It depends on cylinder wal finish. Most modern machine shops use diamond hone stones in a Sunnen CK-10 or a similar type machine to fit the pistons, and a low-tension ring requires very little compression pressure to seat it properly against the cylinder wall surface. The surface finish is almost perfectly smooth, and the ring relies on the compression/combustion pressure to seat it against the cylinder wall. A conventional crosshatch cylinder wall finish is far too rough to work with a low-tension ring. The cylinder wall roughness necessary to seat a conventional ring will damage the surface of a low-tension ring, and result in rapid wear, and/or excessive blowby and short ring life. Since the 305 will probably get the newer ring design on a rebuild, he should be sure the surface of the cylinder wall is compatible with the rings it's getting. On the few street engines I build now, I use Hypereutectic pistons, smooth cylinder wall finish, and low-tension rings. On the race engines, I use file-fit Total Seal rings, with the ring end gap matched to the fuel the engine will run. Alcohol burners get a much tighter ring gap than gas engines, because the combustion temperature is lower, and the ring grows less due to heat. The alky engines are mostly for drag racing, and don't run more than a minute or two at a time, also.
Jerry
