While Ford was busy working on its extensive redesign of the Mustang for 2010, there was a large fly on the wall of the engineering center. His name was Jack Roush.

Thanks to the bagfulls of trophies Roush's racing programs have delivered to Dearborn over the years, the tuning division of his automotive empire, Roush Performance, was given the kind of insider access to development of the new 'Stang that other aftermarket companies would trade their entire supply of torque wrenches for.

Click here for an interview with Jack Roush

The first product of this cooperative is the 427R, a heavily reworked version of the Mustang GT aimed at drivers looking for a little more from their pony car experience than the factory ride provides. It's a $14,156 package that turns Not-So-Old Paint into a Kentucky Derby contender.

Click here for VIDEO of the 427R at Pocono Raceway

The biggest changes take place underhood, where Roush adds a custom intake manifold, cold air induction system, and an intercooled Roots-type supercharger running at 5 psi pressure that increases the number of horses on tap from 315 hp to 435 hp, with an accompanying bump in torque from 325 lb-ft to 400 lb-ft. Since the 4.6 liter engine is basically a carryover from 2009, the modifications are similar to the ones found on last year's 427R, but integrated more neatly than in the previous edition.

The 427R gets a full rework of the suspension with new struts, shocks, springs, sway bars and an anti-hop kit all tuned for better handling in the twisties, while a functional front splitter and decklid spoiler give them more downforce to work with. A new fascia, side skirts and rear valance panel are for appearance only, and do a good job at that.

Standard interior changes are limited to custom floor mats and billet aluminum on the pedals and shifter handle, but the example I spent the day with at Pocono Raceway was fitted with an optional short-throw shifter topped by a billiard-ball knob, white guage faces - including the one on the boost gauge integrated into the far left vent pod - and Alcantara over leather seats that are stuffed with firmer foam than stock to help keep you in the saddle.

Click here for PHOTOS of the 427R

The test car also had an optional exhaust system that may be the best use of $710 this side of a Marshall amplifier. Light up the V8, blip the throttle, and revel in the scene as startled onlookers scatter from the roar, then converge on the car to bathe themselves in the deep burble provided by the twin pipes. It’s a sound usually reserved for pit lane and, since that's where we were, it fit right in.

Drop the light clutch, lay some rubber, and the power upgrades immediately become apparent. The engine pulls strongly from idle and keeps going all the way to its 6,500 rpm redline. I hit the rev limiter an embarrassing number of times throughout the day, partially because the motor didn't feel like it was ready to give up, but also due to how quiet it is from inside the cabin, even at the top end.

The absence of supercharger whine is almost a disappointment, but a testament to the levels of refinement in the new Mustang, and Roush’s engineering prowess. That said, anytime I got near the retaining wall with the windows down and the pedal to the floor, the thunder from the exhaust was so resounding that I started to worry about the weather.

Through the first right hander that leads into the infield section of the road course, and the ones that followed, the 427R rolled a couple of degrees more than you might expect from a car with a pedigree like this one has, but not much, and it always settled into a neutral stance. Understeer is very controllable, and good luck finding a car with this much power being fed through a live rear axle that is less tail-happy. The setup is a fair bit firmer than stock, but remains more street than track. This was as welcome on the lumpy, patched, mixed media surface of Pocono as it would be on the winter-beaten Michigan roads surrounding the Roush factory in Livonia.

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Nevertheless, I had no problem keeping pace with the bevy of Corvettes on hand at the track day event I took part in, not to mention a couple of older Roush Mustangs, and I'm no Carl Edwards behind the wheel. The 427R is a pleasure to drive quickly, and while it might not be primed for fastest laps, powering it through increasing radius curves is ear-to-ear grin-inducing.

Even with the $2,877 "Big Brake Upgrade", though, the 427R feels like it can stand an extra dose of stopping power. That is if you plan to present it with situations where it needs to slow from 135 mph to 35 mph on a regular basis. The 14-inch front rotors with 4-piston calipers do a noble job, but never go above and beyond. The same can't be said about the traction control system.

The 427R retains Ford's AdvanceTrac which can be shut off completely, but since the track was a little wet, and this was the only 427R in the Northeast, I decided to ignore that option. There are two levels of stability control available, the more lenient of which allows for a fair amount of slip from the rear end before chiming in. Unfortunately, coming out of the 100 degree+ corners that lead onto Pocono's straights, it bogged down the potent engine just as I was about to rocket away, leaving my dreams of hitting the car's 143 mph top speed limiter for another day.

That last figure may sound a little low, but with it Roush is able to retain Ford's 3 year/36,000 mile warranty and extend it to all of the modified parts, a major advantage in the aftermarket scene.

Click here for a full review of the 2010 Mustang GT

All told, the loaded 427R I drove was priced roughly $22,000 over the base Mustang GT, putting it near the 50 grand mark. That kind of coin can get you into a Shelby GT500 which has 540 hp, but also weighs nearly that many more pounds than the Roush. So, if the comparison isn't exactly apples and oranges, let's call it tangerines and oranges and thank goodness we still have the choice as we near the end of fossil fueled days.

In any case, if you want to cruise to the track now and then, the 427R is an immensely satisfying ride and a definite step up from the GT. If the open road is more of your thing, you might want to skip the big brakes and order the $2,200 radar/laser defense system, complete with a laser jammer. You never know when someone is looking over your shoulder.

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2010 Roush 427R Mustang

Base Price (approx): $42,000

Type: Front-engine, rear-drive, 4-passenger, 2-door coupe

Engine: Supercharged 4.6L V8

Power: 425 hp, 400 lb-ft torque

Transmission: 5-speed manual

What do you think of the 427R?

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