GMC V6 engine
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GMC produced a unique 60° V6 V6 engine from 1960 through 1978. The engine was available in 305, 351, 401 and 478 in³ (5.0, 5.8, 6.6, and 7.8 L) version. In late production there was also a 432 in³ (7.1 L) version with enlarged crankshaft journals. GM also made a 637 in³ (10.4 L) 60° V8 with twin balance shafts using the same general layout as the 305. Finally, there was a 702 in³ (11.5 L) "Twin Six" V12, which was basically two 351s placed end-to-end with a common block and crank. A Diesel version was called the ToroFlow.
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[edit] 305
The 305 in³ (5.0 L) 305 had a 4.25 in (107.9 mm) bore and 3.58 in stroke (90.9 mm). The 305 V6 was the standard pickup truck engine for GMC from 1960 to 1966, and was one of the first V6 engines produced by an American company.It was also in a 1969 GMC 2500 Super Camper Special.
[edit] 351
The 351 in³ (5.8 L) 351 had a 4.56 in (115.824 mm) bore and 3.58 in stroke (90.9 mm). It was basically an enlarged 305. In 1972, the 351 was replaced by a 379.
[edit] 379
The 379 in³ (6.2 L) 379 had a 4.562 in (115.875 mm) bore and 3.86 in stroke (98 mm).
[edit] 401
The engine was further enlarged for the 401 in³ (6.6 L) 401.It has a 4.87 in (123.7 mm) bore and 3.58 in stroke (90.9 mm). this engine was used in the 67 model
[edit] 432
In late production there was also a 432 in³ (7.1 L) version with enlarged crankshaft journals.
[edit] 478
The 477.7 in³ (7.8 L) 478 was one of the largest V6 engines ever built. Gross output was 235 hp (175 kW) at 3200 rpm and 440 ft.lbf (597 Nm) at 1400 rpm. Bore was 5.125 in (130.2 mm) and stroke was 3.86 in (98 mm). It was introduced in 1963 in the 6500 series trucks.
It was superseded by the 1966 478M "Magnum" series, and production ended by 1974. Gross output was now 254 hp (189 kW) at 3700 rpm and 442 ft.lbf (599 Nm) at 1400 rpm.
[edit] 702
The massive 702 in³ (11.5 L) V12 "Twin Six" was offered in United States GMC commercial trucks, and as a special order option in Canada. It was often mistaken as two lesser V-Six engines welded together but in fact was one massive casting. It used two separate exhaust manifolds, two separate distributors caps driven off of a single distributor drive, and other parts from the 351. 56 major parts are interchangeable between the Twin-Six and the other GMC V-6 engines to provide greater parts availability and standardization. It produced 250 net SAE horsepower (190 kW). Torque was 585 lbf·ft (793 N·m). More information can be found at http://www.6066gmcguy.org/Jolly-702v12.htm
