Choosing the Right Foundation: The RB20DET

The Nissan RB20DET is a 2.0‑liter turbocharged inline‑six that has earned a loyal following among performance enthusiasts. Its cast‑iron block, aluminum cylinder head, and factory turbocharging make it an ideal candidate for a budget‑friendly 250‑horsepower build. With the right upgrades — especially in the valvetrain — this engine can deliver reliable, daily‑driveable power well beyond its stock rating of around 210 hp (in some markets).

Before you begin, understand exactly what you’re working with. The stock RB20DET came in several variants (R31, R32, R33 Skyline, Cefiro, Laurel), but all share a similar architecture. The key components you’ll interact with during this installation are:

  • Engine block – cast iron, closed deck, capable of handling moderate boost
  • Cylinder head – 24‑valve, shim‑over‑bucket design (early models) or shim‑under‑bucket (later models)
  • Forged connecting rods – stock rods are adequate for 250 hp, but watch for rod bolts
  • Cast pistons – acceptable at this power level, but a fresh set of OEM or aftermarket pistons is recommended if the engine is apart
  • Turbocharger – typically a Garrett T3 flange with a small frame unit; you’ll want to upgrade the turbo or at minimum the actuator and wastegate for 250 hp
  • Fuel system – top‑feed injectors, side‑feed on some models; larger injectors and a fuel pressure regulator are advised

For this guide, we assume you’re starting with a complete, running RB20DET (or a long‑block that has been rebuilt). If your engine is already out of the car, you can skip the removal steps and jump directly to the preparation phase.

Gathering Your Tools and Parts

A project like this requires preparation. Don’t start pulling bolts until you have everything within arm’s reach. The following list covers the essential tools and the critical parts you’ll need for the 250‑hp build.

Tools

  • 3/8‑ and 1/2‑inch drive socket sets (metric, 8‑19 mm)
  • Torque wrench (0‑150 ft‑lb range)
  • Engine hoist (2‑ton capacity minimum) and leveller
  • Engine stand
  • Pliers, screwdrivers, wrenches (combination and flare‑nut for fuel lines)
  • Pry bar and soft‑faced mallet
  • Plastigauge for bearing clearance checks
  • Feeler gauges
  • Vacuum/pressure gauge
  • Multimeter

Parts and Consumables

  • Ferrea valves – we’ll use the F1705 (intake) and F1706 (exhaust) stainless steel valves, which feature improved alloy and swirl‑polished stems for better flow and durability. They are a direct replacement for the stock 31 mm intake / 27.5 mm exhaust valves.
  • Valve stem seals – high‑temp Viton (order a set specific to RB20DET)
  • Head gasket – metal (Multi‑Layer Steel) for boosted applications, e.g., Cometic or Tomei
  • Head studs – ARP 2000 or L19, crucial for clamping force
  • Gasket set – full engine gasket set (felpro or OEM) including intake/exhaust gaskets
  • Timing belt and tensioner – always replace when the head is off
  • Oil and coolant – high‑zinc break‑in oil (e.g., Valvoline VR1 20W‑50), distilled water + coolant
  • Spark plugs – NGK BCPR7ES (gapped to 0.028‑0.032 inch for boost)
  • Injectors – 440 cc or larger (Bosch EV14 style recommended)
  • Fuel pump – Walbro 255 lph or equivalent
  • Boost controller – manual or electronic, to dial in 10‑12 psi

Step 1: Remove the Stock Engine

If your vehicle already has the RB20DET installed, you’ll need to extract it. If you’re swapping into a different chassis (e.g., an S13, S14, or R32), the removal process will be similar — just adapt the steps for your specific car.

Pre‑Disconnection

Disconnect the battery negative terminal. Drain the engine oil and coolant. Remove the radiator, intercooler piping, and air intake assembly. Label every electrical connector you unplug — take photos for reference. Remove the driveshaft (if RWD) and unbolt the transmission from the engine (support it with a jack).

Disconnecting Engine Attachments

  • Unplug the wiring harness at the main bulkhead connectors (engine side).
  • Disconnect fuel lines: supply and return (watch for residual pressure).
  • Detach heater hoses, upper and lower radiator hoses.
  • Remove the exhaust downpipe from the turbo (three bolts, often rusted — soak with penetrant).
  • Disconnect the accelerator cable, cruise control (if equipped), and any vacuum lines.

Lifting the Engine

Attach the engine hoist to the lifting brackets on the intake and exhaust sides of the head. Ensure the chain is secure and the leveller is balanced. Remove the engine mount nuts/bolts. Slowly lift the engine — check for any remaining cables or hoses. Once clear, roll the hoist away and set the engine on a stand.

Step 2: Prepare the RB20DET for 250 HP

With the engine on a stand, drain the remaining oil and remove the oil pan (so you can inspect the bottom end). Now you’ll focus on the cylinder head — the key to unlocking reliable power.

Remove the Cylinder Head

Remove the timing belt, camshaft pulleys, and camshafts (keep the shims or buckets in order). Unbolt the head in the reverse of the tightening sequence (typically starting from the outside). Lift the head off and set it on a clean workbench. Remove the stock valves, keepers, retainers, and springs.

Installing Ferrea Valves

Ferrea valves are a significant upgrade over OEM units: they’re made from a stronger stainless steel alloy (904L or similar) and feature a polished stem that reduces friction and heat. They also have a narrower stem diameter on some applications, which can improve airflow. For the RB20DET, you’ll order the direct‑fit Ferrea valves (part numbers F1705 intake, F1706 exhaust).

Installation steps:

  1. Clean the valve guides thoroughly. Check for wear — if the guides are loose, replace them (machine shop required).
  2. Apply assembly lube to the valve stems and guides. Insert each Ferrea valve into its respective guide.
  3. Install new Viton valve stem seals using a seal driver (do not hammer them — press evenly).
  4. Place the valve spring, retainer, and keepers. Use a valve spring compressor to compress the spring and seat the keepers. Ensure the keepers are fully seated.
  5. Repeat for all 24 valves.

Pro tip: Measure installed spring height. If you replaced springs (highly recommended for higher boost), verify that the spring pressure is within spec for the camshaft you’ll be using. Stock RB20 cams are fine for 250 hp, but aftermarket cams (e.g., HKS 256/264) would require stiffer springs. For this build, we’ll use the stock cams with new stock‑rate springs or mild upgrades (e.g., Ferrea S2000 springs).

Reassemble the Cylinder Head

Check that the valve stem heights are uniform. If they vary more than 0.005 inch, you may need different shims or a machine shop to grind the valve tips. Install the camshaft(s) with fresh assembly lube, and set the shim clearance to factory spec (typically 0.008‑0.013 inch for intake, 0.010‑0.015 inch for exhaust). Torque the cam caps to spec in the proper sequence.

Install a new metal head gasket (MLS) and ARP head studs. Follow the head stud manufacturer’s torque procedure — usually three stages: 30 ft‑lb, 60 ft‑lb, then a final 90‑100 ft‑lb (or a specific angle). Always re‑torque after one heat cycle.

Bottom End Inspection

At 250 hp, the stock RB20 bottom end is adequate if the engine is healthy. However, it’s wise to replace rod bolts with ARP rod bolts (the factory bolts are marginal). Clean the oil pan, replace the oil pump (Nissan recommends a new one at rebuild), and install a new rear main seal. If the engine has high miles, consider new piston rings and bearings — plastigauge the clearances.

Step 3: Install the Engine into the Vehicle

With the head assembled and the block prepped, mate the transmission to the engine (or install transmission separately). Use a new pilot bearing and throwout bearing. Attach the engine hoist again and carefully lower the engine into the engine bay.

Aligning Mounts

If you’re using the stock mounting brackets, they’ll align with the crossmember. For swaps, you may need aftermarket mounts (e.g., Nismo polyurethane). Ensure the engine sits level and the transmission mount aligns without stress. Do not tighten the mount bolts fully until the engine is sitting on its own weight.

Connect Ancillaries

Reattach the wiring harness, fuel lines, coolant hoses, and downpipe. Install the intercooler piping (upgraded to 2.5‑inch diameter recommended). Connect the throttle cable and all vacuum lines. Install the radiator, overflow tank, and electric fans. Fill with engine oil (break‑in oil) and coolant (distilled water + coolant mix).

Step 4: Tuning for 250 Horsepower

The Ferrea valves alone won’t add horsepower. They enable the engine to rev safely and support higher airflow. The real gains come from fuel and boost management.

Increase Fuel Flow

Install a Walbro 255 fuel pump (or equivalent). Replace the stock injectors with 440 cc or 550 cc units (check compatibility with your ECU). A rising‑rate fuel pressure regulator set to 43.5 psi base pressure (with vacuum off) will help. If you’re using an aftermarket ECU like a Nistune, Haltech, or Link, you can tune the fuel map precisely. For a piggyback (SAFC), you can adjust airflow readings — but a proper ECU tune is strongly recommended.

Raise Boost

Stock RB20 turbo (e.g., T3 .42) can be pushed to 10‑12 psi with a good intercooler and fuel system. That’s typically enough for 250 crank horsepower. Install a manual boost controller and set to 10 psi initially. Monitor knock via a detonation can or aftermarket knock gauge. If you want a bit more safety, upgrade to a hybrid turbo like a GT2560R — it spools quickly and flows enough for 280‑300 hp.

Ignition Tuning

Retard timing slightly at high boost (around 15‑20 degrees at full load). If using a stock ECU, a tuner can modify the ignition map via chip or piggyback. Always run colder spark plugs (NGK 7 or 8 heat range) and gap them tighter for boosted applications.

Step 5: Final Checks and First Start

Before cranking the engine, perform a thorough inspection.

  • Check all fluid levels — oil, coolant, power steering, brake fluid (if affected).
  • Inspect for leaks — fuel, oil, coolant connections. Tighten clamps and fittings.
  • Ensure all bolts are torqued to spec: head studs, intake manifold, exhaust manifold, turbo bolts, engine mounts.
  • Prime the oil system: remove the coil harness, unplug the fuel pump relay, crank the engine for 15 seconds (with starter) until the oil pressure gauge shows pressure. Re‑install the fuel pump relay and coil harness.

Running in the Engine

Start the engine. Let it idle for 15‑20 minutes, varying rpm between 1500 and 2500 during the first few minutes. Check for strange noises — valvetrain tick should be minimal. Look for exhaust leaks and overheating. After the first heat cycle, shut it down, let it cool, and re‑torque the head studs. Change the oil (break‑in oil) after 500 miles, then again at 1500 miles. Keep boost below 7 psi for the first 500 miles.

Performance Expectations and Next Steps

With these modifications — Ferrea valves, MLS head gasket, ARP studs, 440 cc injectors, Walbro fuel pump, and 10‑12 psi of boost — your RB20DET will comfortably make 250 hp at the wheels (around 280‑300 at the crank). The Ferrea valves will handle the higher rpm (7500+) without float, and the head gasket will prevent lift at elevated cylinder pressures.

If you want to go further (300+ hp), you’ll need larger injectors, a bigger turbo, and possibly forged pistons. But for a reliable street car that lights up the tires without breaking the bank, this setup delivers.

For further reading on RB20DET builds, check out Nissan Performance Magazine’s RB20 buildup series and the comprehensive RB20DET engine guide on Skyline Owners Club. For Ferrea valve specifications, refer to Ferrea’s official website.

The journey from a stock RB20DET to a 250‑hp powerhouse is well within reach of a dedicated home mechanic. Take your time, adhere to torque specs, and invest in a proper tune. The result is a engine that punches well above its displacement.