Problems with excessive casting flash occasionally created warranty problems for Buick. Attached are pictures from three dealer service bulletins on '55 models. Overheating problems were created by casting flash in water passages near the pump. Broken and bent fuel pump arms were caused by casting flash in the pump arm opening. Rough idle troubles developed due to flash in the exhaust crossover passages.
Don't have a complete set of service bulletins for '67 yet to see if there were any flash issues. By the mid-'60s, the service bulletins were running about 500 pages/year so there were plenty of other mods, repairs, and upgrades to monitor. Nonetheless the '67 full-size Buicks had a better than average repair record according to Consumer Reports (see attached used car ratings).
What has been, can be again. (Bob Wills, 1942)