The Nissan 370Z, powered by the VQ37VHR engine, has earned a formidable reputation among sports car enthusiasts for its robust construction and remarkable tuning potential. While the stock 332 horsepower provides an engaging driving experience, the aftermarket community has demonstrated that this engine can reliably deliver substantially more power. Achieving the 650+ horsepower mark, however, requires a meticulous approach: custom-built internal components, a carefully selected forced induction system, and comprehensive supporting modifications. This article provides a detailed, production-oriented guide to building a 370Z capable of exceeding 650 wheel horsepower using custom internals and SST turbochargers—a goal that transforms the car into a genuine supercar contender.

Before diving into the parts list, it is essential to understand that 650+ horsepower at the wheels is not merely a matter of bolting on larger turbochargers. The VQ37VHR’s factory internals are strong enough for moderate boost (typically up to 450-500 whp), but beyond that threshold, the block, pistons, rods, and valvetrain must be upgraded to withstand the immense thermal and mechanical stress. This guide assumes a comprehensive build aimed at maximum reliability, not just peak numbers.

Understanding the VQ37VHR Engine Architecture

The VQ37VHR is a 3.7-liter, 60-degree V6 introduced in 2007. It is a direct evolution of the earlier VQ35HR, sharing the same bore center spacing and overall architecture but with increased displacement via a longer stroke (96.0 mm bore, 85.0 mm stroke). Key distinguishing features include Nissan’s VVEL (Variable Valve Event and Lift) system, which allows continuously variable intake valve lift and timing, contributing to both low-end torque and high-RPM power. The engine also utilizes a timing chain, a robust cast-iron main bearing ladder, and an aluminum-alloy block with pressed-in iron cylinder liners.

For a 650+ horsepower build, several inherent design characteristics are advantageous: the closed-deck block design (initially found on later VQ37VHR variants) provides excellent cylinder rigidity under boost, and the dual knock sensors allow aggressive ignition timing when running high-octane fuel. However, the stock pistons are hypereutectic cast aluminum with relatively thin ring lands, and the connecting rods are powdered-metal forgings—adequate for factory outputs but not for sustained high boost. The crankshaft is forged steel and is generally considered durable enough for 650 hp, but many builders still opt for a fully counterweighted aftermarket crank for extra safety margin.

The 650 HP Goal: What It Means in Practice

A true 650 wheel horsepower (whp) from a VQ37VHR equates to roughly 740-800 horsepower at the crank, depending on driveline losses. This power level places the 370Z in the same performance bracket as high-end European supercars from a decade ago. Achieving this requires a careful balance of turbocharger sizing, compression ratio, fuel system capacity, and thermal management. Typical boost levels for such a build range from 18 to 22 psi on pump gas, or 22-28 psi on ethanol blends (E85).

It is crucial to note that 650 whp is a threshold where many factory components—including the clutch, transmission, differential, and axles—become the weak points. This guide focuses primarily on the engine, but a complete build must include drivetrain upgrades to avoid catastrophic failure on the first hard pull. We will touch on key drivetrain considerations in the supporting modifications section.

Custom Built Internals: The Foundation for 650+ HP

Upgrading the VQ37VHR’s internals is non-negotiable for a reliable 650+ horsepower build. The following components must be replaced with high-strength, forged alternatives. Every part should be chosen based on proven real-world results from reputable builders.

Pistons and Rings

The stock hypereutectic pistons will crack ring lands under sustained high boost. For a 650 whp goal, you need forged pistons from a manufacturer like CP-Carrillo, JE, or Wiseco. Typical specifications:

  • Compression Ratio: Lowered to 9.0:1 – 9.5:1 (from the stock 11.0:1) to allow safe boost levels on pump gas. For E85 dedicated builds, 10.0:1 can be used.
  • Material: 2618 aluminum alloy for maximum strength under thermal cycling.
  • Ring Pack: 1.2 mm, 1.2 mm, 2.8 mm with a high-tension top ring for good oil control at high boost.
  • Coating: Skirt coating (e.g., Grafal or similar) to reduce scuffing during cold starts.

Many builders also pin the oil squirters—or remove them entirely when using forged pistons—to prevent excessive oil cooling that can lower oil pressure. Consult your engine builder for the exact approach.

Connecting Rods

The factory powdered-metal rods are adequate to about 500 whp but will bend under the compressive loads of 650+ whp. Forged billet or forged 4340 steel rods from Manley, Carrillo, or K1 Technologies are standard. Key considerations:

  • Length: Stock length (146.5 mm center-to-center) or a longer aftermarket rod (149.05 mm) combined with a custom piston pin height to alter the rod/stroke ratio for better high-RPM stability.
  • Fasteners: ARP 2000 or L19 bolts rated for high clamping load. Torque to yield must be followed precisely.
  • Weight: Choose a design that is appropriately lightened but not excessively so; a rod that is too light may sacrifice strength.

Crankshaft and Main Bearings

The OEM forged crankshaft is a high-quality piece and has been used successfully in builds exceeding 800 whp. However, at 650 whp, it is wise to have the crank micro-polished, shot-peened, and knife-edged to reduce rotating mass. Many builders also replace the factory main bearing with a high-performance tri-metal bearing from ACL or King Bearings to handle higher oiling demands. If budget allows, a fully counterweighted aftermarket crank from one of the major billet manufacturers eliminates any lingering doubts about the nitrided OEM unit.

Cylinder Head Modifications

The VQ37VHR cylinder heads are capable of flowing enough air for 650 whp with minimal porting, but the valvetrain must be upgraded to handle higher lift, longer duration, and higher spring pressures. Significant improvements come from:

  • Valve Job and Porting: A multi-angle valve job and mild bowl blending to reduce turbulence. Full CNC porting is rarely necessary below 700 whp unless running large turbochargers.
  • Valves: Inconel exhaust valves (often 1-piece, sodium-filled from the factory can be replaced for durability). Oversized intake valves (38 mm vs stock 36 mm) can add flow but require corresponding seat machining.
  • Valve Springs and Retainers: Dual springs with titanium retainers from Supertech, Brian Crower, or GSC Power-Division. Spring seat pressure of 90-100 lbs and installed height set correctly to prevent valve float at 7500+ RPM.
  • VVEL System: The VVEL actuator and eccentric shafts are generally durable up to 7500 RPM. For higher redlines (7800-8000 RPM), some builders upgrade the actuator or replace it with a solid shim system to eliminate potential failure. Note: deleting VVEL is an option but requires a standalone ECU and intake cam gear.

ARP cylinder head studs (1/2 inch) are mandatory. The factory head bolts stretch under high cylinder pressure; studs maintain consistent clamping force.

SST Turbochargers: Selection and Setup

The term “SST turbochargers” in the context of the VQ37VHR typically refers to a specific twin-turbo kit developed by a company like Z1 Motorsports (Z1 uses Garrett and BorgWarner offerings) or another specialist fabricator. SST branding may stand for “Super Street Turbocharger” or a proprietary line. Regardless, the principles of turbocharger selection remain the same. For a 650 whp goal, twin turbochargers are the most common configuration because they allow for compact packaging, quicker spool, and even distribution of exhaust pulses to the V6.

Turbocharger Sizing

Correct sizing is critical: too small and the turbos become restrictors at high RPM, too large and the car will have excessive lag. For 650 whp on a 3.7L V6, two equal-sized GTX3071R Gen II or equivalent (BorgWarner EFR 7163 or Precision 5858) turbos are popular. These provide:

  • ~65 lb/min total airflow capacity (32-33 lb/min per turbo), ample for 650 whp.
  • Quick spool: full boost by 3800-4000 RPM with proper exhaust manifold design.
  • Efficiency up to 25-26 psi boost.

Alternatively, a single large turbo (like a Garrett GTX3584R) can also work but requires a complex log or tubular header manifold and may introduce packaging issues with the 370Z’s tight engine bay. Twin turbos remain the proven path for this chassis.

Wastegates and Blow-Off Valves

Boost control is handled by high-quality external wastegates (Tial MVR 38 mm or Turbosmart 40 mm) mounted to the exhaust manifolds. For 650 whp, two 38 mm wastegates (one per turbo) are sufficient. Use a high-capacity blow-off valve such as a Tial Q or Turbosmart Kompact EM on the cold side of each turbo or a single large unit in the intercooler piping.

Intercooler and Piping

An air-to-air intercooler capable of supporting 700+ whp is required. The core should be bar-and-plate design, approximately 24 x 12 x 4 inches. Piping diameter should be 2.5 to 3 inches to reduce pressure drop. Mandrel-bent aluminum tubing with silicone couplers and T-bolt clamps is standard.

Installation Considerations

Professional installation is strongly recommended. The 370Z’s engine bay is accessible but cramped. The stock alternator often requires relocation or a smaller high-output unit. A custom oil catch can system must be plumbed to the valve covers to prevent oil mist from entering the intake tract under high boost. Many tuners also advise adding a vacuum pump to reduce crankcase pressure and improve ring seal.

Supporting Modifications for Reliability and Performance

Even with a perfectly built short block and turbo system, the rest of the vehicle must be addressed. Neglecting supporting modifications is the most common reason for failure at this power level.

Fuel System

Stock injectors (323 cc/min) and fuel pump are inadequate past ~400 whp. For 650 whp, you need:

  • Injectors: 1000-1300 cc/min (low impedance) for E85; 850-1000 cc/min for pump gas. Injector Dynamics (ID1050x) or Bosch EV14-style injectors with adapters for the VQ37VHR are common.
  • Fuel Pump: A brushless or high-flow in-tank pump (e.g., Walbro 525, AEM 380 lph) plus a surge tank or a second pump in a parallel setup. Many builds use a fuel cell with a Magnafuel pump mounted in the rear.
  • Fuel Lines: -6AN feed and -6AN return lines to handle the volume. Teflon-lined lines are recommended for ethanol compatibility.
  • Flex Fuel Sensor: If you plan to run E85, install a GM-style flex fuel sensor to allow the ECU to automatically adjust timing and fuel maps.

Always consult a professional tuner for injector sizing and fuel system pressure requirements. Dropping fuel pressure under load will cause lean conditions and engine damage.

Engine Management and Tuning

The stock ECU with an EcuTek or UpRev flash tune can handle 650 whp with proper calibration, but many enthusiasts switch to a standalone system like a Haltech Elite 2500, Motec M130, or AEM Infinity for full control and safety features. Tuning should be performed on a chassis dynamometer by a certified tuner with VQ37VHR experience. Key parameters to monitor:

  • Air-fuel ratio (AFR): 11.5-12.0 on pump gas, 7.5-8.5 on E85 (lambda 0.7-0.75).
  • Ignition advance: conservative timing (10-14 degrees under boost) to avoid detonation.
  • Boost control: closed-loop solenoid to manage boost curve and prevent overshoot.
  • Knock control: OEM knock sensors can be used; standalone ECUs can add dual knock input for safety.

Cooling System

Thermal management is critical. At 650 whp, engine oil temperatures can exceed 300°F on a track day. The following are strongly recommended:

  • Oil Cooler: A large-setup oil cooler with a thermostat (Setrab or Mishimoto, 19-25 row core) mounted in the front bumper area.
  • Radiator: A high-capacity aluminum radiator (Mishimoto, Koyo) with dual electric fans and a shroud.
  • Intercooler: As noted, ensure the intercooler is sized for the power level and has adequate airflow ducting.
  • Water Pump: Consider an electric water pump (e.g., Davies Craig) to run the pump at lower speed during idle and full speed under load, reducing parasitic loss and improving cooling.

Exhaust System

A free-flowing exhaust reduces backpressure and spool time. For twin-turbo applications, a 3-inch downpipe from each turbo merging into a single 3.5- to 4-inch exhaust with a high-flow catalytic converter (or off-road test pipe) is standard. Mufflers should be designed to flow well while keeping noise within track limits.

Drivetrain Upgrades

650 whp will destroy the stock clutch, transmission, and differential if left stock. Essential upgrades:

  • Clutch: A twin-disc clutch (e.g., ACT, Competition Clutch, OS Giken) rated for 800-900 ft-lbs. A heavy-duty pressure plate is necessary.
  • Flywheel: Lightweight chromoly or billet steel flywheel (18-20 lbs) to maintain rotational inertia for streetability.
  • Transmission: The stock CD009 six-speed manual can hold 650 whp with regular fluid changes and careful driving, but synchros may wear faster. Consider a built transmission with carbon synchros and upgraded shift forks. An automatic (7-speed) will require a full rebuild with stronger clutches and upgraded valve body.
  • Differential: An LSD upgrade (OS Giken Super Lock or Nismo GT Pro) with reinforced mounting bushings. The axles should be replaced with upgraded units from The Driveshaft Shop or similar to prevent snapping.

Reliability Considerations and Maintenance

Building a 650+ horsepower 370Z is not a “set it and forget it” project. The engine requires regular maintenance and monitoring. Key tips:

  • Oil: Use a high-quality 5W-40 or 10W-40 synthetic (e.g., Motul 300V, Castrol Edge) and change it every 3000 miles or after every track day.
  • Coolant: Use a proper coolant mixture (30-50% coolant, rest distilled water) with a corrosion inhibitor. Do not rely solely on waterless coolants.
  • Boost Leaks: Check all intercooler piping and silicone couplers regularly. A boost leak at 20 psi can cause a lean condition and disastrous detonation.
  • Data Logging: Run a data logger (e.g., AiM Solo, MoTeC dash) to monitor AFR, boost, oil pressure, and exhaust gas temperature on every pull. Set warnings for critical thresholds.
  • Warm-Up and Cool-Down: Let the engine idle for 1-2 minutes before driving, and after a hard session, let it cool for 2-3 minutes before shutdown (or install a turbo timer).

Some tuners recommend limiting the RPM to 7500 instead of the stock 7800 to reduce stress on the valvetrain, even with upgraded components.

Conclusion: A Carefully Engineered Path to 650+ HP

Achieving 650+ horsepower from the Nissan 370Z’s VQ37VHR engine is an ambitious but attainable goal when approached with proper planning and high-quality components. The three pillars of a successful build are custom forged internals (pistons, rods, and valvetrain), correctly sized SST turbochargers (twin GTX3071R or similar), and comprehensive supporting modifications that address fuel, cooling, tuning, and drivetrain weaknesses. Cutting corners on any of these areas will result in reliability issues or, worse, catastrophic failure.

For those embarking on this journey, it is wise to consult with established builders and tuners who have experience with VQ engines at high power levels. Forums such as The370Z.com and vendors like Z1 Motorsports offer extensive documented builds. A build of this magnitude is not inexpensive; expect to spend between $15,000 and $25,000 for a turnkey engine and power train setup, not including the cost of the car. However, the reward is a 370Z that can run with cars costing three times as much, delivering a visceral driving experience that few modern cars can match.