Owner:

Mark Burt

Year:

1988

Make:

Mazda

Model:

RX-7

Weight:

2,850 with driver

Engine:

GM L33 from 2005 Silverado 83,000 miles, 300 whp

Suspension:

Front: Coilovers with Hypercoil springs

Rear: Coilovers with Hypercoil springs

Tires:

245/40-17 on Mustang GT 96-04 wheels

Brakes:       

Front: Custom Wilwood 13″ x 1.25″ for time of photo, 14″ x 1.25″ current upgrade being tested

Rear: Custom Wilwood 12.88″ x 1.25″

Data system:

Sits in the driver seat

Sponsors:

Visa and Mastercard

Walking past Mark Burt’s 1988 RX-7, you might not look twice, but if you do, you find that he replaced the rotary engine with a L33 LS engine from a 2005 Silverado Z71 pickup. Look closely under the hood and you’ll see that the installation is so neat, so fastidious, the V8 engine almost looks like original equipment.

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The cool part is that Burt made most of the parts himself, sourced parts from various places and sorted out all of the modifications to make the whole package work as a racecar should. He bought the car in Tampa, Fla., for $300, with no engine or transmission. He knew exactly what he wanted to do with it even before he bought it.

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“That was already in my mind,” Burt said. “A few friends and I were going to do the same thing. We were going to build three matching cars, but of course that didn’t work out. Mine’s the only car finished.”

The car is a mechanical Frankenstein, but everything is put together so well you’d never know it to look at it. On the outside and inside, the car has the proper patina of a racer. Mechanically, however, it’s buttoned up and bulletproof, despite the diaspora of parts that went into the build.

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For starters, it has a truck engine with an F body oil pan, an LS6 intake manifold, a Quick Time bellhousing that adapts the Borg Warner T-5 transmission from a Mustang. One part that makes the installation look so professional is also one of the cheapest. The plastic intake at the front came off a mid-1980s Camaro Z28. He paid $12 for it. He also got a radiator fan from a 1985 Fiero, which is operated through the ECM, as is the fuel pump. The powertrain is good for 300 horsepower at the wheels, which is ample power for a 2,850-pound car.

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“It’s a little heavy,” Burt said. “It’s still a street legal car, with full glass, pop-up headlights and turn signals and all that fancy stuff.”

It uses a Wilwood clutch and brake pedal set that operates a hydraulic cylinder that pushes on a throwout fork from an SN95 Mustang. The flywheel and pressure plate come from an LS1, and the disc was originally found in a 1988 Ford Bronco, which Burt bought for $22 at Rock Auto. He went with Wilwood pedals because he knew he’d need more stopping power.

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“I wanted dual masters for the brakes, so I could play with bias a lot easier,” Burt said. “I knew the stock brakes, which were 10.75 inches in diameter, weren’t going to hold up over time, so I knew big brakes were in my future. So when I built the car, it just made more sense to upgrade the pedal assemblies. That way I can make it work in the future for whatever I change, without much hassle.”

He made the brackets to adapt the Wilwood calipers to the factory knuckles up front and the uprights in the rear. Getting big brakes on the car was a challenge because of the size limitations of the wheels, which are originally from an SN95 Mustang.

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For downforce, Burt added a rear Kognition wing. He made the uprights that hold the wing in place on a friend’s CNC machine. He was able to do that because he got the CAD drawings from Kognition, then custom made the uprights. He then welded the uprights to custom-made brackets that fasten it to the car.

“It does work well. It actually is noticeable,” he said. “The car went from high speed loose, like in Turn 1 at Sebring, to high-speed push, so it required me to build a splitter for the front.”

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So he made a splitter for it out of 1-inch by 1-inch square aluminum frame sheeted with 1/32 inch aluminum. The whole assembly is removable with six bolts so he can load it on the trailer. He also made the struts that hold the splitter in place. He machined solid aluminum rods, drilled and tapped them and screwed in quarter-20 rod ends. Craftsmanship is evident everywhere you look.

Even inside. He made the dashboard from sheet aluminum, adapted the stock steering column and cut and bent all the tubing for the cage. His father welded it for him. Burt made front and rear wiring harnesses and relocated the ECM and fuse panel. He also made the fire bottle mounting brackets, the battery box lid and the rear strut tower brace.

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The car works well as is, but as you might imagine, he’s considering more upgrades, sourced from salvage yards or handmade, of course. He’s going to be adding a differential from a Ford Explorer, which has an 8.8-inch ring gear, and he plans to lighten up the clutch assembly as soon as he figures out where to source the parts.

“I still need more downforce, too,” Burt said. “I’m currently trying to develop canards for the front of the car to see what I can do to get a little bit more front downforce. I’m probably going to end up making three or four different ones.”

Of course he is.

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Image courtesy of Brett Becker