I know the old Williams draw a lot of power, I never figured out what the reason was, just knew it wasn't going to work with the command upgrades. I dropped in a Mabuchi 555 into a couple of them, simply because it was a bolt-in fit, and it was a much better motor. Not a Pittman, but easier to fit. The Pittman would have required new mounting holes and drilling out the flywheel for the larger shaft, something that I wasn't keen on doing. The specific 555 motors I was using had an 8,000 RPM top end, which for the 44:1 gearbox ended up being about 43 scale MPH.