440 head noise. Perpetual problems. Problem solved

So I went back out and bumped the motor and took a 9/16 and checked the flex plate and I have a super bright light and can see pretty far up in there and it looks great, doesn't seem to be anything wrong with it. So I started it again and again it sounded perfect for about 45 seconds to a minute then it starts rattling very loud and there's also this slight ringing sound kinda like a bell being rung. It's hard to hear because of the 440 beating the ground. I really don't mind working of this thing for as many hours as it takes. There's a rod run here in Cherokee nc this weekend and I was hoping on making all these corvettes, camaros and mustangs look sick but I guess not this time lol