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I have a 77 with the vacuum operated heat riser valve. My question is when no vacuum is applied is the valve open or closed. I want to permently keep it open but don't know which way to go. Thanks in advance.
Sorry seems like after reviewing my posts, I have asked this question before. My bad.
If you didn't find a answer reviewing your posts here is a photo showing the valve open & closed...
And a little explanation of how the circuit works...
If you zoom in on what I'll call the stop finger, you can then see what position the flap is in...
The stop finger is connected to the actuator via shaft...
Note: On a cold start Vacuum passes through the EFE TVS (Themo Vacuum Switch) to actuator, the actuator then closes the Heat Riser...
After Engine temp reaches about 180* the TVS switch changes state blocking vacuum to actuator, you will notice the TVS switch has what looks like a open 3rd port. That is an exhaust port...
If the circuit is working properly the normal state of the actuator and heat riser valve is OPEN...
But they have been known to freeze up in the closed position...
And consider doing what the author of that thread did, cut out the flap, and block the side holes. Whatever you do, please post some photos to help the next person with this question!
Heat riser valve
