That was the '74-'82 Chev 305-350 motors; here's a UPI report of GM's screw-the-buyer attitude getting them in dutch with the FTC, including “premature wear with camshafts used in about 15 million 305-cubic and 350-cubic inch V-8 engines produced by GM’s Chevrolet division and used in several models since 1974”.
I visited to Dr. Don Stedman’s emissions lab at DU in the early ’90s. At that time he was working on drive-by emissions testing, and one thing that stands out in memory is a funny-lookin' camshaft on the shelf above Dr. Stedman’s desk. When I asked about it, he swivelled in his chair, opened a file drawer, pulled a folder and tossed it in front of me before explaining: in the earlier developmental stages of the drive-by emissions measuring system, his team had sent notices to owners whose cars had registered as extra-dirty: bring your car in and we’ll fix it at no charge. One such car was a ’77 350 Impala wagon that looked like new and had very low miles but very dirty exhaust and barely had enough power to pull into the repair bay. Elderly original owner said as far as he was concerned it ran fine, but he humored them. Valves were barely opening; camshaft barely had lobes. They put in new cam and lifters, car ran great and exhaust got a lot cleaner.