On our 70 Challenger, I have found and investigated throughly a problem where the interior of the car becomes unreasonable hot in the summertime.

I have determined several reasons for this.

1. Engineering of ventilation system could have been better designed. Engine heat(512 ci, TTI headers) can leak past the flimsy rubber gasket that is supposed to prevent engine heat entering fresh air vents. When you open them, just heats further the interior. I have replaced gasket and yes it is installed correctly,,,I have seen many in backwards.

The source for the fresh air is directly behind this gasket, so engine heat that gets past gasket, jus goes into car cabin.

2. Heater control is not a hot water valve that you can control. It merely shuts off air flow over heater core. This leaves a heater core full of 190 degree coolant sitting in your cabin,,,just as an old radiant coal fired pot belly stove. Yes my heater gaskets are fine and heater control cable is properly adjusted.

3. I have decided a half/[censored] fix would be to stop coolant flow to heater in summertime. For esthetics I do not want a shut off valve.

4. Have decided best approach would be to plug the hoses.

Questions. Which hose or perhaps both? How to plug and yet reconnect so all looks normal?

Am thinking of proper sized(5/8 and 3/4) intake manifold plugs that have Allen wrench capability. Screwing these in and removing when our mild winters are near.

Anyone see any problems with this,,,or perhaps a better way to plug the hoses. Do both hoses,,or which one?

Currently driving back from Goodguys on a hot August day is a miserable experience. Am hoping this will help.

Why not taking off all of it including the heater core.. I assume you
only use the car in the summer months.. this would take off weight

Califonua, the government so far permits us drive year round,,,subject to change of course for our old muscle cars. 👌. Good thought however.

All depends how much work you're willing to do. If it was me I'd just remove both hoses during the summer and put plugs in the water pump manifold and then rubber caps over the hoses at the firewall. This is a quick job IF everything is nice and new with anti-seize on the threads. It can be an all day job if everything is corroded. However, if everything is corroded then it is probably a good idea to go ahead and pull it all apart and replace/repair parts as needed. Put a good coat of anti-seize or ARP thread lube on everything and next summer it will come apart quicker.

I never noticed that problem in the '70 Barracuda I had in Calif, but that was just a stock/original318 car.
If you ant it all to look stock, how about modifying the heater core inlet so you can run a heater hose through the firewall, to a hidden valve, then to the core?
May be too much surgery to the box to accomodate all that.
Maybe take a look at a fuel shutoff valve and adapt it to a hose if stock appearance isn't desired; they're less clunky-looking.
Or use a short length of that black foam pipe insulation to disguise a valve.

Or he could just push a piece of solid stock in the end of the hoses and push
the hoses back on.. I would make the 2 pieces so I could pull them back
out easily with some grease on them

Wishing to maintain stock appearance..oh yea just noticed not quite there already.

What about a short piece of wood with an eyelet screw (prob not the right term) to make it easier to grab ahold of it to remove it & likely there is a better choice of material other than wood or maybe just the right type of wood & this (wood type) might not be a critical issue,

Your idea will work with some hard wood like maple or oak and a screw..
stay away from pine or other soft woods due to they would swell up
a lot,, just seal the wood

A hardwood it is.

Hardwood with an eyelet would work. Any thoughts on my original ideas to lightly screw in a metal plug with a hex hole,,,,as used on intakes to block unused holes. 5/8 and 3/4.

Doubt would make much difference if to block only one hose, nor which one. They are different sizes. Heater inlet/outlet. Likely could be a very loose fit,,,,as anything would block most coolant.

I've gone through this thought process before myself but I didn't act on it.

Another idea...pull the two nipples out of the water pump housing, weld them shut at the bottom, re-install them and put the hoses back on.
It would work, but takes more time to go from functioning to closed as the nipples need to be swapped for functioning ones.

Another idea...If you can manage to tap and plug the ID of the nipples, from the top, then that would be much easier to work with.
This seems to almost be the idea you were speaking of?
I don't know if you'll find pipe plugs the proper size since the NPT dimension is the OD of the nipple, not the ID.

Maybe regular steel allen set screws could be used instead.
With some anti seize and or maybe teflon pipe dope, maybe they wouldn't get stuck.

Some quality time spent with a caliper and thread dimension chart will tell the tale.
There's not much material to work with inside those nipples so may have to go metric/finer increments to get a good fit.

It seems to me that if you tapped the ID of the nipples, and used regular straight thread fastener (not pipe), it might be
less likely to get stuck in there. The only issue I can think of is, the internal cutting/tapping will slightly weaken the fitting, so
you'd have to use your best judgement on that.

Marbles stuffed in the heater hoses?

Have you thought of using a in line shut off valve like used in the stock air condition cars(1969 Dodge Polara) that have a cable to control them
I have one like those in my stash of spare parts to use in a street car build soon, most parts store should have them in stock or order one, many cars used them
I think the upper rear nipple is the return hose
I would install it in the hose from the front lower nipple

I’ve been on this forum some 5 plus years. Still amazed but not surprised by the outpouring of differing ideas and variety of solutions to technical issues we all must often deal with working on these beautiful old muscle cars. Even at times I have been able throw in my 2 cents worth hoping that I too have helped someone. It is always a pleasure. Thank you all.

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