Engine Blocks

Just as construction of a building begins with a foundation, assembly of an engine starts with the block. Major components like the crankshaft, pistons and cylinder head(s) are installed on the block, and the block is usually where the motor mounts are installed that attach the block to the vehicle chassis. Engine blocks used to be predominately made of cast iron, but today most vehicles have aluminum blocks with cast iron cylinder liners.

Engine blocks are most commonly identified by their cylinder configuration. In-line engines have the cylinders next to one another in a row. 3, 4, 5, and 6-cylinder in-line engines are common, but years ago many vehicles came with “straight 8s”. V-type engines allow multiple cylinders to be assembled in a much more compact package, with an equal number of cylinders in each bank. The angle of the V is usually (but not always) 90-degrees and there can be anywhere from 6 to 12 cylinders in a modern V-type engine. In the past some Ford and Lancia vehicles were equipped with V4 engines, and in the 1930s luxury vehicles like Cadillac and Marmon came with massive V16 engines. Less common are horizontally opposed “flat” engines, where 2 or 3 cylinders are arranged on either side of the crankshaft. This configuration was famously used in the Volkswagen Beetle but has also been used extensively by Porsche and Subaru.

After an engine block is cast it undergoes extensive machining so other components can be properly installed. The oil pan rails, block deck and other surfaces are machined smooth for proper gasket sealing. The bores for the crankshaft (and camshaft on overhead valve engines) are machined to allow the installation of plain bearings. All the required attachment holes are drilled/tapped to accept fasteners. The block is bored 90 degrees to the crankshaft centerline and honed to the finish required for optimal piston ring seating. When an engine is remanufactured it is common to bore/hone the cylinders, resurface the block deck, and align hone the main bearing saddles.

Engine blocks also include an extensive network of coolant and oil passages. The oil pump usually bolts to the block and passages are necessary to carry oil under pressure to the crankshaft and camshaft bearings and to the cylinder head so the valvetrain can be lubricated. There are also paths for the oil to drain back to the oil pan. The collection of passages cast into the block for coolant flow is known as the “water jacket”. Coolant is drawn from the radiator by the water pump and circulated through the block and heads, absorbing heat from the cylinders and combustion chambers. It then flows out through the top radiator hose back to the radiator where it is cooled. Holes made in the block to facilitate the casting process are sealed by core plugs.

Aftermarket engine block makers analyze the factory product and they know the weaknesses and where improvements can be made. As a result, you can get blocks made with more material to prevent bore distortion and maintain head gasket seal, and billet steel splayed 4-bolt main caps for greater strength. Performance blocks are available with larger water jackets for improved coolant circulation and re-engineered oil galleries and oil feed holes to increase oil flow. Perhaps the best motive for using an aftermarket block is that your engine can be made so much larger. When it comes to making horsepower, there’s no substitute for cubic inches, but the meat in a factory block can limit the size of an overbore, and there may not be enough room inside the crankcase for a substantial increase in stroke. Aftermarket blocks have more material for increased bore size, and some even have larger bore spacing. Blocks are available with the cam located higher up in the block to clear a stroker crank. You can build an engine with far greater displacement that’s still the same physical size.