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I did a search but didn't really find exactly what I was looking for. I have a 77 with the vacuum operated heat riser valve. My question is when vacuum is applied is it opening it or closing it? If it is closing it, it seems to stay closed even with the engine up to operating temp. I live in Texas & the car never gets driven when the temps are cold. So I would really like to have it just open all the time. Thanks in advance.
Engine Cold (below 180*) vacuum passes through the EFE TVS switch to actuator.
Engine above 180* EFE TVS switch shuts off vacuum path to the actuator
Actuator exhausts energy through the exhaust port of the EFE TVS switch...
So Yes, vacuum closes the heat riser valve.
Maybe your TVS switch is not closing, or exhausting at or around the 180* mark?
The switch needs to exhaust so the actuator can return to it Home or "OPEN" position.
The positions of the Heat Riser Valve
Left photo Engine Temp Below 180*
Right photo Engine Temp at or above 180*
Notice the finger stops in relation as to valve open or closed...
The valve should fail-open, with no vacuum applied, Armed with @bmotojoe's great photos, you can easily confirm this. With a Mity-Vac, you can test that the valve still closes with a vacuum applied, and use the gauge to test for vacuum elsewhere, like through that TVS, for example.
Ok so with no vacuum the valve is open. The valve is working fine, I think the switch is not ever shutting off the vacuum once the engine gets up to operating temp. I would like for it to just stay open all the time. I inserted a plug in the vacuum hose & reconnected it to the vacuum actuator. The reason I did it this way is because it has to look operational as this is a very low mileage all stock car. Eventually I guess I should get a new vacuum switch. Thanks for all the responses
if you want it to look original, epoxy up the port in the TVS valve and hook the hoses back up. make sure the valve is open. if you really want it to appear orig, take the heat riser off and remove the flapper. then it can cycle or hang up in the wrong place and not affect the way the engine runs or heats up the carb like you are in minnesota in winter...
if you want it to look original, epoxy up the port in the TVS valve and hook the hoses back up. make sure the valve is open. if you really want it to appear orig, take the heat riser off and remove the flapper. then it can cycle or hang up in the wrong place and not affect the way the engine runs or heats up the carb like you are in minnesota in winter...
That is essentially what I did except I inserted a small rubber vacuum cap inside the vacuum line to plug it & then reinserted the line back on the vacuum can.
There was a similar thread where the OP said valve wouldn't open. Was suggested he install a 195 degree thermostat instead of the 180 that was likley in it and see what happens. In that guys case, it worked.
1977 heat riser valve
