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Comments and advice welcome...frequent reader...rare that I post or comment... I have a 1941 P12 engine and transmission in a 1936 Dodge d2 Touring Sedan. Rebuilt in 1988 with 0.020 overbore. Just changed the water pump and all hoses, new 160 thermo, new radiator cap (original style from Bernbaums), and tune up. During the water pump change, I did not pull the Welsh plugs...I did have the radiator hot tanked. I also flushed, in every direction possible, the engine block and the heater core. I used a garden hose with about 60psi from a 3/4" feed line and used soapy water. The water tube in the block looked to be in excellent condition and I was easily able to run a smaller hose at least 18" into the tube. There was virtually no sludge and the water was quickly running clear enough that it looked like you could drink it. I then flushed in the reverse direction from the water pump opening in the block. I did this twice in each direction...again, the water was clear and coming out with great force...virtually no sludge. After completing the reinstalls, I drove the car for over 120 miles in stop and go traffic (East TN in August...90+ with unbelievable humidity) over the next three days. The car barely got over 180 on a reliable mechanical gauge. The car even idled in the sun for at least 30 minutes without a hiccup. All of this occurred while running without the hood on. Speeds ranged from 30 mph in city driving to 55 mph for a13 mile stretch of hilly highway. The longest continuous trip without shutting the engine off was easily over 1 hour. After returning home and cooling down each time, I verified the coolant level (although I did forget and put in a 50/50 mix) to let the car get in its happy place. I then put the hood back on to drive the car to a show. My trip was to be a total of 70 miles one way with the middle 20 miles on the interstate (55-60 mph). Most of the trip is hilly with speeds in the 45mph continuous range and under moderate to fairly heavy load. The first 30 miles was trouble free, though the gauge climbed to 190+ on the steepest hills. I stopped to fill the fuel tank just before getting on the interstate (17.9 mpg, by the way). While sitting at the station, I noticed that the gauge eased up to almost 205. I then got on the interstate...max speed for any duration was under 60, with most at a continuous 55. Within 7 miles, the gauge was at 225. I stopped to eat a bite and let her cool off. She spit out about 2 cups of antifreeze. Starting back, she was under 180 on the gauge. Within 5 miles, she was back over 225. Stopped again...cooled again...then made it off the interstate onto 35 mph city roads. She just kept getting hotter and hotter. When I heard her hiss, I pulled into a parking lot...she boiled almost 3 gallons out the overflow tube. I sat for an hour to let her cool enough to touch the head and water neck before refilling. This time, I filled her at 70/30. Within 5 miles, she overheated again...pegged the gauge...and spit up her hissy when I stopped at the show. I will digress and wait for your help...and it will be appreciated. Mike