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GMC Straight-6 engine
From Wikipedia, the free encyclopedia
GMC as a marque really only "owned" two engine designs, this straight-6 and a V8. The division "borrowed" many engines from other GM divisions, as noted below.
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In 1935 and 1936, GMC used Chevrolet's 207.
From 1937 through 1950, GMC used Oldsmobile's 230.
This information is incorrect.
GMC used the Oldsmobile flathead six in 1937 ONLY.
In 1938, GMC used Pontiac's 223.
GMC used the 235 in³ (3.9 L) Chevrolet Straight-6 engine as their base truck powerplant in the 1950s.
The Chevrolet 235 was bored out to 3.75 in (95.2 mm) to displace 261 in³ (4.3 L). This engine was offered as a step up from the 235 starting in 1954. It was replaced by the GMC V6 engine in 1960.
From 1963 through 1978, GMC had its own distinctive version of Chevrolet's straight-6, the 292.
GMC replaced the Pontiac 223 with their own 228 in³ (3.7 L) 228 in 1939. This side-valve engine was produced through 1953.
This is incorrect. This engine is a full pressure (60 psi) insert bearing motor with OVERHEAD valves - not "sid-valve" as stated above.
GMC also developed an OHV/pushrod engine in 1939. The 236 in³ (3.9 L) 236 was the first, lasting through 1955.
Those same years (1939-1955), GMC produced a 248 in³ (4.1 L) engine, the 248, which was similar to the 236.
The 256 in³ (4.2 L) 256 was different from the 236 and 248. It was also an OHV/pushrod engine, and was built for just two years, 1940 and 1941.
The last GMC-only straight-6 was the 270 in³ (4.4 L) 270. It was produced from 1941 through 1962 and was an OHV/pushrod engine.
The "other" last GMC-only straight-6 was the 302 in³ (4.4 L) 270. It was produced from the early 50s through 1959 was an OHV/pushrod engine. It was originally designed for the GMC military 2 1/2 ton trucks (M135 and M211).
This information is incomplete and misleading. The 302 engine was not a "270". The 302 GMC inline six was produced from 1952 to 1960 and is a 4" bore and 4" stroke engine. It was used in military 2.5 ton trucks with the HydraMatic transmission, however that engine was a sealed engine for snorkle/submersion use, had an electric fuel pump, and other features such as a deep sump oil pan. From 1952-1959, GMC manufactured the civilian 302 engine which was not sealed, had a mechanical fuel pump, and used a "standard" oil pan. This engine is popular with hotrod enthusiasts because it delivers tremendous power for an inline six engine, is truck built with a heavy cast block, and can take quite a bit of abuse.