Video: This IRS-Equipped Foxbody Autocrosses With The Best Of Them

When you raced motocross throughout your teens, twenties, and thirties, you don’t just slide into a middle age full of afternoons playing bridge. Mike Trenkle’s aches and pains were just a minor setback in his eyes. True, he had to quite the two-wheeled abuse, but he kept the adrenaline drip going through a Foxbody. With no expense spared, Trenkle improved the suspension, widened the footprint to the point of absurdity, and fitted a great motor that responds like a racing engine should.

A custom widebody kit brings the weight down to a respectable 3,200 pounds.

The engine isn’t wild by modern standards, but there’s only so much grunt that can be used on a cone-lined course. Trenkle stuffed a Ford Performance Boss block with lightweight SCAT H-beam rods, a custom cam, and Probe pistons. The engine was topped off with Ford Z heads and tidied it all up with ARP hardware. The FAST fuel injection helps the 363 Windsor make 550 horsepower and 480 lb-ft of torque. That shove is then sent through a Centerforce DYAD clutch, a revised TKO 600 transmission, and a Ford 8.8-inch rear with a Wavetrac differential. Best of all, it spins to 7,000 revs.

Fancy Footwork

The motor is fine and dandy, but the real draw with this machine is the suspension, wheels, and tires. The filled fenders and broad footprint are a giveaway that this is a developed cornering machine, but closer inspection reveals how it differs from every track-oriented Foxbody out there. Underneath that boldly liveried skin is a combination of a Cobra independent rear suspension and a cantilever configuration rear end. This allows him to stuff 335-section tires under those widened haunches.

Trenkle runs the same width tires in front, which help with its extremely crisp turn-in. The SLA suspension up front is an aid there, too. Of course, so much of this comes down to some top-shelf Penske shocks, which reportedly transformed the car. “Honestly, it rides just as well as my 2017 Mustang Performance Pack. It’s a testament to the quality of those incredible Penskes,” said Trenkle.

Minimal understeer and lift-off oversteer help this broad Foxbody point around a cramped cone course.

Still Comfy

A Mustang built to this level may not qualify as a street car in all eyes, but Trenkle went to some lengths to keep it somewhat civil. The four-point cage isn’t too obtrusive, and the Sparco fixed carbon seats aren’t iron maidens. A thick layer of Dynapad sound insulation mitigates the mild exhaust drone. Full carpet, a nine-speaker sound system, RestoMod Air Conditioning, Dakota Digital gauges, and a Retro Sound two-post deck make cruising a treat, not a chore.

After seven years of development and countless afternoons spent carving cones, this Foxbody is now a front-running SCCA autocrosser and major contender in the Optima Ultimate Street Car Challenge. In fact, it’s racked up quite a resume in a short span. Multiple SCCA national tour wins, two SCCA SOLO national podiums, several regional autocross championships, and even a few SEMA appearances are just some of the accolades Trenkle can be proud of.

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About the author

Tommy Parry

Tommy Parry has been racing and writing about racing cars for the past seven years. As an automotive enthusiast from a young age, he worked jobs revolving around cars throughout high school, and tried his hand on the race track on his 20th birthday. After winning his first outdoor kart race, Tommy began working as an apprentice mechanic to amateur racers in the Bay Area to sharpen his mechanical understanding. He has worked as a track day instructor and automotive writer since 2012, and continues to race karts, formula cars, sedans, and rally cars in the San Francisco region.
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