Cylinder adaptations for screwed-in valve guides
 		  
This picture of a cylinder shows the exhaust valve stem guiding bore. When adapting the cylinder to take an exchangable screwed-in guide, the protuding part of the old guide should be cut-off before drilling of the valve stem bore is carried out.
 
 
This Figure shows the adaptations for centred fitting (see text) of the screwed-in guide, based on the guide TRW 81-2696. The screw thread  selected is spark plug thread (14x1.25 mm) for providing optimal wall thickness proportions of the guide and the remaining cylinder material around the guide bore.   
(The small screw for locking the valve guide is not shown). 
 
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