Eliminate chronic balance shaft vibration and severe oil consumption with this Nissan Altima QR25DE Remanufactured Engine. Each 2.5L 4-Cylinder 16-Valve DOHC power plant features casting 6N2 block metallurgy and reinforced 4-bolt balance shaft mounting. Technicians must conduct complete cooling system vacuum bleeding and execute an exact 500-mile break-in oil change to protect the balance shaft and cam journal surfaces.

Manufactured with passenger-side block casting markings 6N2 and QR25DE, the aluminum open-deck engine block features centrifugal cast iron cylinder sleeves align-honed for crankshaft saddle roundness. The rotating group combines a micro-polished forged steel crankshaft casting AE0, balanced connecting rods, and hypereutectic pistons. Cylinder head casting 8H3 houses camshafts stamped I2 on intake and E4 on exhaust. Long block weight equals 240 lbs in crated dimensions of 36in length by 36in width by 36in height. Sump capacity measures 4.6 quarts.

Key Features of Nissan QR25DE

Professional engine builders buy Nissan QR25DE remanufactured engine assemblies to restore original vehicle torque and eliminate catastrophic catalytic converter dust ingestion damage. This long block replacement provides factory-matched reliability for transverse front-wheel-drive sedans.

- Reinforced 4-bolt balance shaft assemblies receive upgraded bearings to cancel secondary 4-Cylinder engine vibration.
- Cylinder head casting 8H3 undergoes CNC multi-angle valve seat cutting to maintain 0.001in runout.
- Camshafts stamped I2 and E4 provide factory lift and duration across all RPM ranges.
- Crankshaft casting AE0 journals receive micro-polishing to hold runout under 0.0003in TIR.
- Diamond plateau honed cylinder walls establish an Ra 16 micro-inch finish for piston ring seating.
- Multi-layer steel head gaskets prevent combustion gas blow-by across resurfaced aluminum decks.
- Intake variable timing control sprockets undergo ultrasonic cleaning and bench testing for phase response.

Dyno Load Precision Machining Tolerances

Dyno cell testing validates internal lubrication dynamics and shaft torque production before packaging. The 2.5L 2488cc DOHC engine produces 175 HP at 6,000 RPM and 180 ft-lbs of shaft torque at 4,000 RPM. Crankshaft main bearing oil clearances hold between 0.0011in and 0.0015in, while connecting rod clearance measures 0.0012in. Individual cylinder compression gauges show 185 PSI across all 4 cylinders. Hot engine oil pressure maintains 55 PSI at 3,000 RPM with regulated coolant operating temperatures stabilizing at 190°F.

Vehicle Fitment Drivetrain Guide

This engine fits 2002 to 2006 Nissan Altima and 2002 to 2006 Nissan Sentra models equipped with the 2.5L 2488cc QR25DE engine, casting 8H3 cylinder heads, and 4-bolt balance shaft assemblies. Drivetrains require front-wheel-drive configurations with manual or automatic transaxles. This unit does not fit post-2007 Altima platforms with casting JA0 heads, Nissan Frontier trucks, or Rogue crossovers due to distinct bellhousing bolt circles, crankshaft reluctor wheels, and oil filter locations.

Installation Protocol Service Requirements

Technicians must inspect the exhaust pre-catalytic converter for substrate breakdown, replace the exhaust manifold, and purge air from cooling passages during installation. Operational warnings restrict use in non-intercooled forced induction systems exceeding 6 PSI boost or demolition derby chassis lacking secondary engine oil cooling.

- Pre-fill the oil filter and prime the lubrication system with 5W-30 synthetic motor oil.
- Drain initial break-in oil and install a replacement oil filter after completing the first 500 miles.
- Check balance shaft gear lash and verify intake VTC solenoid electrical operation at 1,500 miles.

Warranty Terms Core Return Policy

This remanufactured long block includes our standard 3-Year Unlimited-Mile warranty for reliable road service. We provide free prepaid return freight shipping for your original core within 30 days of shipment receipt. The crated package contains the remanufactured long block, complete timing drive, oil pan, and valve cover assembly.