Porsche 78ci Engine Specs

Bore, stroke, displacement and compression for all 2 Porsche 78ci engines, compared side by side. Plus rod ratio and head specs where published.

At a glance

Displacement	78 ci
Cylinders	4
Bore	2.933–3.150"
Stroke	2.520–2.913"
Compression	6.5:1
Advertised power	44–60 hp
Years	1951–1957

Engines in this family

Engine	Displacement	Bore × Stroke	CR	HP
506	78 ci	3.1496" × 2.5197"	6.5:1	44
589	78 ci	2.9331" × 2.9134"	—	60

Factory cars with a Porsche 78ci

• Porsche 356: 1951, 44 hp; 1952, 44 hp; 1953, 44 hp; 1954, 44 hp; 1954, 60 hp; 1955, 44 hp; 1955, 60 hp; 1956, 44 hp; 1956, 60 hp; 1957, 44 hp; 1957, 60 hp

What varies across the family

Both bore and stroke vary across the family, so these are separate castings rather than variations on one block.

1 of 2 are oversquare — bore larger than stroke, which favours revs over low-end torque.

Each engine page carries rod ratio, mean piston speed, bore/stroke character and cylinder head specs where published, and links into the calculators with its dimensions already filled in.

← All Porsche engines