ok the thermal expansion of steel and cast iron is about 10.3 x 10^-6 in/indegF and the thermal expansion of aluminum is about 21-24 10^-6 (in/indegF) so when figuring the thermal expansion assuming engine is built at room temp at 70 deg f and most racers run around 180 deg f so 110 degree difference. the cast iron of the block expands about .00103 and aluminum is about double that. so the difference in expansion is about .001 of an inch, also take this with a grain of salt as the growth goes in all unrestricted directions. without some serious thermal modeling and a good sampling of blocks to get real as cast dimensions from, i dont think anyone is going to spend the time to do this on a 50 year old block. with aluminum heads i've seen about .008-.010 thiousandths of thermal growth, this is measureable at your rockers when your lash is no longer as tight as you set it. but again combustion temps vs oil temps.