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The L72 was a 427 cu in (7.0 L) 90° overhead valve V8 big-block engine produced by Chevrolet between 1966 and 1969. Initially rated at 450 horsepower, the rating dropped to 425 hp (317 kW) shortly after its release (although there was no change in power).
In all forms (except the aluminum ZL-1), the Mark IV was slightly heavier than the W-series model, with a dry weight of about 685 lb (311 kg). Aside from the new cylinder head design and the reversion to a conventional 90 degree cylinder head deck angle, the Mark IV shared many dimensional and mechanical design features with the W-series engine.
The L78 was a Big-Block engine produced by Chevrolet between 1965 and 1970. Rated at 425 hp (317 kW) for its first year, the rating dropped to 375 hp (280 kW) in subsequent years (although there was no change in power).
Also called the GM small corporate pattern and the S10 pattern. This pattern has a distinctive odd-sided hexagonal shape. Rear wheel drive applications have the starter mounted on the right side of the block (when viewed from the flywheel) and on the opposite side of the block compared to front wheel drive installations.
This reduces repair costs as a single failed head on a single cylinder can be changed instead of a larger, much more expensive unit fitting all the cylinders. Such a design also allows engine manufacturers to easily produce a 'family' of engines of different layouts and/or cylinder numbers without requiring new cylinder head designs.
Overheating was a serious concern for the engine, since the engine block was of an open-deck design, severe overheating could cause the cylinder barrels to warp and pull away from the head gasket, causing coolant leaks into the cylinders and cylinder scuffing. Maintaining oil and coolant levels was crucial for the engine.
Cylinder head porting refers to the process of modifying the intake and exhaust ports of an internal combustion engine to improve their air flow. Cylinder heads, as manufactured, are usually suboptimal for racing applications due to being designed for maximum durability. Ports can be modified for maximum power, minimum fuel consumption, or a ...
Starting around 1925 engine blocks and cylinder heads were now developed at each brand but were cast at Saginaw Metal Casting Operations. [3] In the mid-1960s, there were 8 separate families of GM V8 engines on sale in the USA. [4] [1] By the 1970s, GM began to see problems with their approach.