Mazda Training manual - part 246

 

  Index      Mazda     Mazda Training Manual

 

Search            

 

 

 

 

 

 

 

 

 

Content   ..  244  245  246  247   ..

 

 

Mazda Training manual - part 246

 

 

 
4 – VALVE TRAIN 

 

69

Piston Engine Fundamentals

TC010-05-01S

PUSHRODS (OHV)

 

 
In an OHV engine, pushrods transfer the lifting motion from the camshaft 
and lifters to the valves. Pushrods are made of stiff steel tubing, with cups 
or balls on the ends to mate with the lifters and rocker arms. 
 
The pushrods flex slightly in normal operation, and this flexing is taken into 
account when the cam lift is designed. On some engines, pushrods come 
in varying lengths to provide an initial clearance adjustment with hydraulic 
lifters. 
 
 
 
ROCKER ARMS

 

 
The rocker arm reverses the direction of lift from the pushrod or camshaft 
to the valve. Mazda engines use shaft-pivoted rocker arms, as shown in 
Figure 50. The rocker arm is made of aluminum, and a pivot is drilled out 
so the rocker arm can run on a hollow rocker arm shaft. 

 

 

 
 
 
 
 
 
 
 
 
 
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FIGURE 50. 
Rocker arms are 
fitted to shafts.

 

 

Rocker arm 
shaft 

Shaft-pivote
d rocker arm 

Valve 

Pushrod 

 

 
4 – VALVE TRAIN 

 

70

Piston Engine Fundamentals

TC010-05-01S

REVIEW EXERCISE 6

 

 
Fill in the words that correctly complete these sentences. Check your answers with the 
answer key on page 73.

 

 
1.      The space between the end of the valve stem and the rocker arm is called 

_________________________________. 

 
2.   A(n) __________________ uses oil pressure and a plunger to eliminate the need for 

manual valve adjustments. 

 
3.   In an OHV engine, the ______________________ transfers the lifting motion from the 

camshaft and lifters to the valves. 

 
4.   A ___________________________ changes the direction of pushrod or camshaft 

motion. 

 
5.      A ticking noise from the top of the engine at one half crankshaft speed may be caused 

by: 

 

A.  excessive valve clearance 
B.  worn cylinders   
C.  a clogged HLA   
D.  carbon build-up 

 
 
 

 
5 – LUBRICATION SYSTEM 

 

71

Piston Engine Fundamentals

TC010-05-01S

The lubrication system provides a steady supply of pressurized oil to the moving parts of 
the engine. Lubrication reduces friction and keeps parts from wearing against each other. 
Oil also helps cool, clean, and reduce noise by constantly recirculating the engine oil 
through an external filter. This section describes how the lubrication system works. 
 
 
 
OBJECTIVES

 

 
 
After completing this section, you will be able to: 
 
• 

Identify important parts of the lubrication system and describe how they operate. 

 
• 

Describe how oil flows through the lubrication system. 

 
• 

Describe the differences between rotor-type and gear-type oil pumps. 

 
• 

Describe how the oil filter traps dirt and debris in the oil. 

 
• 

Describe the materials used in oil seals and gaskets. 

 
5 – LUBRICATION SYSTEM 

 

72

Piston Engine Fundamentals

TC010-05-01S

 
 
 
 
 
 
FIGURE 51. The 
lubrication 
system provides 
a steady supply 
of pressurized 
oil to moving 
engine parts. 

 
 

Oil pan

 

Oil strainer

 

Oil pump

 

Oil filter

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

SYSTEM COMPONENTS

 

 
Some important parts of the lubrication system are shown in Figure 51. 
These parts are described in the following paragraphs. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Content   ..  244  245  246  247   ..