1961 Heater Hose Hell

[William H.]

I need help straightening this out. My 1961 was set up using 5/8" hose both top and bottom. The fittings on BOTH water pump and intake are 3/4". So prior installation jammed 5/8 hose over 3/4 fittings with predictable result - hose burst at fitting ridge.

My research says correct installation is 3/4" hose from water pump through firewall to copper elbow (which reduces to 5/8"). Top hose from intake to heater fitting in engine compartment is 5/8". No problem - I buy 5/8 fitting replacement for intake. Now the problem - the 3/4" hose does not fit through the fire wall with rubber grommet. I bought new grommet from Corvette Central - same thing. Ribbed 3/4" hose is also from Cprvette Central.

Its making me crazy. Am I doing something wrong here? Does anyone have a solution (other than run 3/4" hose through firewall and bag the grommet - I worry it may eventually rub and leak)

[Bob H.]

Re: 1961 Heater Hose Hell

Hi

My 62 needed a heater core. When I replaced it, I also replaced the 90 degree elbow and hoses.

As I recall, the 3/4 side of the elbow is what protrudes thru the fire wall with the hose attaching to it on the engine bay side with a hose clamp. Therefore, the hose itself does not go through the firewall.

Maybe someone else will confirm this is correct.

Bob

[William H.]

Re: 1961 Heater Hose Hell

That would be a great answer and would solve my problems. Thanks so much for responding. If a 61 owner could verify this it would be great. In that case the grommet would be a little loose for that copper elbow, but so be it.

[Terry D.]

Re: 1961 Heater Hose Hell

Not at home this weekend so I can't look, but the assembly manual should show that. If you don't have one, now would be a good time to get one. Lots of that kind of info in it.
Terry

[Dominic E.]

Re: 1961 Heater Hose Hell

there is a copper elbow that goes through the firewall 3/4 to 5/8. paragon catalog, page 41.

[William H.]

Re: 1961 Heater Hose Hell

Thank you Terry and Dominic. So I went back and studied the Assembly Manual again at Terry's suggestion. It shows the grommet preceding the clamp at the copper elbow. So I would say that the hose must go through the firewall before the elbow is installed. That unfortunately gets me back to square one. I am now down to three explanations: (1) the 3/4" hose from Corvette Central has too large an exterior diameter; (2) the hole through the firewall is too small; or (3) the grommet itself is the wrong one.

[Bob H.]

Re: 1961 Heater Hose Hell

I see what you are saying about the assembly manual picture. However, it also shows in a couple places where the hose clamps are side by side. I can't imagine only one clamp on the fire wall side (5/8ths) and one inside the car (3/4). Also, postioning/spacing of the elbow off the heater core seems to dictate it's design was to turn and go through the firewall. Hopefully, someone with better knowledge will speak up! Now I'm curious if mine is wrong.

[William H.]

Re: 1961 Heater Hose Hell

I am certainly not the authority here but I typically do thorough research. I am surprised at the diversity of opinions that I have found on various sites relating to this issue. So I thought it would be helpful to provide a summary based on what I believe to be the most reliable sources should anyone in the future refer back to this thread. First the facts:

The 1961 - 1962 NCRS Technical Information Manual (the "gold standard" for anyone using this site) specifies that the hoses are to be 5/8" at the intake manifold and 3/4" at the water pump. It also specifies (and I quote) "There is a rubber grommet outboard side of the car for the heater hose to pass through the firewall."

The Assembly Manual for model year 1961 - 1962 includes a diagram. The diagram shows: (1) the hose from the intake manifold connects to the heater control valve pipe on the engine compartment side (i.e. 5/8"); (2) the hose from the water pump passes through the grommet at the firewall, then clamps to a copper elbow (i.e. 3/4").

Now we are done with the facts and I offer my own color commentary. First, the fact that the elbow appears to be sized to accept 3/4" hose on one end and 5/8" hose on the other end supports the notion that it is designed to accept the 3/4" hose from the water pump (the other end connects the short 5/8" hose from the elbow to the heater).

So there are all sorts of explanations as to why the 3/4" hose on my setup won't fit through the firewall grommet (wrong grommet, aftermarket hose wrong exterior diameter, etc). Since I feel that drilling out the firewall hole to a larger diameter (not to mention the subsequent hunt for a larger grommet) seemed like a very bad idea, my solution was to have to copper elbow go through the firewall. I feel nearly certain that this is incorrect as it is somewhat an awkward fit and is contrary to the diagram in the Assembly Manual but it seemed the least incorrect of the options available to me. It would seem that the elbow would have been made with a longer stem if this were the intent, but I could think of no better solution and did not relish spending the rest of my existence researching heater hoses. Case closed and thank you everyone for being helpful to me here.

[Dennis C.]

Re: 1961 Heater Hose Hell

I had no trouble setting up my '61 heater hoses according to the assembly manual.

The 3/4" hose passes through the outboard firewall penetration containing a grommet. It clamps to the elbow inside the car under the dash. The 5/8" hose connects to the control valve inside the engine compartment. This penetration doesn't receive a grommet, but as a seal - a pies of flat foam.

I bought my hoses from Paragon. Make sure the elbow you use has a ridge for the clamp to rest against to prevent the hose from slipping off. Some vendors sell a copper street el for this elbow and it doesn't have the ridge.

Hope this helps.

Dennis

[Dan D.]

Re: 1961 Heater Hose Hell

I will be fighting this battle very soon with my 57, so I thought I would see if I have the same problem. I do. My hoses are both 5/8, but other than that, 57 is the same setup as 61/62. I also bought new hose and grommet from CC. Results are new hose is not going to pass through the grommet. One thing I am positive on is the hose does pass through the grommet and attaches to the copper ell inside the car. That is the way mine was configured when I took it apart and I am sure that is correct. Measuring things it looks like things are a little too big or a little too small, all in the wrong direction. Measuring rubber is not a precise science, but this is what found.
1. New hose OD is about .03 larger than old hose. Hose ID is perfect at .62 and fits just snug over the ell.
2. New grommet ID is about .05 smaller than the old grommet.

So it does not work. I have the same problem that Bill does. I too do not want to drill out the firewall, and I do want the hose to extend through the firewall as originally intended. I am thinking about how to enlarge the hole in the grommet. Not easy to do with rubber. -Dan-

[Dennis C.]

Re: 1961 Heater Hose Hell

2. New grommet ID is about .05 smaller than the old grommet.

So it does not work. I have the same problem that Bill does. I too do not want to drill out the firewall, and I do want the hose to extend through the firewall as originally intended. I am thinking about how to enlarge the hole in the grommet. Not easy to do with rubber. -Dan-[/quote]

Dan,

I do remember the hose through the grommet being a tight fit, but with a little silicone spray it fit OK.

What does the grommet look like? I am wondering if there are different gromments.

Dennis

[William H.]

Re: 1961 Heater Hose Hell

Dennis - your description is concise, accurate and 100% consistent with both the Assembly Manual and the NCRS Technical Information Manual. I don't know why my 3/4" hose doesn't fit through the fire wall but I suspect that Corvette Central sells fat hose. If I have the opportunity to have the coolant out of the car again, I may try and order the Paragon equivalent. Thank you for taking the time to reply.

Dan - it is not too late for you. You may want to consider checking out the paragon 5/8" if the CC hose isn't fitting. Good luck.

[Dan D.]

Re: 1961 Heater Hose Hell

1. The new CC grommet looks as identical to the original as one can expect. It is split and cut on an angle - like the original. Even the marking is the same. A fancy 'B' within a circle and a 'C' within a circle right next to it. It would appear from this like the same manufacturer in both cases, Hard to imagine for 53 years difference. I'm sure it has been re-tooled several times, which might explain the slight difference in size. Being in the electronics business all my working life I have delt with grommets for 50 some years also. But split, and cut on an angle is something I have not seen before. Most grommets are not cut.

2. Yes, I agree. If I can't make this work I may just re-order from Paragon. Not talking a lot of money here - and aggravation is worth at least something.
-Dan-

[Dennis C.]

Re: 1961 Heater Hose Hell

I measured the OD of my 3/4" hose at 1.048".

Regards,

Dennis

[John F.]

Re: 1961 Heater Hose Hell

If you are trying to ream out the grommet, I would try placing the grommet in the freezer to get it harder and then with a round coarse file ream it out to size.

John F