The RB engine platform, particularly the RB26DETT and RB25DET, holds an almost legendary status in the tuning world. Swapping one of these inline-six powerhouses into a 240SX, Skyline, or Silvia is a proven path to serious horsepower. The 700 horsepower mark is a significant milestone that separates well-researched builds from unreliable projects. Reaching this number requires a systematic approach to hardware selection, fuel delivery, and engine management. This guide outlines the specific components and tuning strategies required to achieve a reliable and streetable 700 hp RB swap.

Evaluating the Foundation: Choosing the Right RB

Not every RB engine reacts the same way to modifications, so understanding the starting point is critical for budgeting and part selection.

  • RB20DET: The 2.0-liter is the smallest of the family. Its smaller bore and weak factory rods make it a poor choice for a 700 hp goal without extensive machine work and a full rotating assembly replacement.
  • RB25DET (Series 1 & 2): The 2.5-liter provides better torque and a strong iron block. However, the factory crankshaft is not forged, and the rods are pressed. For 700 hp, a fully forged rotating assembly is required.
  • RB25DET NEO: This engine offers improved cylinder head flow and variable cam timing (VCT). It is an excellent starting point but still requires a forged crank, rods, and pistons to handle the stress of 700 hp.
  • RB26DETT: The factory forged steel crank, 6-bolt main caps, and billet oil pump gears make this the strongest stock foundation. While the pistons and rods are still cast and should be replaced, the bottom end architecture is superior for high horsepower builds.

The Bottom End: Building a Reliable Foundation

700 hp places immense stress on the rotating assembly. The factory cast pistons and pressed rods are not designed for this power level. A fully forged rotating assembly is the only path to long-term reliability.

Connecting Rods and Pistons

Select a name-brand forged rod from Manley, Eagle, or Carrillo. For pistons, CP-Carrillo, Wiseco, and JE Pistons offer off-the-shelf options for RB swaps. A compression ratio of 8.5:1 to 9.0:1 is a safe range, allowing for high boost on pump gas or E85.

Crankshaft and Bearings

The RB26 factory crank is forged and is generally sufficient for 700 hp if properly prepared with oiling modifications and chamfered oil holes. For the RB25, an aftermarket forged crank from Spool or Collins Imports is a wise investment. Upgrade to ACL Race or King XP bearings and have the clearances verified by a professional machinist.

Oil Pump and Girdle

The factory oil pump gears are a known weak point in high-RPM RB builds. A billet oil pump gear set from Tomei or Jun is essential. Installing a crank collar eliminates the risk of the oil pump drive failing. A modified oil pan with baffles and a windage tray ensures consistent oil pressure during hard cornering and acceleration.

Cylinder Head and Valvetrain

The RB cylinder head responds well to porting and larger cams. For 700 hp, the goal is to move the powerband to match the turbocharger's efficient range without losing low-end response.

Valve Springs and Retainers

High boost and high RPM require upgraded valve springs. Dual springs with titanium retainers prevent valve float and keep the valvetrain stable at 7500+ RPM. Companies like Ferrea and Supertech offer drop-in solutions.

Camshafts

Cam selection depends on the turbo. For a GT35 or larger frame, a 260/260 or 264/264 degree cam with 9.15mm lift (Tomei Poncam or Kelford 196-B) provides an excellent balance of power and drivability. For larger turbos in the GT40 range, a 270/270 or 272/272 profile helps shift the powerband higher.

Head Studs and Gasket

Boost pressure over 20 psi will lift the stock head studs. Upgrade to ARP L19 or 2000 series head studs. A multi-layer steel (MLS) head gasket from Cometic or Tomei is required to seal the combustion chamber reliably. Proper surface preparation of the block and head is essential for the MLS gasket to seal.

Turbocharging: The Power Source

700 hp requires a substantial amount of airflow. A turbo in the GT35, GT40, or BorgWarner S300/S400 frame size is necessary.

Turbo Selection

Popular 700 hp turbochargers include:

  • Garrett G35-1050 (dual ball bearing, billet wheel)
  • BorgWarner S366 SX-E
  • Precision 6266 Gen 2
  • Comp Turbo CT4-6262

These turbos support 700-750 hp while remaining relatively responsive on a 2.5L or 2.6L engine. Use a turbo map to verify the compressor wheel is efficient at your target boost level. Expect to run between 25 and 30 psi to reach the 700 hp threshold.

Manifolds and Wastegates

A top-mount exhaust manifold is standard for full-size turbos. A twin-scroll manifold combined with a divided housing (T4 Twin Scroll) significantly reduces spool time. You will need a 44mm or 60mm external wastegate from Tial or Turbosmart to regulate boost pressure precisely. A boost controller with gear-based duty cycles is recommended for managing traction in lower gears.

Fuel System: Managing the Flow

A 700 hp RB needs a comprehensive fuel system overhaul. The stock feed lines, pump, and injectors cannot meet the demands of this power level.

Fuel Pump and Lines

A single Walbro 450 or AEM 380 is marginal for 700 hp on pump gas and insufficient on E85. Run either a surge tank system with twin Walbro 450s or a single high-flow brushless pump from Radium or Aeromotive. Feed the system with -8AN line and return with -6AN. AN fittings and PTFE-lined hose are recommended for compatibility with ethanol.

Injectors

High-impedance injectors from Injector Dynamics (ID1300 or ID1700) or Bosch are the industry standard. They provide linear flow characteristics and consistent spray patterns, which make tuning easier and safer. For E85, 1300cc injectors are the minimum.

Fuel Management Unit

A boost-referenced fuel pressure regulator from Fuelab or Aeromotive is needed to maintain a consistent differential pressure across the injectors. This ensures predictable fuel delivery as manifold pressure changes. A return-style fuel system is non-negotiable for this power level.

Engine Management and Tuning

Dialing in a 700 hp RB requires a sophisticated engine control unit (ECU). Factory ECUs cannot handle the input from modern sensors or control large injectors effectively.

Standalone ECU Selection

Standalone systems from Haltech, Link ECU, and AEM are optimized for the RB architecture. The Haltech Elite 2500 or Link Fury offer features like on-board logging, Flex Fuel support, and advanced boost control. A plug-and-play adapter harness is available for most chassis, reducing installation time.

Professional Tuning

Even the best parts will fail with a poor tune. Invest in a professional dyno tune from a technician experienced with RB engines and standalone ECUs. The tuner will optimize fuel maps, ignition timing, and the boost curve to maximize power while maintaining safe exhaust gas temperatures and minimizing knock.

Sensors and Logging

Accurate sensor data is required for tuning. Upgrade to a GM-style IAT sensor, a 3 or 4 bar MAP sensor, and a wideband O2 sensor. A dash logger like the Haltech IQ3 or AEM CD-7 allows the driver to monitor critical parameters and detect issues before they cause damage.

Induction and Exhaust

To make 700 hp, the engine must breathe efficiently.

Intake Manifold

The stock RB intake manifolds are restrictive at high RPM. A plenum-style intake manifold from Plazmaman, GReddy, or Hypertune improves flow distribution and increases volume. A large throttle body measuring 90mm to 100mm is required to feed the plenum adequately.

Exhaust System

A full 3.5-inch or 4-inch exhaust system is needed to keep exhaust velocity high and back pressure low. A high-flow downpipe matched to the turbocharger outlet is the first step. A quality exhaust system from HKS, GReddy, or a custom mandrel-bent setup will support the power goal without excessive restriction.

Cooling System: Managing Heat

700 hp generates a tremendous amount of heat. If the cooling system is neglected, the engine will overheat, leading to detonation and failure.

Radiator and Ducting

A high-capacity aluminum radiator from Koyo or Mishimoto is a necessary upgrade. Proper ducting and shrouding are just as important as the radiator itself. Ensure air is forced through the core, not around it. Electric fans with a thermostatic switch or ECU control help manage temperatures in traffic.

Oil Cooling

The RB's oil system works hard at high RPM. A large air-to-oil cooler from Setrab or Earl's with -10AN lines is essential to keep oil temperatures below 230°F under sustained load. A thermostatic sandwich plate is recommended to prevent over-cooling during warm-up.

Intercooler

A large front-mount intercooler with a Garrett or PWR core is required to cool the compressed air from the turbo. Aim for a core that is 3.5 to 4 inches thick with efficient bar-and-plate construction and cast end tanks. Pressure drop across the core should be minimal.

Drivetrain: Transmitting the Power

700 hp will destroy weak drivetrain components. The transmission, clutch, axles, and differential must be built to handle the torque.

Transmission Options

The stock RB25 or RB26 transmission (FS5R30A) is marginal at 500 hp and won't last at 700 hp. Reliable options include:

  • CD009 Conversion: Nissan 350Z/Infiniti G35 transmissions are strong and relatively affordable. Requires a bellhousing adapter from companies like Collins or Xcessive.
  • Getrag V160/V161: Found in the Toyota Supra, these are extremely strong but expensive to source and adapt.
  • R33 Skyline GTR Getrag: A direct fit for RB engines and capable of holding over 700 hp. This is the most straightforward OEM+ upgrade.

Clutch Assembly

A twin-disc clutch from South Bend, Competition Clutch, or OS Giken is required to handle the torque without slipping. Look for a sprung hub design if you want to maintain some street manners. The clutch should be rated for at least 20-30% more torque than the engine produces to provide a safety margin.

Axles and Differential

The stock axles in most swap chassis will snap under hard launches. Upgraded axles from The Driveshaft Shop or DSS are a must for any 700 hp car. The differential should be rebuilt with a stronger LSD unit from OS Giken or Nismo, and billet bearing caps should be installed to prevent the case from flexing.

Chassis and Safety

Handling 700 hp requires a stable chassis and effective brakes.

Brakes

Upgrading the braking system is a safety requirement. A Z32 300ZX brake upgrade is a common budget-friendly option that provides four-piston front calipers. For serious track use, a big brake kit from StopTech or Brembo with larger rotors provides the stopping power needed to match the acceleration.

Suspension

Quality coilovers from KW, Ohlins, or BC Racing and adjustable suspension arms allow for proper alignment and weight transfer management. This is critical for getting the power to the ground. Upgraded sway bars and solid subframe bushings improve chassis response and stability.

Tuning Summary and Common Pitfalls

Reaching 700 hp is about the details. Here are the most common mistakes builders make:

  • Inadequate Fuel System: Assuming a single Walbro 450 is enough for E85 at 700 hp. It is not. Plan for a dual pump or brushless setup from the start.
  • Stock Head Studs: OEM studs will stretch under high boost, lifting the head and blowing the gasket. ARP studs are a relatively cheap insurance policy.
  • Ignoring Heat Soak: Failing to duct the intercooler or radiator leads to high intake air temperatures and lost power.
  • Cheap Engine Management: Trying to make 700 hp on a stock ECU with a piggyback system. A standalone ECU is required for this power level.
  • Drivetrain Neglect: Building a 700 hp engine and bolting it to a tired stock transmission is a recipe for disaster. Upgrade the drivetrain to match the power output.

A safe, conservative tune that prioritizes reliability over peak power numbers will provide a much better ownership experience. Focus on proper lambda values, conservative ignition timing, and robust boost control rather than chasing dyno records.

Putting It All Together

Building a 700 horsepower RB swap is a substantial undertaking that requires careful component selection and precise execution. By investing in a forged bottom end, a properly sized turbo system, a comprehensive fuel setup, and a standalone ECU, you can achieve a powerful and reliable vehicle. The RB platform is proven, the parts are widely available, and the community knowledge is extensive. With the right preparation and a realistic budget, 700 hp is an achievable and rewarding milestone for any dedicated enthusiast.