Camaro's original sticker price and illustrates just how serious its first owner was about performance.Its history is unusually well documented today. The sale includes copies of the original shop orders, a Motion Performance Letter of Authenticity, and a copy of the original purchase order from Park Chevrolet in Asbury Park, New Jersey.Restored With Help From Mr. MotionImage Credit: Mecum.This isn't an untouched 5,361-mile survivor. Mecum says the Camaro was restored during the 1990s under the supervision of Motion Performance founder Joel "Mr. Motion" Rosen, whose signature now appears on the roof above the driver's door.The car subsequently appeared in the Winter 2002 issue of Camaro Performers and was displayed at the 2012 Ault Park Concours d'Elegance. It was also invited to the 2017 Amelia Island Concours d'Elegance and appeared at the 2025 Muscle Car and Corvette Nationals.Mecum hasn't published a presale estimate, so it's anyone's guess what someone will pay for it. Between its documented Motion provenance, period-correct excess, and 513-hp LS6, however, this isn't exactly your average 1973 Camaro. At a time when factory muscle was being toned down, Motion Performance clearly didn't get the memo.If you want more stories like this, follow Guessing Headlights on Yahoo so you don't miss what's coming next.
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