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Old 09-07-2016, 12:09 AM
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94 SBC TBI Heater Hose Routing

Can anyone help me with routing my heater hoses and core on my 94 Chevy 350 TBI?
It is in my Jeep, so there it no radiator dump.
I have a port coming off of the top of the intake manifold, passenger side, by the distributor. This is currently connected to the core, then goes to the thermostat housing.
It doesn't seem right, and I am having issues.
I would like to know the best way to rout it, or if I even can, without radiator ports.
I have a plug on the top of my water pump, and I believe it is reverse rotation because of other articles I have read.
The engine came out of a 94 van.
I have read that the back top port is needed for bypass when the thermostat is closed, and I want to turn the core on and off with a valve.
I can attach a photo if needed.
Any help would be appreciated.
Thanks

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Old 09-07-2016, 06:22 PM
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The top of the intake is the water out (pressure) side. The thermostat is also a pressure side. The top of the pump should go to the center of the pump which is the water in side. That is where you need to connect the return hose from the heater. Why do you want to shut it off? The heater manifold should have a door that by-passes the heater core when no heat is selected. The heater circuit acts as the by-pass hose.
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Old 09-07-2016, 09:26 PM
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I have a slightly different set-up in my SBC - Jeep but the pressure side heater hose comes off the intake by the thermostat (I would consider similar to your rear intake), and the return side goes into the passenger side of the pump. I am running v-belts so perhaps alternate rotation to your pump. Based on what "Old Tech" said I would connect to the top of the pump.

I don't use a secondary valve to shut off flow to the heater core.
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Old 09-07-2016, 11:50 PM
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Will tyy

Thanks. I thought the guy that installed it missed something. It looks like they are both hooked up to the pressure side.

I know my serpentine belt is reverse rotation, so I wasn't sure about trying the water pump. Maybe it makes no difference.

The reason I want a valve is because on a Jeep. the core still heats up a lot in the dash, even when the flap is closed. I would like to just be able to shut it off completely.

Maybe I should drill some small holes in the thermostat to allow a little bit of circulation when cold.

I would like is to plug the rear one by the distributor, and go from the thermostat housing to the water pump, but again, I was worried about what I had read about it needing to bypass when the thermostat is closed. If this is an issue, then maybe a tee, or thermostat drilling.

Here is what I read about the bypass;

These ports move around on different installations, basically there is only 2 things going on:

1) a hose picks up pump pressurized coolant ahead of the thermostat which obstructs the return of coolant to the radiator when closed. Usually this is either from the rear of the intake manifold on the passenger (right) side. It can also be from the coolant return ports at the front of the intake manifold before the thermostat.

2) a hose returns coolant to the intake side of the pump (low pressure side). This depending on model and year can be a fitting on the pump, or a return to the suction side tank of the radiator, or a tee fitting in the suction hose feeding the pump from the radiator.

The whole point is to provide a coolant bypass when the thermostat is closed to prevent hot-spot boiling usually around the exhaust seats and spark plugs when there is not yet general circulation; to prevent pump cavitation that would occur with a stall condition when there is no circulation from the radiator; and lastly to provide early cabin heat. AC installations usually include a 3 way valve that shuts off circulation through the heater core when the AC is on but provides a route so the normal bypass circulation occurs. The SBC also includes a bypass drilling on the right side from the head into the block and into the pump suction side, this is to balance right to left side flow as the pump favors flowing to the right side of the block a little bit. It is not intended to function as a closed thermostat bypass being too small for that.

Bogie


Quote:
Originally Posted by OldTech View Post
The top of the intake is the water out (pressure) side. The thermostat is also a pressure side. The top of the pump should go to the center of the pump which is the water in side. That is where you need to connect the return hose from the heater. Why do you want to shut it off? The heater manifold should have a door that by-passes the heater core when no heat is selected. The heater circuit acts as the by-pass hose.
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