Justin’s RX-7: Domestic Dalliance

After league night at the local indoor karting track started to feel a little repetitive, Justin Merritt began considering his options. He’d always wanted to jump into track driving, and with the foundation laid by lots of wheel-to-wheel kart battles, he felt ready to step into full-sized sports cars. With his Scion FR-S, he moved rapidly out of autocross and into HPDE at Sonoma and Thunderhill, the two closest tracks to his home in Reno.

After making the usual list of track mods, he felt he started to see the short-term potential of the car. Truth be told, he’d gotten tired of his friends in fast Mustangs 5.0s leaving him on any straighter sections of the track, and so decided to make a shift into a sportier platform.

Weighing only 2,750 pounds wet, this V8-powered RX-7’s acceleration put him ahead of his Foxbody-driving friends.

The car had to be sensible, though. Justin hadn’t splurged for a truck and trailer yet and so he wanted to be able to make the trek over the Sierras in some comfort – at least the comfort of knowing his car wouldn’t likely leave him stranded. He’d had a thing for old RX-7s. The FC, in particular, and its doorstop shape left him feeling a little smitten.

Though he was in no position to start and finish a complete V8-swap, the thought of that had stimulated his imagination. Unfortunately, most of the typical examples of V8-swapped FCs have lived hard, unloved lives, and he knew better than to get involved with a thirty-five-year old Mazda with cut corners.

He had the good fortune of finding a half-completed ’89 that had an LS1 conversion underway. Along with the 5.7-liter in place, the previous owner had fitted a Tremec T56, a few cooling modifications, and a questionable exhaust setup.

The car’s wiring needed work, though. Whatever – the cost and the promise of a lightweight, rear-drive sports car with a fairly modern Chevrolet LS motor was worth sorting out a rat’s nest.

JTR headers, the custom y-pipe and 3” exit, a Summit CAI, and a tune from Gabe at Real Performance in Reno, Nevada, net 320 whp and 330 lb-ft of torque.

The ECM received no signals regarding coolant temperature or oil pressure, and the connector to a coil harness, well, one of its pins had backed out and caused a misfire. All fairly simple fixes. The ECM, as he found out, wasn’t even bolted down.

Once the electrical gremlins were sorted, Justin had to address some of the shoddy exhaust work. Some tubes were round, some were square, and they leaked everywhere. He left these to his fabricator friend, who added a set of JTR longtube headers, a custom y-pipe, and an HKS 3” single exit.

When all those issues were resolved, Justin had the confidence to start using it as an occasional daily. However, it was on stock suspension, so it nearly wheelied every time he stood on it.

When the time was right, he threw a set of BC DS coilovers (8k/6k) as well as the entire Parts Shop Max catalog at it. The adjustable rear toe links, adjustable toe and camber rods, new wheel bearings, a set of special bushings to do away with Mazda’s active toe, trailing arm bushings, and the typical swaybar bushings and front control arm bushings made a night and day difference.

To cap the first round of modifications off, he opted to install the larger four-piston Turbo II brakes along with Hawk HP+ pads and Stoptech rotors. The item tying these simple but effective braking mods together was the Chase Bays booster delete kit, which improved feel as well as offered the ability to change the brake balance with its proportioning valve.

“I didn’t know why there was a rattling noise coming from the passenger’s footwell until I noticed the new carpet and decided to look underneath it. There it was: the ECM, unbolted and bouncing around like a soda can.”

That helped set the nose, as did a reasonably wide track up front 255-section Kumho V730s at the end of the front axle, and 265-sections Falken RT660s at the rear.

The aluminum V8 isn’t the heaviest motor around, and though somewhat longer than the rotary it replaces, it doesn’t seriously disrupt the RX-7s famous balance and responsive front end.

That footprint proved more than adequate on the autocross, where he found he didn’t have much difficulty putting that power down. Not too shabby considering the car still runs an open differential.

Where it struggled slightly was in cooling. “I thought the big Spal fans and Griffin radiator would be fine on their own, but it overheated on hot days. I looked a little closer and saw that the radiator needed some ducting.”

With a little homebrewed ductwork and a few blockoff plates, he could redirect the air into the cooler and keep the LS happy in any temperatures. During his first outing at Thunderhill West, he was able string enough laps together to get a sense of the line, and went quickly enough to lap the clockwise configuration in 1:32.

It’s been an exciting eighteen months with the car, but it’s now looking for a new home. The reason? Justin’s looking for a new home of his own. A down payment must take precedence over a track toy, so anyone in the market for a nicely sorted, lightweight, visceral track RX-7 with the perfect amount of power ought to take a look at its listing.