[beck]

How big in diamater is the Dodge water inlet nozzel on the inlet/ac bracket?
I am going to make one from scratch. It appears in the photos that the part where the hose slides on is smaller in diamater than the 4bt inlet.

 

[BobS]

They are close enough to be called the same diameter:
Outside diameters of the radiator connections as measured behind the retaining hump and with some minor surface scale.

1990 Dodge: UPPER=1.785" LOWER=2.285"
P30 Cummins: UPPER=1.775" LOWER=2.275"

The P30 was in a Chevy chassis. Upper outlet points straight towards the radiator, lower connection points straight forward and down towards the radiator.

 

[beck]

Thanks BobS.
I'm heading toward the turning stock to see what I've got.

 

[beck]

I made the base plate from a piece of 1/4" x 3" flat stock. I turned the water outlet from a 1 1/2" x 1 1/4" steel threaded pipe reducer. I bored the threads out of the inside, but left a step inside. I put a step down in outside of the tube also so I could get the bolt heads to clear. I have those 2 pieces welded together. I need to add a tab to one corner that is used to locate the alternator. Then I will flatten up the plate on the grinder a bit then it is to the surfacing machine to make sure it is flat and will seal.

More questions!
My stock outlet has 2 water temperature probes. Are these used? Why measure temperature on the inlet to the motor? I would think you want to measure the temp at the outlet of the motor, or in the head.
I see some inlets have water ports. What are these used for?
My real question is do I need to install threaded inserts in the tube for anything. I left enough room that I can put in at least 1. I will have to check for clearance before welding them in. Has to clear the ac, alternator, motor mount, and who knows what else.

 

[BobS]

More questions!
My stock outlet has 2 water temperature probes. Are these used? Why measure temperature on the inlet to the motor? I would think you want to measure the temp at the outlet of the motor, or in the head.
I see some inlets have water ports. What are these used for?
My real question is do I need to install threaded inserts in the tube for anything. I left enough room that I can put in at least 1. I will have to check for clearance before welding them in. Has to clear the ac, alternator, motor mount, and who knows what else.

Normally there was one thermal switch in the lower radiator connection that was calibrated to run the electric fan. The best location for an after market water temperature probe is in one of the threaded ports in the top front of the cylinder head. With some probes you will need to make a spacer adapter from pipe fittings to increase the depth of the cylinder head port. The other opening in the lower radiator connection was used for the return line from the heater core to the suction side of the engine's water pump.

Heater plumbing: The other heater core line was from the top front of the cylinder head ahead of the thermostat. This way your heater operates independently from the thermostat. This gives you heated water to your heater core before the thermostat opens.

 

[beck]

I wondered about the heater return. My motor had this going direct to the top of the radiator. The radiator has a special nozzle just for it. I don't think I am using the P-30 radiator though so I will need to put a port for that in the nozzle. Thanks again BobS.

 

[beck]

My water inlet is now finished. This is one of the items that you are better off buying than building. I saved about $50 by doing it myself. I have about 8 hr labor invested and a lot of headaches. The only thing I think I may have gained is the bracket that I need to mount my GM alternator. I'm sure that would not have been on the Dodge part that I would have modified. There is a boss cast into the "factory" 4bt inlet. There is a small arm that bolts to this boss and then to the bottom of the alternator. I think it would have been much easier to make a bracket that piggy-backs on top of the Dodge water neck to mount this. From what I'm told here on the forum the Dodge water inlets are cast iron, not cast steel. Cast iron is a pain for most to weld. The 4bt inlet is cast aluminum.