5969vette

I have had the car for about a month now and after reading many threads about the heat in the cabin and after experiencing it on a nice warm day Saturday. I have decided to install a shutoff valve inline from the manifold intake to the heater core. After further inspection (before buying the shut off valve) I noticed the manifold intake hose goes to the upper heater core fitting and the water pump hose goes to the lower heater core fitting.

According to the manuals this is reversed? Is this true?
I do have a 1981 Corvette motor in the car but I think it is still the same. Maybe a different heater core? The heater works fine even if the hoses are reversed?
Also I thought the hoses were different diameters inside going to the heater core?

I assume it is just a loop. Should I reverse back to the way the manual shows, you know what they say - if its not broke don't mess with it.

Not sure if this can cause damage the way it is - or did the person before me do it for a reason or just mixed them up?

Also if I leave it the way it is will the shut off be on the wrong hose?

After all that it may not matter at all Just checking with the experts
Thanks

REELAV8R

Can't see how it would matter. Water flows through the core in either direction. Only thing I could see it affecting is the stock shut off valve and it's effectiveness if it doesn't work as well at holding the water back in one direction vs the other.
In your case you are just looking to stop the flow so it won't matter. Some put a shut offs on both hoses to keep the hot water from even getting to the heater core. One is pretty effective though.

5969vette

Thanks!
I kind of thought the same thing. But then I started thinking about inlets vs outlets, flow and efficiency - probably just over thinking the situation

Peterbuilt

Can you move the fitting in the manifold to the water pump and the water pump fitting to the manifold?

Alan 71

Hi 5969,
Originally in 69 there were 2 different size heater hoses.
A 3/4" hose ran from the water pump to the upper pipe on the heater core.
A 5/8" hose ran from the intake manifold to the lower pipe on the heater core.
I guess you should check to see what core is presently installed in your car, and the size of the pipes.
Regards,
Alan

5969vette

Both outside diameters appear to be the same. Not sure about interior diameter yet. I am always leary removing the old hoses from the core fittings since they can be difficult to get off. If the interior diameter is the same then I could simply switch the hoses - sounds too easy. If I am able to switch which line would you put the cut off on? I have heard it does and doesn't matter - not sure

Thanks

doorgunner

I have read that the steel nipple at the waterpump has a small I.D. designed to regulate water flow. Also....use a box cutter to carefully remove a stuck hose at the heater box so the fitting on the heater core won't be damaged.

5969vette

Thanks and I will work on it tomorrow - maybe they will both be the same I.D. and I can just switch the hoses at the core. The hose off the intake has a pre-molded 90 deg elbow so I can't switch at manifold and pump.

Also does it matter which hose has the shutoff?

Iceaxe

No, a single shut-off valve in either hose will completely stop all water circulation through the heater core.

REELAV8R

You're asking for trouble messing with the hose ends on the heater core.

If you don't have to don't remove the hose at that point.
That core is fragile and hoses have a way of getting fused onto pipes over time which could require some force to remove them. Cutting them would be the best if it has to be done as doorgunner suggested.

Just cut a hose and insert the valve wherever it's convenient and reachable to actuate the valve.

5969vette

I agree and hate removing those hoses to switch sides. What if I just leave them as is and put in the shut off? The heat seems to be working fine.

ddawson

I use this

On the 3/4 line that runs from the manifold to the heater box.

REELAV8R

That's what I would do, leave it as is and put in the valve.
I went to a home improvement store and used this kind of valve.

https://www.menards.com/main/plumbin...653-c-9425.htm

5969vette

THANKS - I think I will try the less evasive route for now!

Iceaxe

x2

This valve is much smaller than what most use and is easier to hide out of the way. But it does cost about 3 times what the bigger valve costs.

Paul L

Looks familiar.

ddawson

LOL Yep. I have mine close to the firewall so you don't see it as easy though.

I like the fact this it's pretty small.

Peterbuilt

Yes the water just goes in a loop.
You have a non air conditioned car so you do not need molded hoses at the heater core.
The hoses are two different sizes so you can not just switch them at the core.
Also there is a very good chance of the connector at the heater core breaking so leave them alone.
Whoever installed the 81 engine put the hose adapters at the manifold and water pump in the wrong holes.
Yes! One ball valve is enough.

5969vette

Thanks everyone and it was a piece of cake!