What are Rocker Arms & what
do they do?
| The rocker is a small part of the engine, between the cam and
the top of the valves in the "head" of the engine, when the cam (see cams)
runs over them, it opens the valves |
A rocker arm for an over head cam 16 valve |
| Even crank cams have rockers, and usually have tappets to check and
set at the head of an engine, these are pushed by push rods |
No Photo as yet
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What are tappets and what do they
do?:
Tappets there is a small, but essential part of the engine, it
is the screw & nut, which runs through the right hand side of the rocker
(see above).
The amount of thread, showing below the rocker must be very precise,
as this is where you get the valve tolerance.
Too tight and the rocker will snap, or the valve can either hit
the piston, or you will lose compression. You want to avoid both! |
Circled in white: the locking screw
|
circled in white: the locking nut
Both together the comprise the tappet.
|
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SEE ALSO Bucket and Shims - page not yet built.
What are Valves & what do they
do?:
When valves are closed, They have to be air tight when the piston comes
to Top Dead Center, so that compression is kept. when the piston on it's
compression stroke (coming up when both valves closed), containing the
fuel/air mixture, which you want for better bangs, you want all that bang
contained in the chamber, not leaking anywhere, so the all the force is
transferred into pushing the piston back down.
You can use compression due to leaking head gaskets, valve seats,
valves them selves as well as loose fitting spark plugs, not just through
bores, piston rings pistons. |
The top two exhaust valves (closed)
the lower two inlet valves (closed)
|
When the valves are pushed down, on an inlet stroke, they open
to allow fuel get into the combustion chamber.
At this time, the pistons are going down the bore and sucking
the air/fuel mixture
See also carburetors |
No Photo's as yet
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When the valves are pushed down, on an exhaust stroke, they allow exhaust
gasses out through to the exhaust.
At this time the piston(s) are coming up the bore and pushing
the exhaust gasses out of the combustion changer, when it reaches just
before top dead center, the valve closes, before going down, the inlet
valve opens and the cycle starts again |
No Photo's as yet
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