Mike Mercury

Thanks to the helpful input from the heater core replacement thread; I am now half way through this project on our 1973 (350 - with AC).

The way the existing core was hosed - it looks like hot water is always running through the heater core... is this correct?

I have seen some vacuum-operated-water-valves listed in some parts catalogs - but don't see where it was ever installed on the 1973???

Fevre

Yes hot water flows through it all the time, you can buy a manual cut off valve (few threads out there on it). The vacuum operated ones are for A/C cars and only stops the flow when the a/c is turned on.

Mike Mercury

I have purchased the vacuum operated heater water valve - thinking it was removed from on our 1973 (that has A.C. ) by the previous owner; but none of the diagrams I have for the 1973 shows this valve; that made me think it was for later year C3's - not the 1973 (even with AC).

Does this sound right?

Fevre

I don't have a/c so I am not sure. Should not be too hard to plumb in, just need to 'T' the a/c vacuum switch to hook the valve to. I personally would just get a manual one so it is off all the time, just open every once in a while to allow the heater core to be flushed a little. No vaccum leak or valve failure worries. Adding a valve is something I need to do myself. :bb

Paul Borowski

Mike, I don't believe this started until '76. Remember I took the A/C out of my '75 and it did not have any such water shut off valve. The cars that do will have a very small white vacuum tube going to the shut off valve from the heater controller unit on your console. When I took my '75's console and heater/AC control unit apart, there was no such small white vacuum line. '76 or '77 even the non A/C cars had this "water shut-off valve".

HDFLH67

I believe there was a vacuum shut-off on my '69. An assembly manual for your year should show you everything you need. They are available through eBay at reasonable prices and are invaluable!

Mike Mercury

since I've already purchased the valve; I'm thinking I might go ahead and install it anyways. I do realize a manual valve is more practical; but this is the wifes 1973 - and she will want it to be "automatic" in opeation.

So... the latter year C3's that had the valve, does anyone know where it was mounted - and which of the two heater core hoses it interrupted?

Mike Mercury

got one; and it doesn't show such a valve (or I just can't find it on the page) - either for the AC and non AC 1973 models.

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[Modified by Mike Mercury, 1:26 PM 5/14/2004]

RMS73

The supply hose is 5/8" and the return is 3/4". I believe the standard vacuum valve fits in the 5/8" hose.
Roger

Mike Mercury

UPDATE:

we're about 95% done with the heater core replacement project. Having an air-conditioned C3 really complicates this task.

While I had all the air ducts removed, they got a good scrubbing (inside & out) with a weak solution of Spic&Span. Man-O-Man they were coated with a thin layer of crudy dust. :( All nice and clean now !!!

The wife was complaining about her tach making noise - especially between 1500 and 3000 rpm. I myself had to strain to hear anything sounding amiss, but you know how easily women can be irritated :)
Since the dash was mostly apart anyways, and since I already had a new L82 mechanical tach in the box awaiting a swap out (purchased from EBay 6 months ago)... we did that swap as well.

About all that's left to do is re-install the passenger carpeting, seat, and map pocket panel. Thanks to all the help I have received in the C3 General section :cheers:

BTW, I went ahead and installed that vacuum operated heater water valve I had purchased. I tee'd off the tan vacuum line that is labled "AirConditioning" and ran the added extension to the new valve. In testing i noticed this tan stripped vacuum line actually has vacuum in all wheel positions - INCLUDIING the off position; except for the heat and defrost positions. So the water flow through the heater core will be stopped unless the wheel is moved to heat and/or defrost. Cool ! (I hope so)

We will see this summer if it was worth adding this valve.

redwingvette

73's did not have any valve so if you add one you will have to come up with a way to turn it on and off. The controls for cars that had it have a vacuum switch mounted to the heater switch much like the one on the headlight switch. I put a amnual switch on my that is setup to have a cable open/close it. I thought about hooking a "choke" cable to it but figured I only need it in the early spring and late fall so why bother.

Mike Mercury

correct; and that is exactly what I did:

I guess I could of done it much simpler by adding a manual water shut off valve under the hood, but this is my wifes car and she likes things to work automatically :)

BTW, her car is featured in this months Corvette Fever magazine in the "Readers Rides" section.

.




[Modified by Mike Mercury, 2:43 PM 5/16/2004]

R 73 454

From what I've seen: 68-71 and late 75-82 A/C cars had the valve, where as 72-early75? A/C did not. Also late 75-79 non A/C cars had 'em. Why they stopped a few years???? I'd love to know! :cheers: