Heron Pistons and Larger Valves

[JShadzi at aol.com]

In a message dated Tue, 19 Dec 2000 12:37:30 PM Eastern Standard Time, DeWitt 
Harrison <de at aztek-eng.com> writes:

<< 
<<I'm curious about what is meant by "unshrouding" the valves inthe context 
of head work. I've come across this term before where there can be a 
shrouding effect due to the close proximity of the valve to the cylinder wall 
which then acts as an impediment to flow. But this seems different. Please 
fill me in. >>

   Unshrouding a valve is reducing its close proximity to the side of the 
combustion chamber.  Thus, if you have a valve that opens to a certain lift, 
its flow will be impeded if the side of the combustion chamber is to close 
the the opening of the valve.  Material can be removed in the area around the 
valve (in the combustion chamber) to allow air to flow from all 360 degrees 
of the valve opening, and effectively making the combustion chamber larger 
which will reduce compression ratio.
Javad