A car engine consists of core components, including the engine block, pistons, crankshaft, camshaft, and valves, which turn fuel into mechanical power through combustion.
The engine system is actually made of three subsystems. Engine Top End, Engine Bottom End and Engine Front End.
These parts are supported by essential subsystems—lubrication, cooling, fuel, and ignition—that ensure smooth operation, optimal temperatures, and precise combustion timing.
The engine top end can be either OHV or OHC.
Engine Top End
- Cylinder Head. It bolts to the deck of the block and covers the top of the cylinders. A head gasket seals the block and head surfaces to prevent oil, coolant, and pressure leakage.
- Bare Cylinder Head. It is a head casting, with all of its parts removed. The cylinder head consists of combustion chambers, intakes ports, exhaust ports, oil passages, water jackets, intake deck, exhaust deck, and dowel holes.
- Valve Guides. There are small holes machined through the top of the head, into the intake and exhaust ports. The two basic types of valve guides are the integral and pressed-in.
- Valve Seats. They are round, machined surfaces in the port openings to the combustion chambers. The valve seats can be part of the head or a separated pressed-in component.
- Valves. Open and close to control flow in and out of the combustion chamber.
- Valve Seals. They prevent oil from entering the cylinder head ports through the valve guides.
- Valve Spring: It is used to close the valve. It basically consists of a valve spring, retainer, and two keepers.
- Camshaft. It opens the engine valves at the right time during each stroke.
- Valve Lifters. Also called tappets, ride on the cam lobes and transfer motion to the rest of the valve train.
- Push Rods. Transfer motion between the lifters and the rocker arms. They are needed when the camshaft is located in the cylinder block
- Rocker Arms. Transfer motion from the push rods to the valves. They can be used in both OHC and OHV engines. The rockers mount on top of the cylinder head by various methods; rocker shaft, rocker stud, or rocker pedestal. There are two types of rocker arms; adjustable, and non adjustable. Adjustable rocker arms provide a means of changing valve train clearance or lash.