Hi all if anyone can help i have a 89 fox convertible, i bought it off some old couple and been having some fun with it. I had replaced the original alternator with a gen 3 120 amp with stater. After installing i noticed that my rpms were kinda low and it was kinda stuttering. So i took it for a drive thinking all it need was to be driven. After a while i started hearing loud knocking coming from the engine, i thought it was the valves but its a non interfering engine. So my speculation is that its possibly the crankshaft bearings. Please any advise tips or tricks