Buick LM1 specs: 350 ci (5.7L) 8-cylinder, 4.00 x 3.48 in (101.6 x 88.4 mm) bore and stroke, 8.2:1 compression. Rated 160 hp, 1978.
The Buick 350ci (LM1) is oversquare — the 4" bore exceeds the 3.48" stroke by 14.9% — a layout that favors airflow and RPM over leverage at the crank. The 3.48" 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).
8.2:1 is low by modern standards and generally happy on regular pump fuel.
It is one of 11 engines in the Buick 350ci family, all of them 350 ci — the differences between them are in compression, heads and rating, not displacement.
Dimensions
Displacement
350 ci / 5.7 L
Bore
4"
Stroke
3.48"
Cylinders
8
Configuration
V8
Compression ratio
8.2:1
Bore/stroke ratio
1.149
Construction
Fuel type
gas
Advertised HP
160 hp
Years
1978
Factory ratings by year
Year
Version
HP @ rpm
Torque @ rpm
Comp.
1978
LM1 net
170 @ 3800
270 lb-ft @ 2400
8.2:1
Factory specification sheet.
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
Static compression
8.2:1 — low by modern standards, generally happy on regular pump fuel
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