I'm considering installing an in-line water shut off valve in the inlet heater hose of my '67. I won't go into a long discussion as to why, but it involves summer in Fla.,a leaky heater door, etc. Will the installation on the inlet hose affect the pressure/coolant circulation of the outlet hose back to the intake?? Will unsafe presures buld up in the engine side of the inlet hose?What about the effect on the heater core itself, if any?
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Re: C2 heater hose shut off valve OK?
It's not a problem. Remember there was a heater delete option. SB coolant pumps have an internal bypass built into the pump, so when the thermostat is closed coolant will recirculate back through the engine during warmup. Some SHP engines have an external bypass, too, and the heater core circuit is a third bypass on those engines. C-48 was available without restriction, so just the single internal bypass is okay. Just don't rev it to 5000 when it's cold!
Place the shutoff valve in the heater core inlet hose, which begins at the inlet manifold nipple. This is the smaller (5/8") hose, and you can somewhat hide the valve under the right side accessories if you want.
The valve can really go anywhere in the circuit including the core outlet hose up to the expansion tank tee. With heater delete the circuit just connected the expansion tank to the water pump nipple, which is the inlet side of the pump. The rear port of the tee that the heater outlet hose connects to was capped off and the inlet manifold nipple for the core inlet hose was replaced with a plug.
Duke -
Re: C2 heater hose shut off valve OK?
Installing a shutoff valve on your 67 should be no problem. A water shutoff valve was installed on all 67 A/C cars because the design of the system had cool air from the A/C evaporator passing through the heater core to get to the air distribution box. You can see the shutoff valve in the A/C section of the AIM (UPC C60).
The valve used in the 67 A/C system was vacuum actuated, but for your application a simple mechanical valve would probably suffice. You would have to lift the hood to turn the valve on and off, but in Florida that might be something you do only seasonally.Comment
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Re: C2 heater hose shut off valve OK?
I hope I can jump in on this thread because there is something about the heater hose and AC combo that I have been wondering about. I have read other posts where individual have placed shut-off valves in the heater hose system to stop the hot fluid from circulating to the heater core, thereby reducing the amount of heat dumped into the passenger side of the car. In effect, they say that they are "cooling" off the interior of their cars by installing these valves. Two main questions:
1. Is this "cooling" effect by the installation of the valve true?
2. If so, can I accomplish the same thing using my AC contols? Seems to me that the AC shut-off valve should accomplish the same thing. Which of the AC controls inside the car closes that valve? I assume it is the AC switch that you pull out, since that seems to give a thump when engaged (I've assumed the thump is the valve - maybe I'm wrong).
Just been wondering if I could accomplish the same "cooling" effect using the AC shut-off valve? Thanks.Comment
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Re: C2 heater hose shut off valve OK?
Hi Kirk:
Your 67 A/C system was designed with a shutoff valve, so as long as it is operating properly you are all set. There is a vacuum switch mounted on top of the air distribution box behind the glove box. You can access this switch by removing the glovebox assembly as a unit (door and cardboard box). The actual shutoff valve is installed on the engine side of the firewall, in series with one of the heater hoses.
I can't recall which of the A/C controls activates the vacuum switch, but you could probably figure it out by looking at the C60 section in the AIM. The C60 section will also show the location of the shutoff valve.
Often the switch and/or the shutoff valve are not operating properly, so this is something you may want to check. With no vacuum applied to the shutoff valve, the valve is supposed to be OFF and coolant will not flow through the heater. Applying vacuum to valve opens it.
The source of vacuum for the switch is a rubber hose that connects to the fitting on the intake manifold behind the carburetor. That hose goes across the firewall, through the firewall on the driver's side, and then back across the firewall on the inside of the cabin to the switch behind the glove box. The switched vacuum line that connects to the shutoff valve follows a similar path back out.
To test just the valve, disconnect the vacuum hose at the manifold and plug the fitting to prevent a vacuum leak, or, disconnect the vacuum hose from the shutoff valve and plug it. Then turn on your heater. You should have no heat in this condition.
To test the switch and valve together, cold-start your car, turn on your A/C, and check to confirm that the return hose from the heater core does not get hot when the coolant warms up. Then turn on your heater to see if the return hose gets hot and the heater works.Comment
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Re: C2 heater hose shut off valve OK?
Shutting off flow to the heater core will definitely be an advantage in hot weather on virtually any car.
The question is how did GM design the control system. Does the core valve shut off only when A/C is on? What about when you set the system for no heat and no A/C? This would be easy to check by checking for vacuum at the valve signal line under different HVAV settings.
DukeComment
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Re: C2 heater hose shut off valve OK?
Don,
I can assure you that it works. For my 1967 (non-A/C) I took at trip to Home Depot for an on/off ball valve. Just twist the lever for flow or no-flow. A less than $20 modification. The only harm done if you wish to remove it is $10 worth of 5/8" hose. It looks a little tacky but what the heck. The passenger side of the cabin is cooler now.
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Re: C2 heater hose shut off valve OK?
"Does the core valve shut off only when A/C is on?"
Piece of cake answer, Duke... Check the C60 section of the AIM. You should find a 'truth table' for the various vacuum lines (vac/vent) that tells you how things were designed to work.
Typically, you'll find the hot water shut-off valve only engages when the AC is turned ON and set to MAX cooling. Why? The 'feature' of the Four Seasons system was you could blend heat with cool air to achieve your desired outlet air temp. Therefore, when A/C was running in 'normal' mode, they wanted the heater core hot because you 'might' dial a temp setting less than fully cold and need hot air to blend with...
Also, designers always wrestle with default considerations. What's the 'best' way to set a system's default?
If the default is shut-off valve OFF and something breaks causing loss of control, the occupants sweat on a hot day. If the default is shut-off valve ON and there's a system fault, you risk freezing the occupants and losing defrost/defog controls which is a potential life threatening situation!
And, we have the system as it is. On major fault is when you get the car initially cool and make a short stop (get lunch, run into the store, fill-up with gas). When the engine shuts down, vac is lost and the hot water shut-off valve naturally opens.
Then, by natural convection, hot coolant from the block will flow to the relatively cool heater core and when you start back down the road you get hot air falling out.... The solution is to 'teach' yourself the correct driving habits.
After a short stop, turn the A/C on MAX to close the shut-off valve and use the A/C to extract heat from the now-blocked off heater side of the system....Comment
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Re: C2 heater hose shut off valve OK?
Jack,
From my practical knowledge of the system, you are right on. My heater core definitely doesn't turn off when the AC is NOT on. One thing no one has pointed out is that the kickplate vent door cable is moved to the controls on the dash in AC cars and hence is always open when the AC is NOT on. I wonder if the engineers figured that this permanently open vent would draw in outside air when moving thereby helping to dampen the heating effect of the core.? It is only when you pull the knob for AC that the door shuts, thereby creating a closed environment for the AC to cool (of course you would have to manually shut the vent door on the driver's side).
A second point might be that most often your passenger is a women, and we all know nothing ever makes their feet warm!!!!Comment
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there are also boden cable operated heater
valve used on i believe f--d trucks and if you check the catalog pictures at the auto parts you can find one. this is easier than getting out and getting under the hood if wife get cold on a long trip,just pull the cable. been there done that!Comment
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Re: C2 heater hose shut off valve OK?
Kirk -
The function of that valve (part of the Corvette A/C adapter assembly in the side plenum), operated by the Air-Pull-Fan knob/cable, is shown in the Chassis Service Manual; with the knob pushed in, the system operates on outside air (valve closed to the kickpad grille, open to outside air). With the knob pulled all the way out, the valve shuts off outside air and opens to inside air, recirculating through the kickpad grille. Anywhere inbetween, it blends outside and inside air as desired.Comment
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Re: there are also boden cable operated heater
For a boden cable operated water shut off valve, ask the counterman for a watervalve for a 1973 Dodge Power Wagon with 318.
If you want to get "fancy" and use a vacuum operated water shut off valve, order one for a 1990 Dodge truck with 318 and Air Conditioning. You then can hook the vacuum port to the controller on a shark car, and have it look "stock".
GeorgeComment
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Re: C2 AC max cooling
John,
Now I am confused.
"with the knob pushed in, the system operates on outside air (valve closed to the kickpad grille, open to outside air)".
According to owners manual max ac is AIR PULL FAN knob/cable fully in for recirc of inside air.
Also please clarify the position of RH vent grille door for recirc of inside air.
When my AIR COND FAN knob/cable is fully in the grill door is at a 45 deg angle to the grill. Is this the recirc position? I have assumed this is open to outside air but maybe not. Pulling the AIR PULL FAN cable closes the door. Owners manual says pull this knob for cooling under mild temperatures.
Randy
PS great tip on the cigarette lighter (Corvette Enthusiast), next on the to do list for my 66.Comment
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Re: C2 heater hose shut off valve OK?
If memory serves there are TWO vent doors in the RH side plenum of an AC car that work in 'flip-flop' mode. When one door is open the other is closed and vice versa.
When you're on 'recirc' (MAX AC) the forward door to outside cowl is closed and the inside door to the cockpit is open causing make up air for the system to be drawn from the cockpit. In other modes of operation, the inside door is normally closed and the outside door is open which delivers cowl sourced outside air to the re-heat system.
BUT, the effectiveness of the seals on these vac operated vent doors weren't perfect to start with and over time they typically get brittle and crack allowing air to 'leak'. Plus, if you drive REALLY fast, the ram effect from the cowl will 'test' the integrity of the system!
So, without pulling the vents and restoring their seals (a BIG job in terms of access!), you can expect some stray air leak(s). Today's technology is MUCH better in terms of sealing, cum air flow, and cooling efficiency. But, hey, we're talking 'classic' cars and some of this is what we live with as a consequence....Comment
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Whoops! C2 is the topic...not C3... *NM*
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