Loud "PING" in engine...cant be good!

--SORRY ITS KINDA LONG BUT I NEED TO FIX THIS ASAP!!!!!--
I have a 1967 SS Camaro i just bought fully restored. It has a 350 (older block) boared over 40 with a big cam, 650cfm 4 barrel holly carburator with manual choke, aluminum heads pushing about 375 hp with a 4speed muncie rock crusher transmission (manual). I havent had a chance to have a mechanic do a run through of the engine to make sure everything was in order but the other day i was driving it around very leisurly when i heard a puffing noise in the engine well. It didnt puff in idle but only when i stepped on the gas a little. It sounded like an exhaust problem but i wasnt sure. I went home and turned it off and checked out the engine. AS SOON AS i started the engine back up it began to "PING" very loudly and sounded as if something was hitting up against the valve covers. That type of noise. The pinging isnt on every revolution of the engine but rather every 2 or 3. I think I could have bent a rod or messed up a valve or something because the noise is definately coming from the left side of the engine (when in the drivers seat) and sounds as frequent as when the valves open and close. I am not an engine guru and was hoping someone might have an idea of what my problem is. If it helps, i think my carburator has been running really really rich. If i rev up then engine too high (about 5,000 rpm but i dont know i dont have a tach yet) it will flood the engine and die. It makes this noise in idle or when stepping on the gas. If anyone has an idea of what it could be i would appreciate the help.

waht octane gas are you using?

timing is probably off too.

i am using 93 octane. The engine takes a second to start up. It dosent turn over very easily but i have to give it gas and try it 2 or 3 times. It has been like this since i got it. It has about 20,000 miles on it since it was rebuilt.

Since you're using 93 my guess goes towards timing too

I found the problem yesterday but i cannot completely fix it. I took off the valve covers and noticed the rocker arm for one of the cyclanders was completely loose. I could just flick it and it would spin on its bolt. So i tightened it down and then everything was fine. So i went around the block to test it out for about 10 miniutes then it started clicking mildly then the loud ping again. Somehow the bolt holding down the arm is loosening itself!@%!$ in only 10 minutes!

not trying to insult your intelligence, but are you torquing the nuts to the proper torque? also, im not big on building engines, but shouldnt there some form of thread lock on those?

some rocker nuts have a nylon band inside the nut that keeps it tight, yours might be worn out or not there etc. i'd clean the stud and the nut with carb cleaner then put some thread lock on em. let it seat for a good 20 minutes before you start it back up and see if that fixes it. it's not a good idea to drive very long if you hear that noise again, the push rod can get chipped, or worse get wedged sideways between the top of the lifter and the rocker and bend the push rod.

try adjusting your valve lash as well. Also check your timing