GMC L35/LU3 specs: 262 ci (4.3L) 6-cylinder, 4.00 x 3.48 in (101.6 x 88.4 mm) bore and stroke. Rated 190 hp, 2002. Used in the GMC Safari and Chevrolet Astro.
The GMC L35/LU3 is oversquare — the 4" bore exceeds the 3.4803" stroke by 14.9% — a layout that favors airflow and RPM over leverage at the crank. The 3.4803" 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. A rod ratio of 1.638 is in the range most production engines fall in. Each of the 6 cylinders displaces 43.7 ci (716 cc).
It is one of 7 engines in the Vortec 4300 (4.3L V6) family, all of them 262 ci — the differences between them are in compression, heads and rating, not displacement.
Dimensions
Displacement
262 ci / 4.3 L
Bore
4"
Stroke
3.4803"
Cylinders
6
Configuration
V6
Rod length
5.7"
Rod ratio
1.638
Bore/stroke ratio
1.149
Construction
Block material
cast iron
Head material
cast iron
Valvetrain
OHV
Fuel type
gas
Firing order
1-6-5-4-3-2
Advertised HP
190 hp
Years
2002
Factory ratings by year
Year
Version
HP @ rpm
Torque @ rpm
Comp.
2002
L35/LU3 net
190 @ 4400 *
250 lb-ft @ 2800 *
—
Factory specification sheet. * Not yet cross-verified.
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
Rod ratio
1.638 — moderate — the range most production V8s fall in
Displacement per cylinder
43.7 ci
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