Nissan L20B: Everything You Need To Know

From 1967 through 1986, Nissan L series vehicle engines were built in both inline-four and inline-six designs with displacements ranging from 1.3 L to 2.8 L. This was the engine that powered the trusty Datsun 510, the renowned Datsun 240Z sports vehicle, and the first-generation upmarket Nissan Maxima. 

These engines are well-known for their exceptional dependability, longevity, and interchangeability of components. It has two valves per cylinder and a non-crossflow SOHC engine with an iron block and an aluminum head. 

The four-cylinder L series engines were replaced by the Z series, and then by the CA series, while the six-cylinder L series engines were replaced by the VG and RB series.

What are Nissan L20B Engines? 

From 1974 through 1985, the L20B was a massive 2.0 L engine. It generates 110 horsepower in 1974-75 with 112 lb-ft of torque as fitted in the Datsun 610 and 97 hp in 1977-78 with 102 lb-ft as installed in the 200SX. 

The Nissan L20B engine had larger-diameter main bearings while still using a fully counterweighted crankshaft. The usage of a six-bolt flywheel boss was also pioneered by the forged U60 crankshaft. To accommodate the larger stroke and connecting rods, the block featured a higher deck height. Later in the Z20 and Z22 engine series, this standard would be employed as well.

The larger engine even spawned an important new option from Datsun’s competition department: -50mm Solex twin-choke carburetor kits-complete fuel systems that help provide nearly twice the power of the standard L20B. 

This engine’s famous toughness and almost square design have made it a popular option for turbocharging among tuners.

Engine Specifications and Design:

  • Production Run: 1974 – 1985
  • Cylinder Head Material: Aluminum
  • Cylinder Block Material: Aluminum
  • Configuration: Inline 4
  • Bore: 85.0 mm
  • Stroke: 78.0 mm
  • Valvetrain: SOHC two valves per cylinder
  • Displacement: 2.0 L (2460 cc)
  • Compression Ratio: 8.5
  • Weight: 250 lbs.
  • Maximum HP: 110 HP at 3,500 – 4,000 RPM
  • Maximum Torque: 112 lb-ft at 1,900 – 2,500 RPM

Cylinder Block

The cylinder block of the Nissan-Datsun L20B engine is made of cast iron. A five-bearing-support system is used in the cylinder block, a mono-block unique casting construction. 

Cooling jackets surround the cylinder bores, which are machined directly in the block. The oil ways in the block are configured so that the full-flow oil filter is immediately coupled to the block’s right side. The cylinder bore of the Nissan L20B engine is 85.0 mm and the piston stroke is 86.0 mm, with a compression ratio of 8.5.

The crankshaft is a unique steel forging that produces smooth, steady power at high speeds. There are eight balancing weights in the engine. The pistons are made of an unique aluminum alloy and feature two compression rings and one combined oil ring to limit thermal expansion. 

In addition to that, the piston heads have a modest dished shape. The piston pin is a hollow steel shaft with a specific shape. It is press-fit to the connecting rods and fully floating to the piston. The connecting rods are made of forged special steel.

Cylinder Head

The cylinder head is built of a lightweight and sturdy aluminum alloy with high cooling efficiency, and it has wedge-type combustion chambers. The intake valve has a specific aluminum bronze valve seat, while the exhaust valve has a heat resistant steel valve seat. All of these components are hot press-fitted. 

The camshaft is housed under the rocker cover and is composed of unique cast iron. The camshaft is supported by four aluminum alloy brackets. Camshaft bearings are lubricated via oil holes that feed to the cylinder head’s primary oil gallery. Concentric channels are drilled in the camshaft’s front and back halves.

The cam mechanism directly activates a pivot type rocker arm in the valve system. The dual-type valve springs are used in the Nissan L20B engine. The intake valves are 42 mm (1.65 in) in diameter, while the exhaust valves are 35 mm (1.65 in) (1.37 in).  The intake valve duration is 248 degrees, and the valve lift is 10.0 millimeters (0.39 inch); the exhaust valve duration is 248 degrees, and the valve lift is 10.5 millimeters (0.39 inch) (0.41 in). 

A double row roller chain powered by the crankshaft drives the camshaft. A chain tensioner, which is actuated by a spring and oil pressure, controls the tension of the chain. 

The intake manifold is cast aluminum alloy, while the exhaust manifold is cast iron.

Applications of Nissan L20B Engine: 

  • 1974 – 1976 Datsun 610
  • 1975 – 1977 Datsun 710
  • 1975 – 1979 Datsun 620 110 HP
  • 1975 – 1979 Datsun 200SX
  • 1977 – 1981 Datsun 200B
  • 1978 – 1981 Datsun 510
  • 1979 – 1980 Datsun 720
  • 1981 – 1984 Nissan Datsun Skyline R30 

Engine Potential: 

Getting an L-series (2 or 2.2 liter) to create 200 horsepower at the wheels will be a tremendous problem for you; I don’t think it’s doable naturally aspirated. It’ll be incredibly pricey, and the motor will be strung out like a tight rubber band waiting to snap. 

It also won’t be very street-able, since it will most likely overheat, have a horrible idle, and only run well at 6500 rpm. Fully ported heads, cam, valves, pistons, rods, 13:1 compression rating. After that, everything will have to be massaged to perfection, and have the engine to be driven on racing gas all of the time.

The L-series likes to make all of their torque down low and then peter out as the RPM rises, due in part to the poor flowing heads. If you are already set on going with the L and have a lot of cash lying around, then get a longblock built by Rebello or a similar race engine place, because that is what you are looking for, a full race motor. 

The L-series was a fine engine in its day, and it is still as tough as nails, but things have changed tremendously. If you want to turbo it, you will need to EFI it, use a standalone, and possibly create your own manifold, maybe rebuild it, and it will still be slower than a factory SR20DET in a 510.

The search for the perfect L turbo has been difficult, but that’s because there are a few out on the market. You know what they say: if you can’t beat ’em join em. 

Regardless of your decision-making process when it comes time to buying this part – which will be entirely dependent upon how much power and torque we want, make sure not only do I have all bases covered in terms or reliability as well as cost effectiveness; don’t forget about other factors such like longevity due from parts replacement too.

The twin carburetor system is not responsible for vapor lock as was previously thought – heat shields can be purchased but tuning them requires expertise which only few possess. This leads most owners feeling frustrated when trying get optimum performance from the car at times due in part due its antiquated design features like sync switching needles between carbs ;although there some who understand how.

You may opt not to go through the 510 learning curve stage, save some money and a lot of time by changing your engine right away. A VG, KA or SR appear popular alternatives but you could change anything you want into it! The engines indicated above will produce 200 HP at back wheels much simpler than an L series while driving just as well too.

Problems Surrounding Nissan L20B Engine: 

The Nissan L20B engines are not only durable engines but also rare; every passing day, it gets rarer and elusive. These engines despite their age, if properly maintained, is an excellent engine that is fairly dependable – 400-500k trouble-free miles. 

Some consumers reported wide range of issues, however this was mainly due to, yes you guessed it – age, mileage, and overall condition.

Among the other concerns are:

1. Crankcase Ventilation Issues

There are reports from some owners that the crankcase ventilation tube pops out after the engine begins to idle and eventually dies out after a few minutes. Some of its manifestations include intermittent engine breakdown and engine dying out. 

It can also be caused by a bad ignition. 

2. Valve Cover Gasket Leaks

The oil is spilling from the valve cover vent hose. Because you have a Weber, it should be linked to the air filter. The block vent pipe or the hose connecting it to the PCV valve is broken or missing, and oil is leaking onto the header.


Despite its outdated stylings, the Nissan L20B or Datsun 620 engine makes old-school enthusiasts want to buy one. There are many factors to this. First, Datsuns stay indefinitely for some reason, as if Datsun employees massaged it around the automobiles and manufactured some sort of anti-wrinkle cream.

Second, all Japanese automobiles manufactured in the 1970s appear fresh lowered and for the earth, coming up for the region appearing feeling a little extra flavor. Last but not least, Datsun engines are built like tanks, powerful and reliable, and lights up like a total spotlight. 

Throughout general, what the Datsun executives accomplished under the sun is quite outstanding. It’s interesting how few people tune these types of trips these days.

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