why would using a snatch block help with the heat problem? the issue wan talks about in their response is heat dissipation, not generation. metal transfers the heat to where there is cooler air and offers plentiful surface area for the heat to dissipate. nylon rope on the other hand not only doesn't conduct heat well, it will actually keep the heat in. so by using that nylon rope, you are probably "taking years off the life" of your winch motor. the air ventilation for that motor is already poor enough as it is.
for you computer geeks out there and folks that need another visualization, this is one of the reason why all screws on a computer's motherboard, hard drive and such not are made of a conductive metal. it helps transfer the heat away from the item that might not otherwise have a way to do so. this is especially critical for hard drives (unless you have fans blowing across them, which is a different story).