My car has blue anodized pulleys on the crank the tensioner and it looks like its flaking off the alternator, I bought the car used and was gonna buy UD pulleys but I may have them. Does anyone know the dimensions of common UDP kits?
Yup, that's an under driven crank pulley alright. Should have a big water pump pulley and a fairly large (about 3" alternator pulley) as well. Some people don't opt to change the alternator pulley, as it sometimes causes charging issues.
wouldnt underdrive pulleys all be smaller? the water pump pulley is deffinatly anodized blue and looks moderatly big i have a pic of that too. as you can see the guy before me went nuts with a can of ford blue spray paint. everything is blue top to bottom.
The small drive pulley has a mechanical advantage over the large stock one and combined with the larger driven pulleys, spins all of the accesories slower (thus underdriving them), which consumes less horsepower.
Think of it like you did when you were a kid on your mountain bike. Big sprocket meant great top end speed, but you really had to work your legs to get there. Downshift to the smaller sprockets and pedaling got a lot easier, requiring less energy, but your overall rate of speed was reduced. It’s the same principle.