Well, we will see how this works. I have tried modifying a vacuum operated valve so that a cable can operate it. Pictures attached tell the story.
 
1. Opened_heater_valve3.jpg shows the result after I took a 1" hole saw to the heater valve. Pretty much ruined it, but I could then see how it works. There is a spring to hold the valve closed, and the diaphram pulls the valve open when vacuum is applied.
 
2. I then bought another one, and carefully drilled a 5/16" hole in the center, as shown in Heater_valve_smhole.jpg .  The pin lying by its side has been tapped for 10-32 on one end, and drilled for a push fit on the other.
 
3. The pin has been 'JB-welded' to the pin on the diaphram, and we shall see how well this stands up.
 
Picture of 3 on next email to stay below limit.
Bill Schertz
KIS Cruiser # 4045