Nissan RB30 engine: Your guide to the petrol six-cylinder motor

Nissan’s RB30, 3.0-litre in-line six-cylinder engine has gone down in history as one of the best straight sixes of all time. Part of the RB family of inline engines (built in Japan from 1985 to 1991) that ranged from two to three litres, the RB30 in various guises has powered Australian cars ranging from all-wheel-drive supercars to butch off-roaders and every kind of taxi, police car and family wheels in between.

Interestingly - and with one notable exception - Australia only ever saw the RB engine in 3.0L form. But that was okay by a generation of Australians who truly believed that there was no substitute for cubic inches. And we’re kind of on their side in this case.

The Nissan RB30 was first seen in Australia, ironically enough, in a Holden. The date was March 1986 and the reason was one of engineering expediency. That was the year that unleaded petrol (ULP) became mandatory in Australia and it was painfully obvious to Holden’s engineers that the old faithful 3.3-litre Holden six - that had been powering Aussie family cars since the EH model of 1964 - simply wasn’t going to make the transition to ULP. So, Holden went shopping and bought a batch of Nissan-built RB30s for the new VL Commodore (and Berlina and Calais) for 1986.

Nissan’s own family car, the locally-made Skyline, meanwhile, followed the Commodore just three months later, complete with exactly the same engine, right down to the number of KiloWatts under the bonnet (114kW, to be precise). With either a five-speed manual or a newfangled electronically-controlled four-speed automatic, the Skyline was a good performer, while the addition of the RB30 absolutely transformed the Commodore from a plodder to some kind of thoroughbred.

Those were the mainstream applications for the engine, but there were a bunch of lower-volume uses for it that helped create the legend. Those started in August 1986 with the Commodore Turbo. Through some strange commercial arrangement with Nissan concerning the supply of the engines, only Holden was able to sell the turbocharged version of the RB30 in Australia. But what a thing to have!

The naturally aspirated RB30 produced 114kW/247Nm. (image credit: Haltech Support Center)

With a lower compression bottom end, a Garrett T3 turbo unit and 250cc fuel-injectors, the VL Turbo cranked out 150kW of power and 296Nm. In an age where a Hyundai hot-hatch makes 202kW and 353NM, those numbers sound a bit weedy. But you have to put the VL Turbo into context; it was a very powerful car for the day; and, at 1350kg or so, it was a full 150kg lighter than the Hyundai i30 N we’re comparing it to (and despite being a full-sized family car, the Holden was less than two centimetres longer in the wheelbase than the Hyundai). And compared with even the Commodore V8 of the day, the Turbo was the undisputed performance king.

Although it couldn’t get its hands on the turbocharged RB30, Nissan still turned the engine into a performance unit through its Nissan Special Vehicles Division. It produced a limited run of Skylines (in all white, right down to the wheel rims) and with a different camshaft and exhaust manifold, got the RB producing 130kW. That Series 1 car sold between mid-1988 and mid-1989 before SVD backed up with a Series 2 car (in red this time) which was on sale until 1991 and produced an extra 10kW.

With a Garrett T3 turbo and 250cc fuel-injectors, the RB30DET pushed out 150kW/296Nm. (image credit: Haltech Support Center)

With prices of its Patrol four-wheel-drive being driven up further and further thanks to exchange rate fluctuations, Nissan engineered a budget-oriented version of the off-roader with a carburetted, 100kW version of the RB30. Dubbed the ST30, the vehicle sounds pretty left-field now, but was marketed at a time before the popularity of diesel engines, so even in its manual-only guise, it wasn’t as loopy as it sounds now. Performance in the 2.3-tonne Patrol was, however, decidedly on the mild side.

The RB30 in-line six found its way into the Patrol to create the ST30 variant.

The ultimate form of the RB in Australia? That’s an easy one: In 1991, we received a batch of Nissan’s celebrated Skyline GT-R. Known to the faithful as Godzilla, the GT-R in R32 form used a 2.6-litre version of the RB (RB26DETT) along with sequential turbochargers and a DOHC cylinder head for a claimed output of 206kW. But that number was probably hugely conservative (Japanese car-makers had an agreement with the government at that time not to exceed 206kW on a production car) and was almost certainly closer to 260kW. It would be Australia’s last officially-imported taste of the GT-R legend until the R35 model arrived in 2009, by which time Nissan had moved to a V6 engine layout.

Why so special?

While the road-going R31 used the RB30, the Group A racer used a turbo RB20 engine instead.

So what was it that made the RB30 so special? From some angles, the engine was actually nothing special. It used a cast-iron block and an alloy head which was far from unusual, and in everything but the Nissan GT-R, the engine was a single overhead camshaft design with just two valves per cylinder. And in other ways, it was absolutely antiquated. The basic architecture, the bore-stroke relationship, for instance, was very closely related to the old L-series Nissan six-cylinder engines; the units that powered cars like the Datsun 240Z for instance.

But what made the RB30 great was almost certainly the quality of its design and engineering. It was smooth, very tuneable, able to cope with the coming turbo-era and drove extremely well compared with what else was around in Australia at the time. In power and torque terms it was miles ahead of the Holden and Ford offerings of just a few years earlier, and it trumped those engines for fuel economy and smoothness into the bargain. Throw in the four-speed automatic - which wouldn’t arrive at Ford until the end of 1989 - and the RB30 package was a winner.

The other element that stamps the unit as a bit special was its reliability. In fact, it would comfortably outlive local sixes, and plenty of RB30 owners have reported clocking up more than 400,000km without major hassles. In fact, the basic engine is so tough that Nissan actually converted it to diesel to create the RD28 that powered some Patrol four-wheel-drives and others. That speaks volumes for the design’s inherent robustness.

The only vaguely common fault that has come to light over the years is not really a flaw in the engine’s design, but rather a problem with its installation in the Holden Commodore. The sloping nose of the VL Commodore dictated a radiator with a header tank lower than the highest point in the cooling system’s water jacket. Which meant that if you didn’t bleed all the air out of the system when refilling the radiator, you could end up with an air-bubble in the cylinder head which would create a hot spot and potentially damage the engine. The Nissan Skyline, with its rather more upright front, did not suffer the same dramas.

Beyond that, the combination of a cast-iron exhaust manifold and an alloy head (and the differing rates of thermal expansion of those two metals) can cause the manifold to become loose and the gasket to blow. But the RB30 is hardly on its own in that department.

The fact is that the engine is so beloved by enthusiasts that Nissan last year announced that the RB26DETT version of the unit will go back into production as part of its Nismo Heritage Parts program. The program was established in 1997 to enable owners and restorers to source impossible-to-find parts, including, in this case, a whole engine or parts thereof.

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