Annoying Sound Coming From engine?

[Antmou]

1. Have the header flanges checked for flatness and have them machined if necessary.

2. It's possible the header bolts are a bit too long and they're bottoming out in the heads without pulling the header flanges tightly onto them.

Exactly what I wanted to say. I almost did the same mistake on one bolt and realized it was hitting the manifold. You have to ensure the screw is deep enough in the engine…