LS1 Powered Mazda RX-7

Bastard. The strict definition simply means a child born out of wedlock. In modern slang, however, it has come to mean a downright despicable person. You know, a bastard, like the guy who decided to put a Camaro on the cover of this magazine. But bastard can mean "not genuine, fake," or "resembling a known kind of species but not truly such." So when we call this LS1-powered Mazda RX-7 a bastard, we are right on so many levels, even though we mean it in the nicest sort of way.

Does such blasphemy actually happen? Believe it. RX-7 tuners are doing the unthinkable: switching out the beloved, cult classic 13B rotary engine for the knuckle-dragging, pushrod-pumping LS1 V-8. Of course we had to investigate-and compare one such bastard with a real rotary. Though the swap is becoming increasingly common with both second- and third-generation RX-7s, we chose a pushrod-powered FD3S, because these chassis are highly regarded by enthusiasts and, well, dead gorgeous.

The RX-7 we have deemed Bastard is gold in color and owned by Duy Le, marketing manager at Injen, the aftermarket intake manufacturer. It is fairly heavily tuned by street-car standards, with a rollcage, stripped interior, and some minor bolt-ons. Up against the Bastard is the prodigal son, a highly tuned rotary RX-7 that served as the primary drift/track car for Falken-sponsored Formula D driver Calvin Wan. For a look at the other side of the bastard's family tree, we also brought along an '01 Chevy Camaro SS.

How is an aberration such as Le's Bastard created? It starts with a used RX-7. It's common knowledge that RX-7s aren't the most reliable cars around. Blown apex seals and overheating are frequent problems, but more often it is poorly executed tuning or over boosting that turns the 13B into an IED. With FD chassis sans blown engines going for little more than a few thousand dollars, swap-happy enthusiasts have been snapping them up and creating a cottage industry for LS1 recyclers.

Le didn't go the blown-rotary route, opting instead to switch out his fully functioning 13B because he was bored and a little frustrated with it. He first heard about the performance advantages of the LS1 swap from an RX-7 online forum. "It was funny, everyone was attacking this guy on this [LS1-swap] thread," says Le, "but he defended his thoughts pretty well and introduced one of the first guys to put it all together, Brian Hinson, and the whole theory appealed to me." Le continues, "When you lay everything out on paper, it just makes sense. The advantages are mainly the low- to midrange power gains and the fact that the weight distribution remains almost the same."

Once committed, Le found a clean LS1 from an '01 Corvette, although he says a Camaro SS LS1 makes for an easier swap, since the SS throttle body and oil pan are needed to clear the hood and subframe. Le installed the engine into his RX-7 with a conversion kit from Hinson Supercars, which contained a modified subframe, a transmission brace, and bumpsteer correction. They also sell the necessary cooling system upgrades and the radiator. Le threw some Injen intake and exhaust parts on the car and mated a SPEC clutch and flywheel to the six-speed T56 transmission. After gutting the interior and adding a rollcage, the Bastard only weighs 77 pounds more than Wan's drift car, which is even more stripped down.

In comparison, Wan's car was transformed from a parts car into a full track/drift racer by Motorsport Dynamics. The motor, drivetrain, and suspension came off of Wan's previous red D1 drift-spec FD3S. Power comes from a 13B-REW modified with an A'PEXi AX75F82 turbo and a Rotary Extreme intercooler.

The Camaro belongs to B&M design engineer George Lara. Since this is his daily driver, it's only lightly modified with an intake, headers, and exhaust. And, gasp, it's got an automatic transmission. So it doesn't really compare to the other two cars, but you probably didn't care about it anyway.

As you'd expect, we did a thorough evaluation, starting with dyno tests. Then we brought in pro driver Andy Hope for performance tests at California Speedway and hot laps around the Streets at Willow racetrack.

The Bastard takes the overall win in the dyno tests, cranking out 347hp and 346 lb-ft of torque at the rear wheels with plenty more room in the rev range. The rotary RX-7 has more horsepower, at 351, but only puts out 299 lb-ft of torque. The big surprise was the Camaro SS, which makes 332hp and 340 lb-ft at the rear wheels, a testament to the power of the GM small-block. Or maybe the surprise is that the Bastard's numbers seem a little low; a stock '01 Covette makes 350 bhp and 375 lb-ft at the crank and given the modifications to the Bastard's powerplant we expected a little more. Then again, there's more to it than numbers. The Bastard has a broad, flat torque curve that starts at 300 lb-ft at 2,000 rpm. In contrast, the rotary's torque curve looks like Britney Spears' career: a steep ramp up with a short peak followed by a fast decline. But unlike Mrs. Federline, the RX-7 is still as skinny as it was the day we first fell in love with it.

The LS1 is a more tractable engine, period. And the first place this shows up is on the dragstrip, where the Bastard made easy, consistent launches. The rotary's peaky nature made it tough to get the turbo spooled without lighting up the tires, and our failed attempts were "decent to embarrassing." Still, the best rotary run was dead even with the Bastard. How can this be? One reason could be the tires; the rotary FD was running on ultra-high performance Falken Azenis RT-615 rubber, which is designed for exactly the dry track conditions we experienced, while the LS1 FD was shod with far-less-grippy BF Goodrich KDWs, a wet/dry high-performance tire. Throw in the fact that the Bastard is much more able to spin tires with its newfound torque, and we may have the answer. Though shod on Dayton Daytonas, the Camaro SS was easy to launch, but the tires, slushbox and extra 800 pounds meant an extra 0.9 seconds to travel all 1,320 feet.