The upper hose coming out of the water pump is the outlet, and the lower on eis the return. Does it matter which of these you put the valve on?

Sam

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Are you putting in a manual heater shutoff valve, or a heater control valve?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

It is already installed, and works pretty well, but I just wondered if this was the best way to do it. It is basically a manual valve controlled by a cable. This valve is on the return hose. But I have considered swapping the hoses at the water pump to make the engine compartment a little neater. I won;t do it if there is a good reason to leave the valve on the outlet/return side.

I suppose I should look at the diagram supplied with the Classic Auto Air instructions to see if they care which way the water flows through the heater core.
Sam

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I like to put valves like that on the inlet side of the heater core, rather than the outlet side.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I was hoping that was what you would say.

Sam

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Actually the hose on the cylinder head is the heater supply, and the hose on the water pump is the return.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

I have the same Classic Air valve and had it installed in the supply (from head) line and it worked great. Now this was with the factory Slant (stock). After I installed the new motor, which was bottom Hard Blocked, the valve would not hold the water pressure back.
Basicly, with the A/C running and cooling great, if you nail it and bring the RPMs up passed 3000 rpm the A/C would start blasting hot air. I even pinched the hose off with a hose pinching clamp and it still would blow hot at high RPMs. I disconnected the hose and capped it off. Now no more hot air over powering the A/C. Unfortantly the capped port on the head blew open. The cap didn't come off, it ripped through the cap. Finally I looped a hose and no problems. Luckly I live in Florida and not much heat needed.
You may not have this problem as I think the Hard Blocking has caused my water pump to pump at a higher pressure.

I thought I had a picture of the water pump cavity, but can't seem to find it.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Thanks for staightening me out Charlie. Of course that makes sense. I just didn't dig down deep enough to see what was what. But according to my FSM the upper hose is the supply. It works pretty well with the valve on the return, but I guess the thinking is that you will get less heat with it cut off, if the valve is on the supply. I'll have to take a closer look. Since you knew this much, do you also know what size hoses were on the stock set up?

Sam

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The early "A" bodies (the ones I have) use 5/8 hose on inlet and outlet. At some later date (don't know off hand) they went to one 5/8 and one 3/4.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

No 3/4" heater hoses. Starting in '70, the A-bodies got a 1/2" supply (coming off the cylinder head) and a 5/8" return (connecting to the water pump). Up to '69, both hoses were 5/8".

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Thanks, Dan. I was thinking about that. I knew the hoses went to two different sizes, and 3/4 seemed kind of large, but couldn't find the info.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

I put a '70-'72 heater core in my '65 when I installed the factory A/C system. It worked, just like the previous 5/8" + 5/8" core had worked. I think the idea was to prevent water flow noises that could under some conditions come from the heater core with equal-sized pipes, but I never experienced any such a noise. *shrug*

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Any idea where to find the correct 1/2" valve for a 71 with AC? I ordered one but it was a 5/8" valve for a later model that they are now listing for the older cars as well, so I sent it back.

I just put in a new core and now wonder if I should have gone with the older 5/8" x 5/8" core.

I can't say heater core noise has ever been an issue for me. I suppose you could use the 5/8" core and put a 1/2" restrictor in the 5/8" hose if it was. The only thing I can ever hear is the blower.

Those valves have been very tough to get for a long time now. If you can find one with dual 5/8" fittings, buy it and adapt your hoses.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

That seems to be where I am at with this. There are plenty of 5/8" valves, especially if you start looking in the GM bins.

Really it will only take an adapter on the core side, I can change the hose barb on the engine to 5/8" easy enough. I was just hoping to get the right one if possible.

Thanks for the input.