Vacuum water valve

ceebuddy

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This is from the 1972-6 MTSC:
Heater_Valve_1.jpg

Heater_Valve_2.jpg


"The water valve used on these models is a combination bypass and flow valve. The flow part of the valve is fully closed by moving the temperature control lever all of the way to the left. This shuts off flow through the heater core. The bypass part of the valve is a spring-loaded poppet. When the flow valve is closed, coolant pressure opens the bypass and coolant returns to the engine without going through the heater core. The pressure-operated bypass valve automatically compensates for changes in engine speed and coolant pressure. This bypass feature results in very good coolant volume and temperature control."
 

Big_John

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This is from the 1972-6 MTSC:
View attachment 261531
View attachment 261532

"The water valve used on these models is a combination bypass and flow valve. The flow part of the valve is fully closed by moving the temperature control lever all of the way to the left. This shuts off flow through the heater core. The bypass part of the valve is a spring-loaded poppet. When the flow valve is closed, coolant pressure opens the bypass and coolant returns to the engine without going through the heater core. The pressure-operated bypass valve automatically compensates for changes in engine speed and coolant pressure. This bypass feature results in very good coolant volume and temperature control."
Interesting, but that is the cable controlled version. Can we verify that the vacuum controlled valve operates the same?

What this does show is that it doesn't mix the water going into the heater though. It bypasses though, which is something the replacement valves don't do.
 

ceebuddy

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Good point, but I do not think it would matter whether it is vacuum or a cable that opens the flow valve. The base of the entire heater valve unit was the same in both cases having four hose nipples.

You are right about it not mixing hot and cold water streams concerning the water flowing to the heater core. However, if you have the temperature lever in a middle position, I assume from the diagrams that this would result in both the flow valve and the bypass valve being somewhat open at the same time.
 

Big_John

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Good point, but I do not think it would matter whether it is vacuum or a cable that opens the flow valve. The base of the entire heater valve unit was the same in both cases having four hose nipples.

You are right about it not mixing hot and cold water streams concerning the water flowing to the heater core. However, if you have the temperature lever in a middle position, I assume from the diagrams that this would result in both the flow valve and the bypass valve being somewhat open at the same time.
I would say that, yes, they probably work the same, but I've been surprised before. LOL

From the diagram, I would say that the bypass, being spring loaded, will vary the amount of water that returns to the engine based on how much flow. More flow to heater, less bypass etc. That would only make sense.

IMHO, the question is if it really makes a difference. I would think that having it bypass would make it easier to control the heat, but is it enough to be noticeable?
 

Big_John

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ayilar

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I bought the Everco H1949 from (a) link sent by @saforwardlook; it arrived promptly and @71Polara383 has already installed it. It bolts right in, following the instructions on the box (posted below, in case this is helpful to someone -- for C-bodies, it is important to re-use the old bracket).

Now that half a year has passed, and after driving close to seven hundred miles in situations when I needed the heat, I can provide some feedback on how well the Everco valve performs. Short story: it does work and does modulate the heat but, as @saforwardlook had mentioned to me, the response is not immediate -- and the modulation is not as good as what I am accustomed to in more modern vehicles. Intermediate levels of heat, in particular, are more difficult to achieve.

Overall, I am reasonably happy with the valve, but I will be interested in hearing from people's experiences re: how the new "factory-look" HCV repro works for 1971's.
 
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Gerald Morris

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....
I found another aftermarket valve on Ebay. Some seem to think the plating on the outside is real gold, so they price them like it is. It took me a while to get one at the price I wanted to pay. In the meantime, I put a ball valve in the heat hose in it's place.

I haven't gotten around to replacing the valve (winter project!). I may leave the ball valve inline just to provide a positive shut-off so my A/C works to full potential.

The very fact that one CAN install a ball valve in place of the OEM vac valve is EXACTLY WHY I LOVE THESE OLD C-BODY MOPARS! RIGHT ON! That's the kind of solution I LOVE! Had a 1959 International Travellall I did shit like that to. Leave the ball valve in forever.
 

Gerald Morris

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I have been thinking that at some time I may convert the vacuum unit to a manual control unit, it wouldn't be too hard as routing a cable can be done discreetly and the lever that actuates the vacuum unit at present could be modified to do a cable so nothing changes in the dash area.

I just rotate the control by hand to set the heater to defrost when I want it to do that. I pulled the vacuum switch 3 yrs ago but kept the valve, sans connection to the intake manifold. I currently use only the ported vacuum for the distributor on my ride. All else has been eliminated.
 

Mr onetwo

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Does anyone have a failed, leaky example of the original heater valve they are willing to donate for an experiment? I would love to take that body to my machinist friend and see if he could reproduce that body in aluminum to make a retofit option. PM me if you do.

s-l1600.jpg
 

saforwardlook

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Does anyone have a failed, leaky example of the original heater valve they are willing to donate for an experiment? I would love to take that body to my machinist friend and see if he could reproduce that body in aluminum to make a retofit option. PM me if you do.

View attachment 333480

I am pretty sure I do have one I can send to you. Please provide me a PM with a mailing address and I will send it to you.
Thanks!
Steve
 

saforwardlook

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I did find my last cracked one in my shop this afternoon. I will get it in the mail to you on Monday.

Thanks for looking into this for us all..............
 

ayilar

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Now that half a year has passed, and after driving close to seven hundred miles in situations when I needed the heat, I can provide some feedback on how well the Everco valve performs. Short story: it does work and does modulate the heat but, as @saforwardlook had mentioned to me, the response is not immediate -- and the modulation is not as good as what I am accustomed to in more modern vehicles. Intermediate levels of heat, in particular, are more difficult to achieve.
Two years later, I confirm those initial impressions, gained with Medina (my T-code ‘71 Monaco) after several more thousand miles with that car, and now after a few hours in cold weather in my 1970 300 U-code ‘vert.

@Mr onetwo — any update on your experiment?
 

Mr onetwo

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to your question ayilar...the body is too complex to machine for a reasonable price.It is packed away for the winter, but I will post up photos of the assembly all taken apart for others reference in the spring.It is a surprisingly complicated piece of engineering.
 
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