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Chevrolet big-block engine
The Chevrolet big-block engine is a series of large-displacement, naturally-aspirated, 90°, overhead valve, gasoline-powered, V8 engines that was developed and have been produced by the Chevrolet Division of General Motors from the late 1950s until present. They have powered countless General Motors products, not just Chevrolets, and have been used in a variety of cars from other manufacturers as well - from boats to motorhomes to armored vehicles.
Chevrolet had introduced its popular small-block V8 in 1955, but needed something larger to power its medium duty trucks and the heavier cars that were on the drawing board. The big-block, which debuted in 1958 at 348 cu in (5.7 L), was built in standard displacements up to 496 cu in (8.1 L), with aftermarket crate engines sold by Chevrolet exceeding 500 cu in (8.2 L).
The first version of the "big-block" V8 Chevrolet engine, known as the W-series, was introduced in 1958. Designed for use in passenger cars and light trucks, the cast iron block, overhead valve engine had offset valves and uniquely scalloped valve covers, giving it a distinctive appearance.
The W-series was produced from 1958 to 1965, in three displacements:
The engine had 4.84-inch (123 mm) bore centers, two-bolt main bearing caps, a "side oiling" lubrication system (the main oil gallery located low on the driver's side of the crankcase), with full-flow oil filter, and interchangeable cylinder heads. Heads used on the high performance 409 and 427 engines had larger ports and valves than those used on the 348 and the base 409 passenger car and truck engines, but externally were identical to the standard units – but for the location of the engine oil dipstick, on the driver's side on the 348 and the passenger's on the 409/427. No satisfactory explanation was ever offered for why this change was made, but it did provide a reliable means of distinguishing a 348 from the larger engines.
As with the 265 and 283 cu in (4.3 and 4.6 L) "small-block" engines, the W-series valve gear consisted of tubular steel pushrods operating stud-mounted, stamped-steel rocker arms. The push rods also acted as conduits for oil flow to the valve gear. Due to the relatively low mass of the valve train, mechanical lifter versions of the W-series engine were capable of operating at speeds well beyond 6000 rpm.
The combustion chamber of the W-series engine was in the upper part of the cylinder, not the head, the head having only tiny recesses for the valves. This arrangement was achieved by combining a cylinder head deck that was not perpendicular to the bore with a crowned piston, which was a novel concept in American production engines of the day. As the piston approached top dead center, the angle of the crown combined with that of the head deck to form a wedge-shaped combustion chamber with a pronounced quench area. The spark plugs were inserted vertically into the quench area, which helped to produce a rapidly moving flame front for more complete combustion.
The theory behind this sort of arrangement is that maximum brake mean effective pressure (BMEP) is developed at relatively low engine speeds, resulting in an engine with a broad torque curve. With its relatively flat torque characteristics, the "W" engine was well-suited to propelling both the trucks and heavier cars that were in vogue in the US at the time. The W-series was a physically massive engine when compared to the "small-block" Chevrolet engine. It had a dry weight of approximately 665 pounds (302 kg), depending on the type of intake manifold and carburetion systems present. It was 1.5 inches longer, 2.6 inches wider, and 0.84 inches shorter than the 283 "small-block".
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Chevrolet big-block engine
The Chevrolet big-block engine is a series of large-displacement, naturally-aspirated, 90°, overhead valve, gasoline-powered, V8 engines that was developed and have been produced by the Chevrolet Division of General Motors from the late 1950s until present. They have powered countless General Motors products, not just Chevrolets, and have been used in a variety of cars from other manufacturers as well - from boats to motorhomes to armored vehicles.
Chevrolet had introduced its popular small-block V8 in 1955, but needed something larger to power its medium duty trucks and the heavier cars that were on the drawing board. The big-block, which debuted in 1958 at 348 cu in (5.7 L), was built in standard displacements up to 496 cu in (8.1 L), with aftermarket crate engines sold by Chevrolet exceeding 500 cu in (8.2 L).
The first version of the "big-block" V8 Chevrolet engine, known as the W-series, was introduced in 1958. Designed for use in passenger cars and light trucks, the cast iron block, overhead valve engine had offset valves and uniquely scalloped valve covers, giving it a distinctive appearance.
The W-series was produced from 1958 to 1965, in three displacements:
The engine had 4.84-inch (123 mm) bore centers, two-bolt main bearing caps, a "side oiling" lubrication system (the main oil gallery located low on the driver's side of the crankcase), with full-flow oil filter, and interchangeable cylinder heads. Heads used on the high performance 409 and 427 engines had larger ports and valves than those used on the 348 and the base 409 passenger car and truck engines, but externally were identical to the standard units – but for the location of the engine oil dipstick, on the driver's side on the 348 and the passenger's on the 409/427. No satisfactory explanation was ever offered for why this change was made, but it did provide a reliable means of distinguishing a 348 from the larger engines.
As with the 265 and 283 cu in (4.3 and 4.6 L) "small-block" engines, the W-series valve gear consisted of tubular steel pushrods operating stud-mounted, stamped-steel rocker arms. The push rods also acted as conduits for oil flow to the valve gear. Due to the relatively low mass of the valve train, mechanical lifter versions of the W-series engine were capable of operating at speeds well beyond 6000 rpm.
The combustion chamber of the W-series engine was in the upper part of the cylinder, not the head, the head having only tiny recesses for the valves. This arrangement was achieved by combining a cylinder head deck that was not perpendicular to the bore with a crowned piston, which was a novel concept in American production engines of the day. As the piston approached top dead center, the angle of the crown combined with that of the head deck to form a wedge-shaped combustion chamber with a pronounced quench area. The spark plugs were inserted vertically into the quench area, which helped to produce a rapidly moving flame front for more complete combustion.
The theory behind this sort of arrangement is that maximum brake mean effective pressure (BMEP) is developed at relatively low engine speeds, resulting in an engine with a broad torque curve. With its relatively flat torque characteristics, the "W" engine was well-suited to propelling both the trucks and heavier cars that were in vogue in the US at the time. The W-series was a physically massive engine when compared to the "small-block" Chevrolet engine. It had a dry weight of approximately 665 pounds (302 kg), depending on the type of intake manifold and carburetion systems present. It was 1.5 inches longer, 2.6 inches wider, and 0.84 inches shorter than the 283 "small-block".