Okay so I have a 95 honda civic and I just recently had the timing belt changed and the distributor changed, as soon as I got it out of the shop I noticed the rattling noise. BUT seeing how it took a a week in a half to get the car back I was content. Now the noise is getting louder and makes my car sound like a piece. So I dont think its a heat shield from the cat because that flew off on the highway from being rusty I suppose, but the sound from that stopped afterwards. So the sound mainly happens when the car is underload or when the pedels more than 1/4 of the way down. It kinda sounds like marbles smacking together. But ive been told it could be the heatshield, but as sad as it is I would say it sounds like valve noise but I dont believe it is though because this car has always been very well taken care of with 120,000 miles. Thanks for the help!