GMC V6 engine
Encyclopedia
GMC Truck produced a unique 60° V6 engine
from 1960 through 1978. The engine was available in 305, 351, 401 and 478-cubic-inch (5.0, 5.8, 6.6, and 7.8 L) versions. In late production there was also a 432 CID version with enlarged crankshaft journals. GMC also made a 637 CID 60° V8
with twin balance shaft
s using the same general layout as the 305. Finally, there was a 702 CID "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.
engine for GMC from 1960 to 1966, and was one of the first V6 engines produced by an American company.
In 1972, the 351 was replaced by a 379.
It was superseded by the 1966 478M "Magnum" series, and production ended by 1974. Gross output was now 254 hp at 3700 rpm and 442 ft.lbf (599 Nm) at 1400 rpm.
"Twin Six" was offered in United States
GMC commercial trucks, and as a special order option in Canada
. It was often mistaken as two V6 engines welded together but in fact was a single casting. It used four separate exhaust manifold
s, two separate carburetor
s, two separate distributor
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 lbft.
V6 engine
A V6 engine is a V engine with six cylinders mounted on the crankcase in two banks of three cylinders, usually set at either a right angle or an acute angle to each other, with all six pistons driving a common crankshaft...
from 1960 through 1978. The engine was available in 305, 351, 401 and 478-cubic-inch (5.0, 5.8, 6.6, and 7.8 L) versions. In late production there was also a 432 CID version with enlarged crankshaft journals. GMC also made a 637 CID 60° V8
V8 engine
A V8 engine is a V engine with eight cylinders mounted on the crankcase in two banks of four cylinders, in most cases set at a right angle to each other but sometimes at a narrower angle, with all eight pistons driving a common crankshaft....
with twin balance shaft
Balance shaft
In piston engine engineering, a balance shaft is an eccentric weighted shaft which offsets vibrations in engine designs that are not inherently balanced...
s using the same general layout as the 305. Finally, there was a 702 CID "Twin Six" V12
V12 engine
A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft....
, which was basically two 351s placed end-to-end with a common block and crank. A Diesel
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...
version was called the ToroFlow.
305
The 305 CID 305 had a 4.25 in (108 mm) bore and 3.58 in stroke (90.9 mm). The 305 V6 was the standard pickup truckPickup truck
A pickup truck is a light motor vehicle with an open-top rear cargo area .-Definition:...
engine for GMC from 1960 to 1966, and was one of the first V6 engines produced by an American company.
351
The 351 CID 351 had a 4.56 in (115.8 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.
379
The 379 CID 379 had a 4.562 in (115.9 mm) bore and 3.86 in stroke (98 mm).401
The engine was further enlarged for the 401 CID 401.It has a 4.87 in (123.7 mm) bore and 3.58 in stroke (90.9 mm).432
In late production there was also a 432 CID version with enlarged crankshaft journals (bore 4.875", stroke 3.859").478
The 477.7 CID 478 was one of the largest V6 engines ever built. Gross output was 235 hp 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 at 3700 rpm and 442 ft.lbf (599 Nm) at 1400 rpm.
702
The 702 CID V12V12 engine
A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft....
"Twin Six" was offered in United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
GMC commercial trucks, and as a special order option in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. It was often mistaken as two V6 engines welded together but in fact was a single casting. It used four separate exhaust manifold
Exhaust manifold
In automotive engineering, an exhaust manifold collects the exhaust gases from multiple cylinders into one pipe. The word manifold comes from the Old English word manigfeald and refers to the folding together of multiple inputs and outputs.In contrast, an inlet manifold is the part of an engine...
s, two separate carburetor
Carburetor
A carburetor , carburettor, or carburetter is a device that blends air and fuel for an internal combustion engine. It is sometimes shortened to carb in North America and the United Kingdom....
s, two separate distributor
Distributor
A distributor is a device in the ignition system of an internal combustion engine that routes high voltage from the ignition coil to the spark plugs in the correct firing order. The first reliable battery operated ignition was developed by Dayton Engineering Laboratories Co. and introduced in the...
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 lbft.