SD25, a variation of Nissan SD engines, is a 2.5L (2.488 cc) inline-4 diesel motor with water cooling.
Having compression index of 20.7 and 21.4 for Datsun and Nissan (non-California) and 21.9 for these vehicles within California standards, motor’s output is 70 hp (71 PS, 52 kW) at 4,000 rpm.
SD25 is the largest motor from the 4-cylinder SD range with 5 main bearing crankshaft and modernized rear main seal, constructed primarily for Nissan 720 (1983-1986) and Nissan D21 (1986-1988) vehicles. But, Nissan Urvan and Cabstar utilized it as well.
Depending on automobile mode and where it was sold, SD25 featured Kiki-Bosch in-line fuel or VE fuel injection pump.
All-in-one cylinder block with strong cast-iron construction keeps commutable dry liners. Moreover, the motor features 5 main bearings of precision type with a steel tri-metal body, iron-shod steel crankshaft featuring balance weights plus induction-hardened rods.
The engine gained an aluminum alloy piston, which is strong, lightweight, and has great heat conductivity; 1 oil control and 2 compression rings with chrome plating for better endurance. The cylinder bore is 89 mm (3.50 inches) while the piston stroke is 100 mm (3.94 inches).
With a solid and strong cast-iron cylinder head and shrink-mounted cast-iron valve sleeves, SD25 is provided with a qualitative cast-iron camshaft with lobes, developed to enhance endurance and rigidity.
SD 25 features OverHead Valve construction with 1 intake and 1 exhaust heat-resistant steel valve for each cylinder. Intake valves have a diameter of 40 mm and exhaust ones (featuring a stellite-processed exterior) are 34 mm.
The breakdown of the engine code is as follows:
- SD – Engine Family
- 25 – 2.5 Liter Displacement
Nissan SD25 Specs
| Engine code | SD25 |
| Layout | Straight-4, vertical |
| Fuel type | Diesel |
| Production | – |
| Displacement | 2.5 L, 2,488 cc (151.82 cu in) |
| Injection pump | Diesel Kiki-Bosch (in-line or VE) |
| Power adder | None |
| Max. Horsepower | 70 HP (71 PS, 52 kW) at 4,000 rpm |
| Torque output | – |
| Firing order | 1-3-4-2 |
| Dimensions (L x H x W): | – |
| Weight |
| Cylinder block | ||
| Cylinder block alloy | Cast iron | |
| Compression ratio: | 20.7:1 21.4 (only for Datsun/Nissan 720 Pickup, Non-California) 21.9 (only for Datsun/Nissan 720 Pickup, California) |
|
| Cylinder bore: | 89 mm (3.50 in) | |
| Piston stroke: | 100 mm (3.94 in) | |
| Number of piston rings (compression/oil): | 2 / 1 | |
| Number of main bearings: | 5 | |
| Block Height: | 268.00 mm (10.55 in) | |
| Cylinder liner inner diameter: | 89.000-89.035 mm (3.5039-3.5053 in) | |
| Piston skirt diameter | 88.895-88.935 mm (3.4998-3.5014 in) | |
| Piston ring side clearance: | №1 | 0.06 – 0.010 mm (0.0024 – 0.0039 in) |
| №2 | 0.04 – 0.08 mm (0.0016 – 0.0031 in) | |
| №3 | 0.02 – 0.06 mm (0.0008 – 0.0024 in) | |
| Piston ring end gap: | №1 | 0.30 – 0.45 mm (0.0118 – 0.0177 in) |
| №2 | 0.20 – 0.35 mm (0.0079 – 0.0138 in) | |
| №3 | 0.15 – 0.30 mm (0.0059 – 0.0118 in) | |
| Piston pin outer diameter | 25.993-26.000 mm (1.0233-1.0236 in) | |
| Piston pin bore diameter | 26.025-26.038 mm (5.5295 – 5.5335 in) | |
| Connecting rod center distance: | 170.0 mm (6.69 in) | |
| Crankshaft journal diameter: | 70.907-70.920 mm (2.7916-2.7921 in) | |
| Crankpin diameter: | 52.913-52.926 mm (2.0832-2.0837 in) | |
| Crankshaft center distance: | 50.00 mm (1.9685 in) | |
| Cylinder head | |
| Cylinder head alloy | Cast iron |
| Valve Arrangement: | OHV |
| Valves: | 8 (2 valves per cylinder) |
| Intake valves diameter: | 40.0 mm (1.575 in) |
| Exhaust valves diameter: | 34.0 mm (1.339 in) |
| Valves length: | 117.0 mm (4.61 in) |
| Intake valve stem diameter: | 7.970-7.985 mm (0.3138-0.3144 in) |
| Exhaust valves stem diameter: | 7.945-7.960 mm (0.3128-0.3134 in) |
| Camshaft journal diameter: | Front:45.434-45.447 mm (1.7887-1.7892 in) Center:43.897-43.910 mm (1.7282-1.7287 in) Front:41.218-41.231 mm (1.6228-1.6233 in) |
| Cam height: | 37.28-37.32 mm (1.4677-1.4693 in) |
What Cars Have A Nissan SD25 Engine?
| Model | Years Produced |
| Nissan 720 | 1983-1986 |
| Nissan D21 Pickup | 1986-1988 |
Nissan SD25 Engine Problems And reliability
SD motors are known for their reliability and great durability. Moreover, they don’t demand many services. Thanks to its industry-standard BOSCH injection system parts, constructed under license by Diesel Kiki, SD25 has almost no problems and can serve for many years.
Was this helpful?
The information provided in this article is for general informational purposes only. The author and publisher make no representations or warranties of any kind, express or implied, regarding the accuracy, adequacy, validity, reliability, availability, or completeness of any information presented. The reader is advised to consult a qualified professional, such as a mechanic or dealership, before making any decisions related to their vehicle's engine oil or maintenance.
