Another concern when trying to run tight operating bore clearance is thermal distortion. An article in one of the lubrication engineering magazines I receive for work discussed engine bore operating clearances. This article was related to engines achieving very low emmissions and good fuel economy. The article stated that operating bore dimenisions change more due to the thermal stress caused by the coolant temperature increasing and reaching operating temperature than that due to the mechanical stress induced on the block from torquing the cylinder heads.
Setting up a 180 degree F coolant loop (with pump)for an engine block when mounted in a shop boring machine would take a little work. Doing so would be a good learning experience. Effort for results? Also, I wonder what the running versus cold tolerances would be as a final result. An engine has to operate during cold starts with sufficent proper cold clearances before reaching good operating clearances.
