Engines

What is taper and ovality in the bore, how is it caused how do you check it?
Taper is a decrease in diameter from one end to the other.  for example when the piston hits against the bore continuesly changes the shape to oval. 



What is side clearance on a piston and how is it checked? 
Side clearance is the gap between the cylinder bore and the piston.

How can you tell the difference between a inlet and exhaust vavle and why?
The inlet valve is much bigger than the exhaust valve and that is because its job is to suck in as much air  as it can.



What sort of tempatures do the inlet and exhaust valves get upto?
The inlet temp is 250 degrees and exhaust is 750 degrees.

What temperatures and speeds must the piston be able to cope with?
The piston should be able to get up to 300 degrees and a speed of 30 metres per second.


Why do we have piston ring end gap clearance ?
The reason for this is so that the it allows carbon in so it can push the rings against the bore for better compression.



What could the result be if the piston ring end gap is too small?
The ends of the rings will touch when the engine heats up this can damage the cylinder walls.



Why do aluminum cylinder heads usually have a steel shim (washer) between the valve spring and the 
cylinder head surface ?
Thats because the aluminium is not strong enough on its own therefore by having the steel it will help not warn the head when it hits. 

What is meant by the terms S.I and C.I in a four stroke engine?
SPARK ignition and COMPRESSION ignition.  
What is the purpose of the margin on the valve?