Driving a V6-powered Mazda MX-5 Rocketeer

How ideal becomes clearer when you learn that the V6, with its aluminium block and heads, weighs much the same as the original iron-block Mazda motor. And with a suitable adapter plate, designed by Southey, it mates to the original Mazda gearbox, which is well able to take the extra torque. The original final drive is also retained, as are the original springs and dampers.

So what does change in the Mazda beyond its beating heart? Most significantly, the front subframe. The standard item leaves no room for the V6’s exhaust manifolds, so Southey has designed a new one with space where required but strength retained. It’s not on our one-off prototype, which uses a modified tubular item for V8 conversions, but it will be part of the Rocketeer kit that Southey plans to sell at £5995 plus VAT. To that, you must add the engine itself, readily available second-hand for a few hundred pounds, plus a second MX-5 1.8 throttle body and idle control valve. Or two of each if your starting point is an early 1.6.

That sounds like a lot of money to shower on an old Mazda, but it makes sense when we look at what’s in the kit. First, though, what is a Jaguar V6-powered MX-5 really like? And would you want one?

Your resistance will weaken as soon as the engine catches. It blips keenly, its exhaust note a brassy blare with a crackling-crisp edge. This prototype has the six-speed gearbox that was optional in some early MX-5s, its shift less snickety than the five-speeder but the ratios closer. It’s not necessary with the V6’s torque, but it adds to the sense of near-continuous thrust.

There’s plenty of that, with rich pull from low revs right up to the limiter, all in a light car that seems to have very little inertia. This prototype is running on six small throttle bodies, whose intakes sit very close to the bonnet’s underside, a breathing restriction that flattens the pace after 6000rpm or so, but the Rocketeer kit will include a pair of proper carbonfibre plenums, fed by those MX-5 1.8 throttle bodies, and it should rev to the heavens.

Even as it is, the Rocketeer feels Porsche Cayman quick, it sounds fantastic and its chassis and suspension cope fine. There’s loads of grip, helped by 195/50 R15 Toyo Proxes T1-R tyres on wider Rota wheels, and great scope for steering ultra-accurately on the throttle in a way that a turbo conversion, or a nose-heavy V8, might not. The tail powerslides on an instant whim should the road be slippery, but it’s just as easily brought back into line. It’s a complete dynamic delight, and all the better for retaining the road feel that the standard, supple suspension offers.

So what do you get for your money? You get the subframe, a plug-and-play engine loom and ECU compatible with all the MX-5’s electrics, a twin-pipe exhaust system including manifolds, the flywheel and sump (both fully machined, bespoke items), the adapter plate, an uprated clutch, the carbonfibre plenum chambers, an electric water pump and all the hoses, filters, brackets and fasteners needed. Plus instructions, of course. The kit is suitable for Mk2s as well as Mk1s, and a weekend or two should see the transplant completed.