Automobile engines are classified into four categories according to the arrangement of inlet and exhaust valves in various positions in the cylinder head or block. These arrangements are termed as L”I’ ‘F’, and ‘T’. It is easy to remember the word ‘LIFT’ to recall the four-valve arrangements. The I-head design is most commonly used in automobile engines.
The cylinder head is classified into five categories with respect to Valve fitting this is also under:-
- I-Head Engine.
- L-Head Engine.
- F-Head Engine.
- T-Head Engine.
I-head engine. In the I-head or overhead valve engine, the valves are located in the cylinder head. In-line engines usually have the valves in a single row. V-8 engines may have the valves in a single row or in a double row in each bank. Regardless of the arrangement, a single camshaft actuates all the valves.
In most engines, the camshaft is fitted in the cylinder block while some engines employ an overhead camshaft run with the help of a timing Chain and timing belt this system is mostly used in the automobile as both the valve are most effective in this position.
In an L-head arrangement, the inlet and exhaust valves are located side by side and operated by a single camshaft. The combustion chamber and cylinder form an inverted L. All the valves for an engine are arranged in one line, except for V-8 L-head engines, which are in two lines. In L-head engines, the valve mechanisms are in the block and hence the cylinder head may be easily removed when required for overhauling the engine. Although L-head engines are rugged and dependable, they are not particularly adapted to higher compression.
The I-head valve engine is more adaptable to a higher compression ratio. In the I-head valve engine, the clearance volume can be reduced to a greater amount than in the L-head engine. In some I-head engines, there are pockets in the piston heads no which the valve can move when they are open with the piston at T.D.C.
This engine is a combination of L-head and I-head engines, in which one valve usually an inlet valve is in the head and the exhaust valve is in the cylinder block. Both sets are driven from the same camshaft.
While the exhaust valve fitted in the block is active directly e-bike camshaft by Tapit this system is not very commonly used as gases get pocketed over this area and homogeneous burning of gases cannot be achieved this system is used in the petrol Jeep.
The t-head engine has the inlet valves on one side and the exhaust valves on the other side of the cylinder. Thus, two camshafts are required to operate them.