Plymouth M-code Specs: 4.319 x 3.752 in, 375 hp

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Plymouth M-code specs: 440 ci (7.2L) 8-cylinder, 4.319 x 3.752 in (109.7 x 95.3 mm) bore and stroke. Rated 375 hp, 1969. Used in the Plymouth Barracuda. OHV.

The Plymouth M-code is oversquare — the 4.3189" bore exceeds the 3.752" stroke by 15.1% — a layout that favors airflow and RPM over leverage at the crank. The 3.752" stroke puts mean piston speed at 4,000 ft/min around 6,400 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 55.0 ci (901 cc).

It is one of 25 engines in the RB family, the largest at 440 ci.

Dimensions

Displacement440 ci / 7.2 L
Bore4.3189"
Stroke3.752"
Cylinders8
ConfigurationV8
Bore/stroke ratio1.151

Construction

Block materialcast iron
Head materialcast iron
ValvetrainOHV
Fuel typegas
Advertised HP375 hp
Years1969

What these numbers mean

Bore/stroke character1.151 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves
Mean piston speed at 6,000 RPM3,752 ft/min — in the range typical of performance street engines
Displacement per cylinder55.0 ci

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