Can Not Figure This Steering Issue Out

[AintQik]

This makes no sense and I am at my wits end. Looking for further troubleshooting advice.

67 Camaro, L&H spindles and arms, AGR quick box, stock-type Saginaw pump, March serpentine pulleys.

I've been through 2 boxes, 2 sets of lines and 3 pumps. After 10 minutes of driving the pump starts making noise and eventually fails. Unless I keep getting new bad parts I can't for the life of me figure out what the hell is going on. It seems to be a blockage/pressure issue. The first time I bolted it up the box was leaking out the shaft. I just figured I had a bad box so I replaced it. Second box had no leaks but after a bit of driving (15 mins in the driveway) the high pressure hose blew off the pump and caught the car on fire. Lucklily no real damage. I was running AN lines with plenty of volume and I figured I just assembled the hose poorly. I've never had a hose fail on me in 30 years, but hey I guess it could happen. I replaced the lines with factory lines and all seemed well as I bled the system. No noise, no whine, no nothing. Got the car down on the road and drove to my friend's house, 15 mins away. Pump failed. First there was slight groaning, then heavy groaning, then chunky steering, then nothing. I could get it to have some power intermittent, but it was mostly gone.

Changed the pump and the exact same issue. On stands the car works flawlessly. Got it on the ground and within 15 minutes its toast.

Got a new pump, all have been box store off the shelf things, and started to trouble shoot as obviously there is an issue. At idle the temp goes from 80 ambient to 140. All the air is out. I don't know much about what the temp should be, but from what I can gather so far that may be a little high. I have the pump, 2 lines and the box. No cooler or anything funky.



No noise, no issues. Put the car on the pavement and I can hear the slightest grunt when asked to work. Nothing too crazy. Then it gets a bit chunky. Drove up and down the driveway and checked temp. It was a little over 200. I have no pressure gauge, just using temp to possibly lead me to a blockage conclusion. Still no failure, but it is definitely not right.

Went for a 10 minute ride and gto everything hot. More noise and by the time I got to the house I was getting intermittent failure. Like I turn it and it screams and there is no power. Temp is 210. Valvoline fluid.

No idea what to do next. Don't really feel like building an elaborate pressure gauge but of course I need to get this fixed. Looked at pulley sizes and they seem to be correct. Was thinking it is heat related, but the lines are wrapped in heat protection and I mean 220 doesn't seem hot emough to cause a complete failure in the pump. Measuring temps in the resevour.

Was thinking of taking the return line off and using my hand pump to draw fluid through the system. From what I understand about the box, this would work. Maybe I can "feel" some resistance. I doubt it.

Was thinking of running some tranny fluid in it to see if that has any effect.

I guess you can imagine I don't want to buy another $350 box or pump. I was also thinking of finding a stock box somewhere and just trying that. Unfortunately I only have these fancy ones. I find it hard to believe that 2 boxes were bad out of the box, but I guess anything is possible. However, I think the chances of a blockage in the box is almost slim to none. But again, who knows. Maybe I'm just getting crappy pumps? But, 3 in a row? Something is not right and I'm too stupid to figure it out.

Any ideas? If you told me to sacrifice a jelly covered doughnut on the next full moon while wearing my wife's thong I would do it at this point.