1994 Mazda RX7 (FD3S) R2
with 2001 LS1/T56 and Cobra IRS
421 RWHP / 408 RWTQ @ 2850 lbs with M2 Roll Bar
At 5.6 lbs/crank hp, a better power-to-weight ratio than a 7L Z06, Viper, or 911 turbo
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This is one of the cleanest and most methodical builds of an LS1RX7 you will find. It is a Hinson-based LS1/T56 conversion with a modified motor that puts down a peak of 430 rear-wheel horsepower at 6100 RPM and a very flat torque curve that tops out at 410 ft-lbs based on a conservative tune. This equates roughly to 500 HP and 480 ft-lbs at the crank. This car features one of only a very few working Jim LaBreck Cobra IRS conversions—and it has been specially modified for increased strength and streetability. The body is in near-perfect condition and retains the factory paint. The exterior is unmodified. The frame is straight and the car has never been in an accident. The conversion began with a completely bone-stock car with 96,000 miles. The car now has just under 101,000 on the odometer.
The GM driveline came from a 2001 Firebird WS6 with 21,000 original miles. The engine was partially disassembled while upgrading to new heads, cam, pushrods, conrod bolts, timing chain, and other extras. Visual inspection of the motor during disassembly showed no appreciable wear, debris, or damage. The engine was reassembled, torqued, and fired right up when installed.
Only the best components were used in the build. AFR 205cc heads, an F13 Futral cam, ARP studs and bolts, and Sanderson 1 7/8 ” long-tube headers were used. A stainless Racing Beat exhaust with a custom resonated mid pipe keeps a stock appearance and mellow tone under cruising. The Cobra IRS has been built with a Torsen T-2R differential, a Ford Motorsport 3.73 ring gear, and a Mark Williams 1350 billet yoke. The driveshaft is a Denny’s 3.5” HD racing model, and the axles are 300M hybrids. The driveline is good for well over 600 ft-lbs of torque.
The suspension is a custom-valved Function X package from Endless/ZEAL coil-over package that features 30-way adjustment of bump and rebound damping. Tri-point, Racing Beat, and Widefoot sway bar components are used. M2 trailing and toe links are installed in the rear. The notorious rear pillow ball bearings have been completely replaced to eliminate any suspension noise. A custom-built power steering pump is used in conjunction with the factory steering rack. Two sets of 18-inch wheels—SSR GT7’s and CCW Classics’s—offer an easy switch between street and track driving, both with the best Michelin tyres available. (The OEM wheels are also included.)
A matched set of Bosch 42-lb injectors ensure proper fueling with room to grow for future upgrades. The injectors are fed by an in-tank Nippodenso fuel pump with a new relay system. An Aeromotive regulator keeps the pressure solid at 58psi. Earls fittings and lines are used on the tank and in the engine bay.
The extremely clean interior features R2 seats, A full M2 4-point roll bar, SPA dual digital gauges in a custom center pod, and a Clarion 7” flip-screen with iPod integration in the glove box. The Odyssey dry-cell battery has been relocated to the driver-side rear bin with a one-of-a-kind CNC battery tray—and is a full-size battery for reliable starts. Full 1/0 gauge wiring is used to the engine bay, and a battery kill switch is also employed for safety and security.
The car has been tuned by a local LS1 specialist and comes complete with the latest MVPI-enabled HP Tuners VCM suite which includes hardware, software, and interfaces to allow compete tuning of your car—even in real-time.
The factory pop-up lights are retained, but a custom-designed dual Hella 90mm system with HID low beams that provide a dramatic improvement over the stock lighting.
This car has over $50,000 invested over two years of the build—and hundreds of hours of my own time in design, installation, wiring, and tuning. This is an extremely clean and unique LS1 conversion.
