383 CRATE ENGINE
383 crate engine is a factory made Chevy stroker motor replacement engine. It comes complete with intake manifold, and carburetor or fuel injection system and an alternator. The engine is custom built with special specifications. The most common reason for engine replacement is to increase the power of the car. Racing car engines are often changed to increase their speed and power. Other motorists replace their engines for a more powerful one just for the thrill of high speeds.
The power of the engine is increased by increasing the length of the stroke of the piston. The stroke is the vertical distance moved by the piston in the cylinder. It is the distance between the top dead center of the piston and its bottom dead center. This translates into a higher volume available for the fuel-air mixture required for combustion. The replacement engine therefore has a higher cc capacity and produces higher power. High stroke engines make higher power with low revolutions per minute. The torque, which is a low revolution power, is increased by increasing stroke and enabling the car to have this power without having to install a larger and heavier engine. Chevy 383 crate engine has a capcity of 383 cubic inch.
The stroke is increased by increasing the height of the vertical motion of the crankshaft rod journals. The journals are eccentric to the centerline. The piston moves higher in the cylinder if the length the journal is increased. The length of the journal may be increased by offset grinding thereby moving the centerline of the rod journal towards that of the main journal. This increases stroke. The journal will now have a smaller diameter and the connecting rods have to be replaced. Too much grinding will make the rod journal weak.
The increase in stroke creates a high degree of piston rod angularity. This has to be corrected by using longer piston rods. Longer piston rods are also necessary to prevent the piston from being pulled out of the bottom of the cylinder. Rod ratio is the ratio of the rod length to the stroke. It is a measure of rod angularity. The rod angularity is high at a low rod ratio. At a high rod ratio the rod tends to drive the piston into the walls of the cylinder resulting into accelerated wear of the piston rings and cylinder linings. A ratio of 1.5:1 is the lowest recommended road ratio and ratios between 1.65:1 – 1.80:1 are ideal and are used in 383 crate engine.