JAMMING big-cube V8s into nimble, sweet-handling little cars has been a recipe for success for decades now, but particularly so with the LS V8, with its small, light format, cheap purchase price and aftermarket support. Kevin Jensen knew all of that when he threw out this Mazda RX-8’s stock asthmatic rotary and replaced it with a six-litre Gen IV V8.
This article was originally published in Street Machine LSX Tuner #5
“I bought the car after returning from living in Denmark for two years,” explains Kev, a qualified mechanic. “I had been off the tools for a while and was keen on getting into a conversion when I returned. I had my heart set on an LS swap, because after always playing with Japanese engines I wanted to try something new.”
Of the many mid-size Japanese and European sports cars, the fad for LS-swapped Mazda RX-8s has really taken off of late. With a four-door format and crisp-handling chassis, the late-model rotary sportster is a second-hand bargain, as JDM fans still prefer the older two-seat RX-7. But Kevin admits he wasn’t dedicated to the Mazda platform when picking a car to build.
“While I was set on the engine, I had to find a car to suit,” he says. “I wanted something modern as I’ve mostly driven old Toyotas without any luxuries, and I wanted something that would handle on twisty roads. I was looking at FD3S RX-7s, E36 BMWs, Porsche Boxsters and RX-8s. It came down to a Porsche Boxster or an RX-8, which won out because they are cheaper, and the wife said she wouldn’t be seen in a Boxster – fair enough, I s’pose!
“I had been scouring Gumtree for some time to find an RX-8 with a blown engine that wasn’t too rough in the body and interior, when I found this car, an auto with under 80,000km. I then bought a complete, but smashed, VE SS-V as a donor car and sold off all the bits I didn’t need to make back some money.”
As with many late-model Japanese cars, there is plenty of aftermarket support for the RX-8; however at the time Kevin undertook his engine swap there was a lot less around for him to simply buy and bolt in.
“I bought the engine crossmember from Racefab in NZ,” he explains. “At the time they only made an engine crossmember to suit the swap, so I made my own transmission member. They do now make a full kit with headers, tailshaft, crossmembers, the lot.”
Kevin used the VE’s stock L98 six-litre and T56 six-speed transmission package, with a Tilton clutch master cylinder added in, and got a custom tailshaft made to suit. A fifth-generation Camaro sump went on the bottom of the motor, filled with an Improved Racing baffle to stop oil surge, while the air filter was relocated to where the stock oil cooler lived in the front bar. He also added a pair of Hooker headers.
While all that might sound simple, there were plenty of headaches just fitting the motor and transmission into the Mazda.
“Mounting the remote shifter was punishing; then there was moving the front sway-bar so that it worked while not hitting anything, and mounting the gearbox,” Kev says. “RX-8s have no gearbox crossmember from the factory; they use a sort of torque arm called a ‘powerplant frame’, or PPF.
“My first go at a PPF delete ended in a snapped upper diff support and axle. I ran a custom diff support/PPF for a year but, while chasing a driveline vibration, I went back to a stand-alone diff brace from Racefab.
“There were clearance issues everywhere, and lots of things have been moved: the ABS module; brake lines; rearmost coil on the driver’s side; the a/c compressor fouled the engine mount; cylinder heads fouled the body seam at the firewall; the harmonic balancer fouled the radiator so that was moved forward six inches; and the Optima battery had to be moved to the boot.”
Kevin also had fun with the suspension, having to remove the RX-8’s standard electric steering rack in favour of an earlier FD3S RX-7 hydraulic steering set-up and custom tie-rods, while the diff was replaced with a rare 3.9-ratio LSD from an auto late-model RX-7. The struts were upgraded with Tein Flex coil-overs, and the stock rubber bushes got binned in favour of polyurethane Nolathane units.
Interestingly, Kevin’s LS RX-8 runs two computers, as he explains: “The car runs both the Holden ECU and the factory Mazda computer; the Holden ECU controls the engine and fuel pump, and the Mazda ECU runs all the gauges, air con, thermo fans, ABS and other cabin functions. The Mazda 13B crank trigger has been adapted to the V8 L98 harmonic balancer to provide an rpm signal to the Mazda ECU, and factory Mazda water and oil sensors have been connected to the engine to retain instrument cluster functionality. Both ECUs are in the factory ECU compartment along with fuse panel and relays.
“You need to keep the Mazda ECU to tie into the stock dash, but the engine runs stand-alone so it didn’t present any problems tuning it,” he continues. “The good thing is a VE SS is almost the same as a Camaro so you can get wiring diagrams off the internet and, as I was just using the engine wiring as a stand-alone, it made it so much easier.”
Even though it has more than 4.5 times greater capacity, Kevin says he didn’t have any problems making the Mazda legal. “The engineer picked me up on a couple of small issues like my charcoal canister sitting near my diff mount, but apart from that it didn’t have any problems,” he says.
While it has been a killer commuter, Kevin has put the LSRX-8 up for sale to concentrate on property for a while, although he won’t be abandoning the LS family just yet – his new daily is an LS1-powered Mitsubishi L300 van!
Kevin Jensen - 2003 Mazda RX-8
Type: Gen IV L98
Capacity: 364ci (6.0L)
Sump: Camaro, Improved Racing baffle
Exhaust: Hooker headers, twin 2.5in system
Gearbox: Tremec T56 six-speed manual
Diff: FD3S RX-7 IRS diff centre, 3.9 gears, Torsen LSD
Tailshaft: Custom billet adapter
Springs: Tein Flex coil-overs (f & r)
Brakes: Factory discs (f & r)
Rims: Enkei RPF1 18x9.5 (f & r)
Rubber: Federal 595RS-R (f & r)
Electrical help from Carl’s Auto Electrics; engine crossmember and diff brace from Racefab in NZ; MAF-less tune from B&T Automotive, Ingleburn; detailing by CAD Automotive Paint Correction; engineering and consulting by Greg South from G-Force Automotive; machining and welding help from my father-in-law; thanks to my wife for supporting my hobby