noise in my engine
 

ok title sounds stupid but its true
i hear a rattling sound like a bad valve or something i opened the hood and gave it just a little gas and the noise came from the heads mainly the valve cover. first let me say this the sound is at its worst when the car has a cold engine and is turned on or when the engine has been off for a while then on again when its idling the sound is close to impossible to hear when you rev it up to lets say 1500 or more rpms you can hear it. if anyone can tell me what they think it is i would apprediate it also how to fix it lets say it is the valves where can i buy a valve set with lifters and all the other good stuff and should i doi it myself or take it to a shop heres the info on my car
1995 honda accord ex wagon. engine is f22 with 123000 original miles as i can see the only thing wrong with it now is a small oil leak from the motor oil pan. its the oil pan gasket. i just replaced the timing belt water pump and some metal tube that connects to some other stuff i dont know what it is but that was the original problem with the car when it was overheating so i changed everything out anyways the car only overheated a maximum of 5 times in a one week period then i got it fixed. so theres all the info on my car plz help me figure this out

The sound might be the valves, but you don't "buy a valve set". The lifters are adjustable. You would've had the valve cover off when you changed the timing belt. Each tappet/rocker has an adjustment. Look over in the DIY section for a thread about links to manuals. Valve adjustment should be done periodically, I don't remember the interval.