Big blockblock11/22/2023 It had a dry weight of approximately 665 pounds (302 kg), depending on the type of intake manifold and carburetion systems present. The W-series was a physically massive engine when compared to the "Small Block" Chevrolet engine. 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 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. The spark plugs were inserted vertically into the quench area, which helped to produce a rapidly moving flame front for more complete combustion. 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. 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. 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. 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 push rods also acted as conduits for oil flow to the valve gear. 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.Īs 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. 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. The engine block 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. The W-series engine was made of cast iron.
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