Clanking sound from engine

Brief rundown of my stupidity:

I took off the old quadrajet carb on my 83 GMC 1-ton van (350, auto) to replace it with hopefully an easier to use holly 4160. Unfortunately, when I put everything back together and started her up, there was a strange clanking sound coming from the passenger side head. Question: is it possible that I dropped a nut/bolt/something into the carb port on the intake manifold which made its way into the engine to cause the clanking?

I've already pulled off the intake manifold, exhaust manifold on that side, and felt around with a magnet in the spark plug holes to hopefully find the culprit to no avail. At that point I thought that maybe it had worked its way out already, put everything back together, just started it up to hear the same clanking sound. :banghead:

Now i'm wondering, do I have to pull off the head to find out whats going on or is there something else that could be going on here. I'm a college student with limited time/finances so if theres an alternative to pulling the whole thing apart again that'd be great. Any help is appreciated.

  Chernobyl1

a couple other things that could be important...

its an irregular sound (doesn't sound in time with engine)
-does go faster though as engine speed increases

clanging probably isn't the best way to describe the sound either, more like the sound of pebbles thrown on concrete.

thanks

  Chernobyl1