RB26 or 2JZ? Which is the best six-cylinder import performance engine of all time? Nissan fans will tell you about the legendary breathing ability of the RB cylinder head and the incredible 10,000-plus RPM potential of its short-stroke design. Toyota 2JZ fans brag about the displacement advantage that the longer-stoke 2JZ delivers. What if a RB owner could have the best of both worlds? We are talking about a 3.0-liter engine with the great breathing ability and race-bred design of the RB engine. For the true maniacs looking to build an RB with the same displacement as a 2JZ, OS Giken has the answer. The OS Giken RB30 engine package allows an RB26 owner to increase the stroke and the displacement to 3.0-liters.
Text & Photos by Richard Fong
The 3.0-Liter Conversion
OS Giken’s solution to a bigger RB begins with an RB26 cylinder block. OS Giken machines and sleeves the block before fitting the block with a special deck plate. This process allows the longer-stroke crankshaft to be used while still maintaining a desirable ratio between the length of connecting rods and the length of the stroke. OS Giken supplies a billet crankshaft with an 86mm stroke (factory RB26 stroke is just 73.7mm). This long-stroke crank teams with OS Giken custom-length forged H-beam connecting rods and custom 86mm aluminum pistons. This bore-and- stroke combination provide the RB engine with the same displacement as the Toyota 2JZ-GTE engine (2,998cc). Since the deck height is increased with the OS Giken system, a special timing belt and tensioner kit is supplied. High strength head studs and main studs are also included to keep the components in the right place. Main bearings, rod bearings and a metal head gasket are also included in the system. A custom clutch system offered by OS Giken is required to work with the 8-bolt flanged crankshaft.
Beyond the Block
So what chassis would be the ideal candidate to receive monster engine like the OS Giken RB30? In the case of OS Giken customer, Mr. Kubo, his focus was to build a racecar that would deliver single-digit 0-to-400m times. His weapon of choice was the ever-capable R32 Nissan Skyline GT-R. With the RB30 shortblock as the foundation, Kubo decided to address the cylinder head. A complete TOMEI POWERED valvetrain, including valves, springs and retainers, replaced the factory equipment before the head was mated to the block. A 1.2mm OS Giken head gasket ensures a good seal. High-lift TOMEI POWERED 280-degree camshafts actuate the valvetrain and facilitate greater airflow in and out of the cylinders.
To give the heavy-breathing RB30 engine the boost it needs to make power, an HKS twin-turbo exhaust manifold was selected to channel gases from the exhaust ports into the turbine inlets of the GT3240 turbochargers. From the turbine outlets, spent gases flow to the atmosphere through a GReddy stainless-steel exhaust system. From the compressors, custom intercooler piping channels charge air to the massive GReddy front- mount intercooler. Once chilled, the aircharge flows to the polished GReddy intake manifold. A six-pack of SARD 1,000 cc/min fuel injectors and six factory 440cc/min injectors receive 103- octane pump gas from a triad of Bosch 044 fuel pumps. Relying on an HKS EVC boost controller for consistent 32 psi boost pressures, an HKS F-CON VPRO engine management system regulates fuel delivery and commands spark energy to spin the wheels to the tune of 1,188 wheel horsepower and 795 lb-ft of torque.