Mercury 312ci Specs: 3.80 x 3.44 in

Mercury 312ci specs: 3.80 x 3.44 in (96.5 x 87.4 mm) bore and stroke. Displacement, compression and factory ratings for each, plus rod ratio and piston speed.

At a glance

Displacement	312 ci
Cylinders	8
Bore	3.800"
Stroke	3.440"
Advertised power	210–260 hp
Years	1956–1960

This engine

Engine	Displacement	Bore × Stroke	CR	HP
Mercury 312ci (1956–1960)	312 ci	3.8" × 3.44"	—	210–260

Factory cars with a Mercury 312ci

• Mercury Montclair: 1956, 260 hp; 1957, 255 hp
• Mercury Monterey: 1956, 210 hp; 1956, 260 hp; 1957, 255 hp; 1958; 1959, 210 hp; 1960

What varies across the family

This family is represented by a single engine in the database: 312 ci, 8 cylinders, a 3.8" × 3.44" bore and stroke.

All 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 Mercury engines