Originally Posted By: KrisZ
I'm not sure what kind of engine designer would select two materials that would tighten the clearance when cold and cut off the oil supply.
The kind of engine designer that wants to take advantage of the weight-saving and heat transfer properties of Aluminum. It's part of the design process to calculate the clearance expected at the lowest expected temperature to make sure there is still running clearance. (Although I have read of some race engines that are built with such tight bearing clearances, they must be preheated before starting or they won't even turn.) But life was slightly simpler when blocks and cranks were both iron-based.
Pistons are always subject to differential thermal expansion issues because they run so much hotter than the bores.
I'm not sure what kind of engine designer would select two materials that would tighten the clearance when cold and cut off the oil supply.
The kind of engine designer that wants to take advantage of the weight-saving and heat transfer properties of Aluminum. It's part of the design process to calculate the clearance expected at the lowest expected temperature to make sure there is still running clearance. (Although I have read of some race engines that are built with such tight bearing clearances, they must be preheated before starting or they won't even turn.) But life was slightly simpler when blocks and cranks were both iron-based.
Pistons are always subject to differential thermal expansion issues because they run so much hotter than the bores.