Today’s modern world is one that seems to keep serving up oddities, irregularities and enigmas. Those little moments when you stop and think to yourself, “that’s just not right”. Everything from George Bush getting a second term in office and cheese in a can, to that suspiciously masculine-looking woman down on the corner of your street. All these things seem to defy nature, going against the grain much like Jason Knight’s 1985 Mazda RX-7.
This particular Series Four RX-7 is Mazda’s popular mid-80s incarnation of its much celebrated line of iconic rotary-powered sports coupes. Rolling out of Mazda’s Hiroshima factory back in 1985, the car packed a turbocharged 13B rotary engine, making a then respectable 141kW at the flywheel. This was how it stayed until late 1999, when a young Jason Knight purchased the car. Of course, it kept true to rotary form, so after owning the high-revving ’80s icon for a mere two hours, Jason managed to pop the motor. Not impressed with the prospect of constant reliability issues, he knew the Jap motor had to go.
Luckily for this little rice rocket, its new owner had a bit of a thing for American iron after owning a few V8-powered machines in the past, including a Datsun 1200 coupe housing a 327 (5359cc) Chev. That motor was chosen as the new power plant for the fortunate Mazda. Once the ’69 Camaro-sourced engine was out of the Datsun and on the floor, Jason decided to crack it open and got to work on the internals for a mild overhaul.
The Chevy motor sports a four-bolt main block, helping to strengthen the bottom end. Coupled to mildly ported fuelie heads, a steel crank, standard rods, 30-over flat-top pistons and a Crower hydraulic cam, the small block motor was ready to get some tyres turning and some rubber burning, the latter process being one that Jason was well acquainted with. Unhappy with the amount of air the standard intake system provided, Jason invested in an Edelbrock dual plane Performer intake manifold, a 600cfm Holley carburettor and a Mr Gasket bug catcher rearing its polished head high above the original lines of the car via a hole cut in the standard bonnet.
With these modifications came the need for more fuel to match the increased airflow. This was answered by a mechanical high volume fuel pump providing the Holley carb with enough fuel to feed the fire and sparked by the stock distributor with an electronic ignition kit.
Once the engine was prepped and ready to go, Jason and his father, Dave, got to work fabricating custom mounts in preparation for the small block. Then Jason stripped the shell and took it to Johnsonville Panel Beaters, where his friend Cliff Blackwood straightened and erased over a decade of wear and tear. Once every panel on the car was as straight as Crocodile Dundee at a knife convention, Jason enlisted the help of another friend, Wayne Smith, who coated the Japanese coupe’s shell in a lusty Ford Mustang Purple. Although the new hue was a treat to the eye, it just wasn’t enough for Jason, so he had Wayne spray an inferno of hot rod-style flames across the front end of the car as well. Once the paint had dried and the car was back at the workshop, Jason and friends pulled out the engine hoist and got to work dumping the hefty 327 Chev into the freshly painted engine bay.
Jason then got to work installing the tight-fitting block hugger exhaust headers with three-inch dump pipes. These cram the exhaust gasses through a pair of 2.25-inch twin pipes and into the atmosphere via a pair of three-inch tips at the rear of the vehicle. With the engine finished, it became apparent that the standard Mazda radiator just wouldn’t be up to the task of keeping everything at an acceptable temperature during the odd heavy-booted jaunt through the hills. This is where Toyota came to the party, providing more-than-adequate cooling via a Hilux radiator and twin electric fans.
Also helping to keep things under control and counteract oil surge is a custom-made alloy oil catch can. Now that the little Mazda had its much bigger heart bolted in and ready to go, Jason needed to find a way to get all that new-found torque to the ground. Obviously, the standard RX-7 gearbox was about as useful as tits on a bull, so salvation was found in the form of a Z28 Camaro five-speed manual unit. This now gets its power through an aftermarket, heavy-duty clutch plate and steel flywheel. Once the grunt has made its way through the gearbox, it is transferred to a XJ6 Jaguar diff head via a custom-made drive shaft. The differential, which is mated to the stock Mazda independent rear end, drives the 17-inch chrome Stalker rims, using a pair of shortened heavy duty axles mated to RX-7 CVs.
The 17-inch Stalker wheels, manufactured by Advanti, are wrapped in ultra-low profile 225/40-17 rubber on the back, and 215/40-17 rubber on the front. These give the car a simple, yet very effective upgrade in the looks department, not to mention adding to the now very potent little coupe’s handling abilities.
Keep It Real
Speaking of handling, Jason had a fair idea that the new, much heavier donk up front was going to make this a completely different car from what he had previously experienced. As a result, some upgrades were definitely in order if he ever planned to put his foot down without ploughing off the road and turning up uninvited in some poor bastard’s living room during Coronation Street.
Jason binned the aging standard gear and invested in a set of adjustable KYB shocks and King Springs super low coils that brought the car a whole lot closer to earth, providing reduced body roll and a lower centre of gravity.
With much of the project nearing completion, Jason got sensible and turned his attention to the braking department. Since the RX-7 comes standard with very competent disc brakes front and rear, all Jason had to do was rebuild the four-pot callipers with a mix of new and reconditioned parts. Once that was done, all that was left was to install a set of Metal King brake pads to provide a more than adequate level of braking power when the need to stop in a hurry arose.
Finally, after a fair whack of money and not to mention a whole lot of effort, the little Mazda with a big heart was ready to attack the black stuff. Once everything was certified and Jason had added a sports steering wheel, gear knob and 127mm tachometer to the otherwise standard interior, the new and much improved RX-7 hit the streets.
This happened four years ago now, and since then the car has spent its time blasting through the hills around Wellington, performing the occasional tyre-shredding burnout and getting Jason to his job as a mechanic every single day. You can plainly see the car is still in mint condition. It seems Jason takes care of it in much the same way as Tiger Woods plays golf — very well indeed.
While it easily falls into the “that’s just not right” bracket, this particular muscle-spec Mazda could be a big improvement over the factory item. Not that the rotary fraternity are ever likely to admit it.
1985 Mazda RX-7
ENGINE: Rebuilt, fully balanced 327 (5359cc) small block Chevy (ex ’69 Camaro), four-bolt main, steel crank, standard rods, 30-over flat top pistons, Crower hydraulic cam, ported Fuelie heads, dual plane Edelbrock Performer intake manifold, 600cfm Holley carburettor, Mr Gasket bug catcher, mechanical high-volume fuel pump, electronic ignition kit, block hugger headers, twin pipe exhaust system, Toyota Hilux radiator with twin electric fans
DRIVELINE: ’84 Z28 Camaro T5 manual gearbox, heavy-duty clutch, steel flywheel, Jaguar XJ6 differential, shortened heavy-duty axles
SUSPENSION: KYB adjustable shocks and King Springs
BRAKES: Rebuilt standard disc brakes and Metal King pads
WHEELS/TYRES: 17×8-inch rear, 17×7-inch front chrome TSW Stalkers, 225/40-17 rear tyres, 215/40-17 front tyres
EXTERIOR: MazdaSpeed rear wing, Ford Mustang Purple paint, custom flames
INTERIOR: Sportline steering wheel, custom gear stick, 127mm tachometer with shift light
PERFORMANCE: Not tested
Previously owned cars: ’67 Chevy Impala with a 400 (6555cc) small block (currently owned), XD Falcon with a 302 (4949cc), XF Falcon panel van with a 302, Datsun 1200 coupe with a 327 (5359cc) Chev
Dream car: 1959 Chevy sports coupe
Why did you build this car? The standard 13B rotary blew up after owning the car for two hours. I still had the 327 lying around from my Datsun and this is where it ended up
Build time: Two years
Length of ownership: Six years
Thanks to: My fiancee Kara for being so patient about the amount of time I spend in the workshop, my father Dave Knight, Wayne and Cliff for the panel and paint, Seaview Engineering, Motor Doctors where I now work and which I use as a garage.