Heat riser control ???
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Laughing Gas
Joined: Aug 2010
Posts: 983
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From: Northern Kentucky
Heat riser control ???
On my '84 f150 351W, I have a yellow 3 port temperature sensitive Vacuum Control Valve (VCV) that controls the heat riser on the exhaust manifold.
The problem is that it does not seem to be functioning correctly. It will close the heat riser when cold but it doesn't open it up properly.
Either the valve is bad or the temperature is not getting hot enough to open it due to a bad thermostat. My heat gauge reads rather low but they are notoriously poor and I seem to have enough heat from the heater.
Does anyone know the temperature at which these yellow 3 port valves should open?
The problem is that it does not seem to be functioning correctly. It will close the heat riser when cold but it doesn't open it up properly.
Either the valve is bad or the temperature is not getting hot enough to open it due to a bad thermostat. My heat gauge reads rather low but they are notoriously poor and I seem to have enough heat from the heater.
Does anyone know the temperature at which these yellow 3 port valves should open?
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Joined: Jan 2001
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From: Virginia
Somewhere around 100 degrees water temp. Try swapping the lines to the valve. The line going to the heat valve diaphragm needs to exhaust itself when the water temp valve finally closes. If you have the input port and the output port mixed up, it will apply vacuum to the exhaust valve, but will not release the vacuum properly.
Thread Starter
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Laughing Gas
Joined: Aug 2010
Posts: 983
Likes: 49
From: Northern Kentucky
Tried swapping ports but the other port doesn't apply vacuum when the engine is cold. The other port is plugged because it was used to control some other emission solenoids that are now gone.
If I remove the plug from the other port, the valve will then exhaust at 100 deg. but wouldn't I then have a vacuum leak when it switched to that port?
Any suggestions on how to get around this?
If I remove the plug from the other port, the valve will then exhaust at 100 deg. but wouldn't I then have a vacuum leak when it switched to that port?
Any suggestions on how to get around this?
Thread Starter
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Laughing Gas
Joined: Aug 2010
Posts: 983
Likes: 49
From: Northern Kentucky
Will try to post a picture as soon as the wife's camera charges up. until then maybe a description/diagram might help. This what the rad. support label shows:
|---> top port to lines eventually terminating at manifold vacuum tree
|---> center port to heat valve
|---> bottom port to solenoid valves that control EGR (EGRC/EGRV I think)
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this is how I have it now:
|---> top port to manifold vacuum tree
|---> Center port to heat valve
|---> bottom port plugged
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|
Hope this helps 'til I can get a picture!
Just to be clear, this truck has been converted from feedback carb./TFI ign. to std carb./DS II ign. and the computer and all computer controlled emissions equipment were removed (only the cat. convertor remains).
|---> top port to lines eventually terminating at manifold vacuum tree
|---> center port to heat valve
|---> bottom port to solenoid valves that control EGR (EGRC/EGRV I think)
|
|
this is how I have it now:
|---> top port to manifold vacuum tree
|---> Center port to heat valve
|---> bottom port plugged
|
|
Hope this helps 'til I can get a picture!
Just to be clear, this truck has been converted from feedback carb./TFI ign. to std carb./DS II ign. and the computer and all computer controlled emissions equipment were removed (only the cat. convertor remains).
Last edited by whisler; Feb 8, 2012 at 11:39 AM. Reason: Clarity
Thread Starter
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Laughing Gas
Joined: Aug 2010
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From: Northern Kentucky
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From: Denver Metro Area, CO
Did you later delete the picture or sumthin'? I don't see anything....
I see your picture appears to be coming from one of your albums or galleries; are said albums or galleries set up to allow others to see into them?
I see your picture appears to be coming from one of your albums or galleries; are said albums or galleries set up to allow others to see into them?
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Moderator
Joined: Jan 2001
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From: Virginia
If you really want to make it work and simplfy things, go buy a yellow valve for a 79 monte carlo with a 305. It will only have two ports, will release the valve at 100 degrees, and everything will work(if the threads are the same where it threads into the water jacket.
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Laughing Gas
Joined: Aug 2010
Posts: 983
Likes: 49
From: Northern Kentucky
Chris: I don't understand, the picture is showing on my computer screen. The picture is from my album, but was not public. Should that make a difference in whether it shows up for you or not?
Franklin2: I'll try just unplugging the unused port. If that doesn't work I will just go get the Monte Carlo part to try. Thanks for the tip
Franklin2: I'll try just unplugging the unused port. If that doesn't work I will just go get the Monte Carlo part to try. Thanks for the tip
Moderator
Joined: Nov 2007
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From: Denver Metro Area, CO
Yes, it will make a difference; if it's not public, that means it's private, which means only you and people you have set up as a Contact (added to your address book, as such) can see it.
Moderator
Joined: Jan 2001
Posts: 56,989
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From: Virginia
I am suspcious of those yellow lines in the diagram. Are they some sort of venting system? They are hooked to the hot air choke system. Is that port on the back of the carb that the yellow lines go to, the port that runs up into the center of the airfilter? If so, those are not "vacuum" lines.
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Laughing Gas
Joined: Aug 2010
Posts: 983
Likes: 49
From: Northern Kentucky
Franklin2: At least the yellow line that goes to the heat valve is a vacuum line or it would not close the heat riser valve. I know it is hooked up like it was originally. I had that "air choke tube" thing figured out once a while back but promptly forgot it. Let me think about it for a while and maybe I'll remember.