I got a cable operated heater valve like this: and put it in the inlet line to my 1930's era heater. I didn't notice the flow direction arrow till I was done, and it is backwards: Points toward the engine. The valve needs to be oriented this way so that the cable pull will operate it correctly, but the mfg wants the coolant flowing the opposite direction from how I have it. I took the valve out and blew through it both in the direction of the arrow, and in the opposite direction and it seemed like it was the same both ways when open, and closed both ways when closed. FWIW this is a non-bypass valve so it is really all the way closed when it's closed. So what's the deal? I know they didn't put that arrow on there for their health, but I can't tell any difference, and of course I'd prefer not to have to redo the line if I don't have to.
I can't see any problem mounting it either way. Can't explain the arrow, but that's the same valve used buy many car makers in the 80s. The arrow may be to eliminate assembly line stupid factor. No disrespect to auto workers.
If there's a butterfly valve in there, mounting it in the wrong direction may cause the pressure to blow the butterfly open.
Since you took it out and blew through it why not just replace it with the arrow going in the right direction?
It really doesn't matter which direction it's mounted,Mile eluded to the water pressure pushing the butterfly open would be highly unlikely,I have this valve on the wagon and it is very tight and mine is also mounted backwards. HRP
It looks more like a ball valve inside than a butterfly, and with the cable on it's hard to imagine it getting blown open so I guess I'll give it a try as is. None of the local parts stores had it in stock at the time I needed it, so it was a special order and as a result a PITA to return/exchange. So if I can live with it that's what I'll do.
You'll find the same valve on E-ay that can be bought with the the valve operating either push or pull.
It has a flow arrow to keep it from creeping open under pressure. It should actually be on the outflow side of your heater anyway not on the in side.
I wondered which line it belonged in. If it was in the outflow line the arrow would be pointing the right direction. My thinking was to put it in the inlet to keep the hot water from ever getting near the heater core when no heat was wanted.
The heater core is full once you fill it you stop the water from flowing it is not going to get "hot" water any more in one direction than the other. If you keep it full of water it is less likely to corrode.
I looked into this when setting up the heater in my '40. All of the Ford heater plumbing pictures I can find show the external (visible) control valves on the input to the heater. It's probable some vehicles are plumbed on the outflow, just have not seen or know of any so far. Heater layout and/or core design may have a part in control valve location.
I install aftermarket heat and a/c all day in different vehicles. We always put the valve on the "push side" with the arrow pointing towards the heater and away from the input source. Hope this helps Matt
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