47-55.1 Continued overheating issue

[Chopped53]

Just read through it all. What a puzzler. Since you had a full-size shop fan blowing through the radiator and it still overheated, it seems like a water flow issue rather than an air flow issue. Makes me think its gotta be the water pump, thermostat, or maybe that 90-degree turn in the return hose.

[mr48chev]

The big shop fan blowing at the radiator should duplicate 25/30 mph rolling down the street and that is usually sitting at a light temp rises drop back down to normal cruising temp. We used to stick a shop fan in front of cars or trucks that we were working on the AC in a shop I worked in in Waco that the boss did a lot of ac work and I learned what I know about ac from working with him. My job was usually putting things back together and hooking up the gauges and vacuum pump (vacuum pump was an old fridge compressor with a fitting soldered to the suction side hose). and turning on the vacuum pump while he was at lunch.

This one boggles the mind a bit because it doesn't follow normal "gets hot" things.

By normal I mean things like:
Temp rises noticably when sitting at a light but drops down as soon as you hit 25 or so and never actually rises at road speed unless you are pulling a steep grade on a serously hot day and there no grades that serious around DFW. That is air flow normally.

Gets hot at all speeds and doesn't cool down much if any at highway speed. Quite often not enough radiator. I serously doubt that is the case here. I have seen it on a couple of V8 swaps with stock radiators that couldn't keep up. Odd thing is that my 77 C30 with a 454 and 10 ft bed with hoist doesn't overheat when pulling either of my boats even in 100 degree heat with a 2 row radiator. The radiator in that truck is way under capacity for the engine but it keeps up. The truck has a clutch fan that will suck a cat through the radiator too.

That the truck doesn't seem to be gettng so hot it pukes coolant may be a good thing. It could be that that is is where that engine want to run up around 200 rather than at 183 or so and there isn't a thing wrong. The heat gun rather indicates that the gauge isn't telling stories or lying about the temp as the one in my buddy's roadster did back in 1978 when his gauge was reading 261 degrees and he stood in front of the car with no shirt on and pulled the radiator cap off and it was only running about 170 with a thermometer stuck in the radiator neck. That car had a Walker radiator and the Walker rep was at the show we were at and I helped the rep find the SnapOn man who had his truck in the parking lot so he could buy the thermometer from him. Ron scared the bunch of us when he pulled the cap off that thing though. That might be another test though. The thermometer that is.

[Hcb3200]

Are you sure all the internal passages of the block are clear?

run a water hose on it with the radiator hoses removed. Run it backwards and forwards. Do a high air pressure blow on it see what comes out.

Remove top radiator hose, remove thermostat, run water hose into top of radiator and see how much flow is coming out of the top hose while its running and while its running at high rpm.

[mr48chev]

I'm pretty sure that his block was cleaned to the Nth degree before it was machined.

[Hcb3200]

I am sure it was/ I am thinking more of the lines of something falling in or in a hose and now pushed into block. I actually saw this happen about 20 years ago. There was a wad of something in a radiator hose. No one thought to check the hoses when they reassemble the engine in the car. pump came on and pushed a wad of some fabric type stuff into the engine. Took the guy four weeks to find it. He determined it came from the hose because more of the same material was in the box that had the other hoses in his parts room.
He figured in fell from something above into the box and into the hose.

I figure by running the water test. You determine how much flow is actually occurring. and it eliminates the above if flow and volume is good. Sort of process of elimination testing.

[dsraven]

not sure what your lower rad hose looks like but an actual hose, with a smooth inner surface, still has more friction loss than a steel tube would have. friction loss slows the flow and makes the pump work harder, with a pressure increase, to get a specified amount of fluid through. is it possible for you to have a section of something like exhaust tubing bent up in the shape of your rubber hose? then attach it to the rad and pump witha short section of rubber hose? just thinking the old stock water pump is not able to overcome the restriction of the long rubber hose with the 90 deg bend.
as a firefighter I have experience with water flow through fire hose. friction loss is a part of the calculation in order to get the correct nozzle pressure and water flow at the end of the hose length. each hose length has a friction loss number assigned as per inner diameter of hose and it's length. larger hose has less friction loss than smaller hose, obviously, to achieve the same amount of water flow. also, inside the fire engine body, from the actual fire pump (a centrifugal pump similar to an engine water pump) out to the hose connections on the oitside, the steel lines are said to have such negligable friction loss that they are not calculated into the pump pressure equation. even though there are 90 degree bends etc.
just a couple of thoughts, but possibly the stock water pump is unable to flow enough coolant due to the change from the stock format of hoses and rad. automotive water pumps are less "engineered" compared to a fire rated pump. also, possibly the rad tubes are not as large inner diameter as the old original rad was spec'd at. the rad can be the same size but require a better pump to flow the same amount of fluid through it due to friction loss, if that makes sense. the water pump still needs to draw coolant from the far end of the engine and drive it through the thermostat, hoses and rad, heater and hoses, etc. then, lets talk about air flow restriction, would it be possible to turn those aluminum flat bars on edge and use angle brackets to mount the fansto the crossbars? the fans and the mounts they sit on are also restrictions to air flow and disrupt air currents I would think. air needs to flow past the grill, which contributes to a disruption of air current flow, then past the other items in the way, before it can pass through the rad, which also looks to have fins that are fairly tightly spaced when compared to the stock original rad. laminar flow is what would be best, where air flows straight instead of turbulent.
possibly all these points add up to your overheating issue as well as a new engine that is now high performance compared to a bone stock factory original.