GMC 4-71 Specs

GMC 4-71 engine specs: 284 ci (4.65L), 4-cylinder, 4.252" bore x 4.4882" stroke, 18.7:1 compression.

Dimensions

Displacement284 ci / 4.65 L
Bore4.252"
Stroke4.4882"
Cylinders4
Compression ratio18.7:1
Bore/stroke ratio0.947

Construction

Block materialcast iron
Head materialcast iron
ValvetrainOHV
Fuel typediesel
Advertised HP140 hp

What these numbers mean

Bore/stroke character0.947 — undersquare — stroke exceeds bore, which favours low-end torque
Mean piston speed at 6,000 RPM4,488 ft/min — in the range typical of performance street engines
Displacement per cylinder71.0 ci
Static compression18.7:1 — high enough that pump premium or better is normally required

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