I have recently purchased another 1974 Corvette Coupe, the car is a very original, well documented, 75k mile car that my wife and I desire to keep as original as possible. Living in Georgia I don’t need heat in the new 74, I don’t want coolant circulating through the heater core inside the cabin, a shutoff valve is unacceptable as is just plugging the intake and water pump port because I want to keep the engine compartment original. In order to cease flow through the heater hoses and heater core I tapped the inside of the water pump and intake heater hose fittings then installed a pipe plug inside the fitting. I reinstalled the plugged fittings and heater hoses, now no coolant in the hoses or heater core and no possibility of the heater core leaking in the cabin. This photo is a trial fitting of some fittings I had from another C3. Once satisfied with trial fitting, I tapped the original fittings from the 74, installed the pipe plugs then installed the fittings in the engine. I started the engine, allowing the cooling system to come to full temperature in order to check the fittings for leaks, with no leaks present, the flushed heater hoses were reinstalled. The intake fitting is tapped 1/4 npt and the water pump fitting is tapped 3/8 npt, there is sufficient material present in the fittings to do the job.
This modification is easily reversed if desired though I cannot see me doing so, one of my pet names for a C3 is “toaster oven”. 🔥

 

Good idea, very hidden.
M

 

Nice solution, thanks for sharing. What have you done for protection from corrosion in the dry heater core,, or do you believe that is not any concern?

 

Good idea

 

Was there a reason why you did not use threaded pipe plugs on the intake manifold and water pump?

 

While I do believe this would be an issue I don’t foresee a reversal, the core is 48 years old and likely in need of replacement.

 

As stated above in the text, the desire is to appear stock. My other 74 is a highly modified Corvette in which I installed a temperature gauge in the manifold and an aluminum pipe plug in the Edelbrock aluminum water pump.

 

you might want to fill the heater core with stronger than 50-50 antifreeze mix to preserve it from corrosion. exposure to air can cause it to fail.

 

Yessir, a point well taken. My only counter thought is that I will never undo the modification in my lifetime and if the coolant were to leak it would leak on my carpet. In the future were I to be inclined to modify this Corvette in regards to heat and a/c it would be with a Vintage Air system.
Eddy