Page 5 - E BOOK ENGINE MECHANICAL M2

1. TECHNICAL FEATURES OF 4B1 ENGINE

2. FEATURES OF COMPOSING PARTS
(1) Cylinder Head

Fig. 1-2

The cylinder head is made of an aluminum alloy, which is lightweight and offers a high level of cooling
efficiency. The combustion chamber is a pent-roof design with a centered spark plug. This permits a
small valve compound angle to realize a compact chamber.
Two each, cross-flow type inlet and exhaust ports are provided independently on the right and left
sides of the cylinder head. The camshafts are held by five camshaft bearings at the inlet and ex-
haust sides. The No. 4 bearing sustains the thrust load of the camshafts. Only the No. 1 bearing uses
a bearing cap that integrates both the inlet and exhaust camshafts.

(2) Cylinder Block
The cylinder block is made of an aluminum alloy for
weight reduction, and to increase the wear resistance of
the cylinder wall, a steel cylinder liner is press-fitted into
the cylinder .
5 bearings are provided for the crankshaft journals and
the No. 3 bearing sustains the thrust load of the crank-
shaft.
The water jacket is the full Siamese type where the
cylinder bores are attached to each other and a coolant
passageway is not provided between bores as shown
here.

Fig. 1-3

An oil jet is provided in front of the cylinder block to sup-
ply engine oil to the timing chain.

A ladder frame is also made of an aluminum alloy, how-
ever the bearing caps are made of forged steel.

1 - 2 Pub. No. PTAE1225