72 - I had similar problems with expanders last spring. Filed all rings to spec & installed first piston. Went in kind of tight. 2nd piston would catch the oil rings and ended up scratching the bore. Figured out that the mfg had put the wrong expanders in the package. Used a correct set of expanders from another box (same part#) and everything went together like butter. Used the an adjustable compressor (solid style) from Speedway Motors. Worked awesome on my 4.375 bore 451.