Michael Johnson
Associate Editor, 5.0 Mustangs & Super Fords
June 18, 2012
Photos By: Henry DeKuyper

We have a soft spot for Roush Performance's '10 540RH, affectionately known as the Hammer. We covered our extended Hammer road test in the July '10 issue ("Sleeping Giant," p. 120), and came away dazzled by the car's road manners mixed with brute horsepower. With a TVS-supercharged Three-Valve built to withstand boost, the Hammer is a fun car to drive even in stock form.

We had more fun than should be legal, and I know several laws were bent under our right feet. Out of the box, we were able to extract 11.70s at over 120 mph out of the car. What's more, when we had it dyno'd for the article it was clear there was more power available with tuning.

All we wanted to do was tell Roush Performance we needed the car as a long-term tester. That way, we could dig into the car even deeper, and add pulleys, a tune, some sticky tires, and really get after it. However, we're sure Roush would have frowned on our request.

Since we were unable to explore the Hammer's untapped potential, we're glad Shawn Assavedo took it upon himself to wring out every last ounce of performance from his car. He has definitely shown us the way.

Shawn owns an oyster-distribution company in Saint Bernard, Louisiana, so he stays busy. Not too busy to keep him from owning his fair share of Mustangs, though. He had never owned a Roush Mustang, so he set his sights on owning one of Jack Roush's best. He chose the 540RH for a variety of reasons. First off, he knew it would be a one-year only offering being a 2010 model, and that exclusivity intrigued him. Second, he knew Roush fortified the engine's bottom end with beefier components, so building an engine wouldn't have to be in the future plans. Shawn knew he was only a few performance enhancements away from a really fast Mustang.

Who would help him reach his goals? He wouldn't have to look far. Asking around, and even talking to Roush Performance, he was pointed in the direction of Stang-Hi Performance in Baton Rouge, Louisiana. Stang-Hi is known in that area for its prowess with Roush cars, and Mustangs in general. Cody Cutforth and the Stang-Hi gang took in Shawn's 540RH, naming it Project Hammer.

All the aspects we wanted to improve on our loner Hammer Stang-Hi did to Shawn's 540RH. First thing Stang-Hi did was a pulley and custom tune upgrade. When we dyno'd our loaner 540RH we could tell there was room for more power right off the bat. Undoubtedly, Cody was able to make a substantial gain just from a pulley and tune. Then came a Stang-Hi Performance cold air intake, and American Racing Headers 1-3/4-inch long-tube headers with a matching 3-inch X-shape crossover pipe.

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Each progression was made in the name of improved performance without giving up daily enjoyment. With the power Stang-Hi was able to get out of the car, the stock Cooper rubber didn't really stand a chance, so stickier rubber got the nod for street and track. Under Stang-Hi's tutelage, the Hammer went from mid-12s to mid-10s. With just the performance additions, the car ran in the 10.90s, but once the car received BMR Suspension's Xtreme antiroll bar and lower-control-arm relocation kit, along with Strange Engineering shocks out back, a return strip trip resulted in 10.50s at 135 mph with a 1.58 short time.

"The car is ridiculous," Cody says. "We basically took a stock Roush Hammer and massaged it," he adds. That's the great thing about a car like the 540RH Hammer--it was built to take more power than it came with, and it wouldn't take much to make big power. What Stang-Hi did to the car took it from a fun car to an animal on the street.

Unfortunately, because of his busy oyster business, Shawn doesn't really have a lot of time to drive the car. He says it probably doesn't even have 2,500 miles on it. I had to have him repeat that number when talking to him about his car for this feature, but it's true, he doesn't get to exercise it often. That doesn't mean he's done with it, though. Shawn says the plan for the car is to run 9.99. After that, Shawn's sending us the car so we can give it the business. Hey, we can dream.

Horse Sense: Stang-Hi Performance's Cody Cutforth helped out yours truly when a friend of the magazine needed a car checked out. Cody went over the car, which was a '96 Mystic Cobra, and gave it his seal of approval. That same car just might become the subject of an engine build-up by the time you read this.

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5.0 Tech Specs

'10 540RH

Engine and Drivetrain
Block Iron
Crankshaft Roush Performance forged
Rods Forged H-beam
Pistons Forged aluminum
Camshafts Roush Performance
Cylinder Heads Roush Performance Three-Valve
Intake Manifold Roush Performance
Power Adder Roush Performance R2300 RouschCharger (featuring TVS technology) w/ 4-pound lower pulley and Roush intercooler
Fuel System Roush Performance twin GT500 fuel pumps, Roush injectors
Exhaust American Racing Headers 1 3/4-in long-tube headers w/ 3-in X-shape crossover pipe, and Roush Performance axle-back
Transmission Stock w/ SPEC Stage 3+ clutch, aluminum flywheel, Roush Performance shifter, and Dynotech aluminum driveshaft
Rearend Stock 8.8 w/ 3.73 gears

Electronics
Engine management Stock PCM w/ SCT X3 Flash Tuner and Stang-Hi Performance custom calibration
Ignition Stock w/ FRPP spark plugs
Gauges Roush Performance boost gauge in vent pod

Suspension and Chassis
Front suspension
K-member Stock
A-arms Stock
Struts Roush Performance
Springs Roush Performance
Brakes Roush Performance
Wheels CCW Drag Pack
Tires Mickey Thompson
Rear Suspension
Shocks Strange Engineering
Springs Roush Performance
Control Arms Roush Performance w/ BMR Suspension control-arm relocation kit and Xtreme antiroll bar
Brakes Roush Performance
Wheels CCW Drag Pack
Tires Mickey Thompson