I had my truck running today, it's got a 400 with a 650 manual choke holley in it. I started to notice this really loud popping/clicking kind of noise coming from the engine. At first i thought it was an exhaust leak, then i noticed it was coming right from the air cleaner.

I took the air cleaner off, and it was coming right from the the primaries. I put my hand over them, and the noise got quieter, i didnt feel any pressure on my hand when it happened, so it's not a backfire. The engine is running great though, aside from the noise. It's actually a pretty damn loud noise.

I tried putting my hand all over the engine, seeing if i can feel where it's coming from, the only place i can feel a small "thump" in sync with the noise is the front fuel bowl on the carb. I looked right down into the carb, and opened the throttle up, i didnt really see anything unusual going on in there. Any ideas whats going on here?