On the E7, that's exactly the problem. Too much load on too few motors, and they overheated.
The F40's problem wasn't tractive effort, or horsepower, as they ran, and pulled, just fine. They simply didn't look good to me! The concept wasn't bad, as I liked the SDP40Fs, but the sloping nose made it look like someone tried to streamline a box! If you have a square loco, keep it square!
Also, they were HEP-only, and were rushed onto what was then still a steam-only train, so every train needed a steam generator car. The converted E-units that Amtrak sent out looked like a bad kitbash, with their plated-over windows. They would have done better to keep the ex-BN/GN F B-unit cars, appearance-wise.
Which might be an idea for Amtrak. The long-haul trains still have baggage cars, so put an HEP generator in the baggage car. Then, in an emergency, they could use any available freight loco to pull the train, and the passengers wouldn't notice. The NP put water tanks in baggage cars, to supply steam generators in the diesels, so the weight shouldn't be a problem.
