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Where to connect heater core lines *pic*

3K views 16 replies 4 participants last post by  BogiesAnnex1 
#1 ·
I have this intake manifold



I have one line for heater core hooked up to water line.

Are those back to ports on the intake connected to water jackets, if so can I use that for the other line or do I need to use the port up front by the thermostat?
 
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#3 ·
The water pump pushes water through the the block, up through the heads, up into the intake and out the thermostat housing and back into the radiator. The four corner water intakes are all outputs of the system loop. Normally the two in the rear are plumbed to the thermostat housing. You could use any of those four in the intake and plumb to the heater core. The other side of the heater core has to go to the water pump though.
 
#4 ·
This intake is designed for four corner return, the rears are externally connected. On factory intakes this is done under the intake on models beginning in 1986-87 to the end of production. It is designed to prevent the accumulation of steam and gasses over the rear combustion chambers, a long standing problem of anybody's V8 for a long, long time before addressed by the OEMs.

Any of these taps before the thermostat can be used to source the heater as this will provide circulation through the heater core and provide a bypass flow when the thermostat is closed that does not go through the radiator. This provides a faster warm up with early cabin heat and a moderately high coolant flow through the jackets to prevent the formation of hot spots that develop very quickly around exhaust seats and spark plugs when the thermostat is closed.

Any of these taps provide the pressure side for the heater and bypass. The return is from the heater either to a fitting on the top of the coolant pump which is internally connected to the inlet side of the pump. On some models the return hose may connect to the cold side tank (pump inlet) of the radiator and some connect to a tee fitting in the lower hose between radiator and pump. One of the purposes of this return location when the thermostat is open is to introduce hot coolant into the cold incoming stream to moderate its temperature to reduce thermal shock to the forward cylinders and to keep the system operating in a tight temperature range around the thermostat's rated temperature. Kind of a poor mans solution to a difficult problem, when you look at the LT1 and LT4 they use a dual switch thermostat that is controlling the outlet and inlet temps and mixing the two before it enters the engine, this is also common to big trucks and heavy equipment cooling systems, works super well but is a costly solution.

Bogie
 
#14 ·
Typically with this manifold a pair of right angle fittings, 1/2 inch pipe to 1/2 inch or 5/8th hose would connect from the rear taps to another pair of like fittings to the front taps on the coolant return part of the manifold.

To plumb to the heater replace one of the fittings with a tee or put a clamp-able tee hose adapter in one of the hoses and run a line from there to the heater inlet side which will be 1/2 or 5/8ths. The return from the heater core will be 5/8ths if the inlet is 1/2 or it will be 3/4 if the inlet is 5/8ths; that line runs to the pump or cold tank fitting on the radiator or into the inlet hose which ever way this is configured. The key is tapping from the high pressure side which is anywhere behind where the pump bolts to the block to somewhere on the low pressure side which is the pump inlet. The fitting on the top of the Chevy pump leads to the inlet side of the impeller so it is low pressure as is the cold side of the radiator which is where the pump draws from whether a cross-flow or down-flow that connection will near or at the bottom of the radiator. Some returns are also a tee into the lower hose. So which ever you have that's where the return goes.

Into an aluminum manifold I'd recommend aluminum, stainless, or brass fittings, perhaps even plastic, to avoid or at least reduce the corrosion problems that occur with common steel in aluminum.

Bogie
 
#13 ·
No worries.

Racers will often use the rear ports and plumb lines to the thermostat housing to get more water moving through the back of the heads. It's also common to plumb lines from the center of the heads between the exhaust ports to the water pump. Again it's to get more water flowing between the exhaust valves.

In your case you can use one or all of the ports on the intake because they are all on the pressure side of the pump. Your other heater hose will go the suction side of the pump to get the flow through the heater core.
 
#17 ·
It is important to get a flow off the back of the engine. Some is better than none. In that vein you can put a tee in one side and tap the other side to the tee and then from tee to heater core. The return from the heater core back to the inlet side of the pump where ever your configuration places that typically it's the top of the pump.

Or you can plumb one side (passenger most likely) to feed the heater core. Then plug the forward external return into the manifold on that side. Complete the heater/bypass circuit to the top pump fitting or whatever fitting is on the pump intake side of the radiator. On the opposite side (drivers) connect the rear outlet to the front.

Either of these configurations provides a 4 corner return with a bypass circuit that feeds the heater.

Bogie
 
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