Engine knock on 1990 Mercury Cougar

Had accelerator stick open for 3 seconds with no load Now have engine knock when accelerating Will still run with power and does get louder as engine warms up. 1969 Cougar Convertable with 390CI

Asked by for the 1990 Mercury Cougar
sounds like you spun a bearing. if you do nothing, it will destry the crank and possibly more.

Thanks Roy, Will have local mechanic check ASAP. Is this a major overhaul and super expensive??