69 427/390 Heater Hose By-Pass Question for Duke

[Brad H.]

This text is a continuation of my previous heater core question. Background: 69 427/390 with overflow/header coolant tank. I would like to bypass the core using non-standard means. I would like to keep the outward appearance authentic but still by-pass the heater core. I am considering using internal hose plugs pushed up into the hoses just prior to the hoses pushing onto the heater core tubes. This would eliminate coolant flow into and out of the heater core. All the rest of the system is plumbed correctly. Would doing this have any adverse effect on the engine? I realize the heater will be inop which is the reason for this. Bypassing the core by just connecting the hoses is not something I want to do. I will remove the core and get it fixed if that's the only way to go.
Thanks very much,
Brad

[Duke W.]

Re: 69 427/390 Heater Hose By-Pass Question for Duke

If I'm reading your situation correctly, you have a leak in the heater core and are suggesting internally blocking both the heater core inlet and outlet hoses. That should prevent any leakage from the heater core assuming the hoses are completely plugged and will withstand 15+ psi pressure. Before connecting the blocked hoses to the heater core you should flush it thoroughly with water and let it thoroughly dry.

The only potential issue is the coolant bypass. When the thermostat is closed the heater circuit acts as a bypass to allow coolant to circulate. In the case of small blocks this is only one of up to three bypass circuits. All small blocks have an internal bypass - the "third hole" in the water pump legs. In addition, most SHP/FI small blocks have an external bypass which is the short 90 degree hose between the top of the coolant pump and the inlet manifold.

There needs to be at least one bypass. Otherwise, when the thermostat is closed there is no way for coolant to circulate and the coolant pump can cavitate.

I'm not sure of how bypass circuits are configured for big blocks, so perhaps someone who is more familiar with this aspect of big blocks can chime in.

Duke

[Brad H.]

Re: 69 427/390 Heater Hose By-Pass Question for Duke

Thanks Duke!
I suspect the safest course of action is to just repair/replace the core.
Appreciate your expertise on this Forum!
Brad

[Dale C.]

Re: 69 427/390 Heater Hose By-Pass Question for Duke

Brad
Is your car a C60? There are some differences if it is. See page 80 of new JM.
Dale

[Brad H.]

Re: 69 427/390 Heater Hose By-Pass Question for Duke

Dale, it's a non-AC car.
Thanks,
Brad