GMC LM1 specs: 350 ci (5.7L) 8-cylinder, 4.00 x 3.48 in (101.6 x 88.4 mm) bore and stroke. Built 1974–1979. Used in the Chevrolet Camaro. OHV.
The GMC Small Block Chevy (LM1) is oversquare — the 4" bore exceeds the 3.4799" stroke by 14.9% — a layout that favors airflow and RPM over leverage at the crank. The 3.4799" stroke puts mean piston speed at 4,000 ft/min around 6,900 RPM, which is where a production bottom end is generally considered at its limit. Each of the 8 cylinders displaces 43.8 ci (717 cc).
It is one of 27 engines in the Small Block Chevy family, sitting between the 265 ci and 400 ci members. 6 factory variants share these dimensions across 1974–1979.
Dimensions
Displacement
350 ci / 5.7 L
Bore
4"
Stroke
3.4799"
Cylinders
8
Configuration
V8
Compression ratio
8.2–8.5:1 (published figures vary)
Bore/stroke ratio
1.149
Construction
Block material
cast iron
Head material
cast iron
Valvetrain
OHV
Fuel type
gas
Firing order
1-8-4-3-6-5-7-2
Years
1974–1979
What these numbers mean
Bore/stroke character
1.149 — oversquare — bore exceeds stroke, which favours higher RPM and larger valves
Mean piston speed at 6,000 RPM
3,480 ft/min — conservative for a street engine
Displacement per cylinder
43.8 ci
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