Popping popcorn in my 98 stratus

I just bought a 1998 dodge stratus with 114,000 miles.
They said it has a small oil leak, refilling once a month, with synthetic oil.
When driving it home there was a knoking sound almost sounding like if you were to put a baseball card in the spoke of your tire on your bike. Or your finger stopping a blade in a fan. Its real loud and constant. Even when it is just ideling, or driving. On my way home it overheated and I had it towed to my house. I took the valve cover off, but do not see anything out of the norm. I am not an expert though. I don't exactly know what I am looking for. Anyone with this similar problem? Do I maybe need to adjust the valves? Where can I get the proper adjustments for the valves?
Ok well gotta go Napolian Dynomite is starting. lol
By the way, they said it was sitting for a couple of months and it was not making that sound when they parked it.
Thanks in advance.

anyone have any ideas?

loss of oil pressure and got no oil to the head or pistons?

Take it back........FAST!!!!!!!!!

Well I cannot take it back. I finally got it back together today, and had it towed to the shop. I had the valve cover off, and didnt notice any obvious problems. I need this damn car, because I cannot continue putting 140 miles plus a day on my baby durango. lol.
I will give an update when I find out the exact problem, incase someone else runs across this.

bad news gentlemen.
Just got word from the shop. Damn it. threw a rod!!!! Right through the block!!!

eww. sounds expensive. Might wanna get a new engine after that one, since the repair might cost you more than what you payed for the car... if the rod bearing going bad was what ultimately caused this, then most likely the "little oil leak" was the origin of this whole problem. so was the noise the aftermath or the precursor to the rod coming apart? The overheating was probably caused by the friction of the rod and the crankshaft or maybe the piston. Either way its bad. Ive never heard this kind of noise reported, if I ever hear it, I know Im in trouble.

Oh yea, is this a 2.4 L or a 2.0? Just guessing it isnt the V6 because im biased.

hey isnt there a 30 day lemon law even for used cars? You should probably take it back to whoever dumped this on you if you can...

Well I am giving it back, it was my wifes uncles car. But about the lemon law, I think that only applies to new cars, im not sure. It sounds like you know quite a bit about your cars huh. Anyways I think im going to buy a honda Civic 95' 130,000 miles for $3900.00. It is in real good condition. I drive 120 miles a day, and i am tired of putting those miles on my Durango. Anyways thanks for your help.

well, civics are usually solid cars, i think it can take you far if you treat it well. I definately recommend getting any car you buy checked out before you sign off on the deal. Vehicle history report and a full mechanic evaluation. A few bucks now will give you peace of mind and could end up saving you a bundle. Also, the civic probably gets better gas mileage. Good luck and let us know how it turns out.