Volkswagen B Specs: 85.5 x 69 mm (3.3661 x 2.7165 in), 57 hp

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Volkswagen B specs: 1.6L (96.6 ci) 4-cylinder, 85.5 x 69 mm (3.3661 x 2.7165 in) bore and stroke, 7.5:1 compression. Rated 57 hp, 1970. OHV.

The Volkswagen Air-cooled Flat Four (B) is oversquare — the 3.3661" bore exceeds the 2.7165" stroke by 23.9% — a layout that favors airflow and RPM over leverage at the crank. The 2.7165" stroke does not reach 4,000 ft/min of mean piston speed until about 8,850 RPM, so piston speed is not what limits this engine's revs — valvetrain and breathing are. Each of the 4 cylinders displaces 24.2 ci (396 cc).

7.5:1 on aluminum heads is low by modern standards and generally happy on regular pump fuel.

It is one of 28 engines in the Air-cooled Flat Four family, the largest at 96.6 ci.

Dimensions

Displacement96.6 ci / 1.6 L
Bore3.3661"
Stroke2.7165"
Cylinders4
Compression ratio7.5:1
Bore/stroke ratio1.239

Construction

Block materialmagnesium alloy
Head materialaluminum
ValvetrainOHV
Fuel typegas
Advertised HP57 hp
Years1970

What these numbers mean

Bore/stroke character1.239 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves
Mean piston speed at 6,000 RPM2,717 ft/min — conservative for a street engine
Displacement per cylinder24.1 ci
Static compression7.5:1 — low by modern standards, generally happy on regular pump fuel

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