Volvo B18A Specifications
| Engine Model: Volvo B18A |
| Engine Type: 4-cycle inline 4-cylinder OHV 8-valve liquid-cooled gasoline |
| Total Displacement: 108.5 cu.in (1.78 L) |
| Rated Engine Power: 75-100 Hp (56-74 kW) at 5000 rpm |
| Fuel System Type: Carburetor or electronic fuel injection |
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The Volvo B18A engine is an inline-four
cylinder, overhead valve (OHV) gasoline powerplant. Introduced in 1961,
it served as the successor to the Volvo B16 engine and became the
foundational engine for Volvo's renowned reputation for durability and
reliability throughout the 1960s. This engine features a robust cast
iron cylinder block and cylinder head, a three-bearing crankshaft, and a
single, side-mounted camshaft driven by a timing chain.
The B18A was designed with a focus on longevity, torque, and
straightforward maintenance. It powered a wide range of Volvo's iconic
models, from the Amazon/120 series to the P1800 sports car. Known for
its distinctive exhaust note and steadfast operation, the B18A
established engineering principles that influenced Volvo's engine design
for decades. Its robust construction allowed for significant tuning
potential in high-performance applications.
Engine family: B18.
Engine type: Inline-four cylinder, four-stroke Otto cycle, overhead
valve (OHV).
Displacement: 1778 cc (108.5 cubic inches).
Bore: 84.14 mm (3.312 inches).
Stroke: 80.0 mm (3.150 inches).
Compression ratio: 8.5:1 for standard B18A versions; 10.0:1 for
high-compression B18B variants.
Maximum power output: 75 Hp (56 kW) at 4500 rpm for single carburetor
B18A.
Maximum power output: 90 Hp (67 kW) at 5000 rpm for twin-carburetor
B18B.
Maximum power output: 100 Hp (74 kW) at 5500 rpm for fuel-injected B18E.
Maximum torque output: 110 lb-ft (149 Nm) at 2500 rpm.
Firing order: 1-3-4-2.
Engine orientation: Longitudinal, inclined 15 degrees to the right.
Aspiration: Naturally aspirated.
Fuel type: Gasoline.
Recommended oil grade: SAE 20W-50 or SAE 30 monograde.
Oil capacity: 4.5 liters (4.8 U.S. quarts), including filter.
Coolant capacity: 8.5 liters (9.0 U.S. quarts).
The cylinder block is a single, heavy casting from grey cast iron. It is
an extremely robust design, providing high rigidity and excellent
acoustic damping. The block incorporates four cylinder bores, cast
integrally. The crankshaft is supported by three main bearings. This
three-bearing design is a characteristic of the engine, contributing to
its compact length but requiring a particularly stiff crankshaft.
The crankshaft is a forged steel component, extensively counterweighted.
Main bearing caps are cast iron and secured with two studs and nuts
each. Connecting rods are forged from steel, with a traditional I-beam
shape. Pistons are cast aluminum alloy, with a flat crown. Each piston
is fitted with three rings: two compression rings and one oil control
ring. The block features deep water jackets for effective cooling.
The cylinder head is a cast iron unit. It employs a side-mounted
camshaft (located in the block) and overhead valve (OHV) layout, with
valves operated via pushrods and rocker arms. The camshaft is driven by
a single roller chain from the crankshaft. Valve actuation sequence:
camshaft lobe lifts tappet, which pushes a hardened steel pushrod, which
acts on a rocker arm pivoting on a shaft, finally depressing the valve
spring and opening the valve.
The engine uses two valves per cylinder (one intake, one exhaust),
inclined in a hemispherical combustion chamber. Valve clearance is
adjusted via a screw and locknut on each rocker arm. Intake valves are
larger than exhaust valves. Valve seats are cut directly into the cast
iron head.
The fuel system varies by version. The base B18A uses a single Solex or
Zenith downdraft carburetor with a fixed venturi. The
performance-oriented B18B employs twin SU HS6 sidedraft carburetors,
which are constant-vacuum (piston) type carburetors requiring periodic
synchronization. The advanced B18E version, used in the P1800E, features
Bosch D-Jetronic electronic fuel injection.
This early analog system uses a manifold air pressure sensor,
temperature sensors, and electromagnetic injectors mounted in the intake
manifold. All versions use a mechanical fuel pump, driven by an
eccentric on the camshaft, to lift fuel from the tank to the carburetor
or injection system. A manual choke is used on carbureted versions.
The lubrication system is a pressure-fed, full-flow filtration wet-sump
design. A gear-type oil pump is driven by a skew gear from the camshaft.
Oil is drawn from the stamped steel oil pan through a pickup screen. The
oil is pressurized and forced through a replaceable, canister-type
full-flow oil filter. From the filter, oil enters the main gallery.
It supplies the three main crankshaft bearings and the camshaft
bearings. Drilled passages in the crankshaft feed the connecting rod
bearings. Oil is pumped up through hollow pushrods to lubricate the
rocker arms and valve stems before draining back to the sump. Oil
pressure is monitored by a mechanical gauge. The system incorporates an
oil cooler as standard, mounted to the block.
The cooling system is a pressurized, pump-circulated thermosiphon
system. A centrifugal water pump is driven by a V-belt from the
crankshaft pulley. Coolant circulates through the block and head,
exiting to a copper-brass tube-and-fin radiator. A bellows-type
thermostat regulates coolant flow. The system is designed for robust
operation.
The ignition system is a conventional coil-and-distributor type. The
distributor is driven by a skew gear from the camshaft and features
centrifugal advance weights and a vacuum advance diaphragm. The
generator (or alternator in later models) is V-belt driven. A crankcase
ventilation system (PCV) routes blow-by gases from the rocker cover to
the intake manifold.
The external dimensions of the B18A engine are compact due to its
three-bearing crankshaft and OHV design. Approximate length is 650 mm
(25.59 inches). Approximate width is 600 mm (23.62 inches). Approximate
height is 700 mm (27.56 inches). These dimensions include the
carburetor, generator, and fan. The weight of a complete B18A engine,
with all fluids and standard accessories, is approximately 155 kg (342
lbs). The extensive use of cast iron contributes to this mass.
Engine oil and filter change intervals were 5000 km (3,107 miles) or
every six months under period service schedules. Valve clearance
adjustment via the rocker arm screws is a critical and frequent service
task, required every 10,000 km (6,214 miles). The points, condenser, and
spark plugs require regular adjustment, cleaning, and replacement.
The timing chain should be inspected for wear and stretch every 50,000
km (31,069 miles). Carburetors require balancing (on twin-carb versions)
and periodic overhaul. The coolant should be drained and replaced
annually. The fuel pump diaphragm should be inspected for integrity. The
distributor advance mechanisms require periodic lubrication and
functional checking.
Torque values are specified for clean, dry threads. Cylinder head bolts
are tightened in a specific sequence to 7.5-8.0 kgm (54-58 lb-ft / 74-78
Nm). Main bearing cap nuts: 6.5-7.0 kgm (47-51 lb-ft / 64-69 Nm).
Connecting rod cap nuts: 5.0-5.5 kgm (36-40 lb-ft / 49-54 Nm).
Crankshaft pulley bolt: 12.0-13.0 kgm (87-94 lb-ft / 118-127 Nm).
Camshaft sprocket bolt: 5.5-6.0 kgm (40-43 lb-ft / 54-59 Nm). Spark
plugs: 3.0-3.5 kgm (22-25 lb-ft / 29-34 Nm). Oil drain plug: 4.0-4.5 kgm
(29-33 lb-ft / 39-44 Nm). Rocker shaft support bolts: 2.0 kgm (14 lb-ft
/ 20 Nm).
The Volvo B18A engine was the primary powerplant for Volvo's core models
from 1961 to 1968, after which it was evolved into the B20. Applications
are extensive: Amazon/120 Series (121, 122S, 123GT). P1800 and P1800S
sports car (including the famous P1800 driven by Roger Moore in "The
Saint"). Volvo 140 Series (early 1967 models). Volvo Duett (late
production). Volvo PV544 (late production).
The B18B high-compression twin-carb version was used in the 122S and
P1800S. The B18E fuel-injected version was exclusive to the 1969-1970
P1800E. The engine's legacy is immense, forming the reliable core of
Volvo's identity during its key growth period and establishing a
benchmark for four-cylinder durability.
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