i have felt you pain on washing a semi. a buddy of mine has a peterbuilt that he brings by the house every once in a while, and we put a shinin' on her. it takes a while, but once it is clean it looks niiice. as far as engine specs, he had the oil changed and then had it dyno'd and i want to say that it makes somewhere in the neighborhood of 510 hp on cruise control and a little over 2300 ft-lbs of torque. i guess that it does not make peak horsepower while going through the gears, and the only way to reach it is to use the cruise control.
One of my friends just picked up a new Peterbilt long nose conventional with a 600 hp Caterpillar and an 18 speed transmission. The thing cost $132,000.00 and has a 255" wheelbase. Huge 24.5" polished aluminum wheels and so many other things I can't recall. Oh yes, it has a gps, fridge, microwave and a satellite tv in the sleeper compartment.
I took a short test ride in it since I have a CDL. Boy that thing sure does sound good with a deep diesel clatter and well over 2,000 lb. ft. of torque.