3800 Engine noise

[Guest]

I have a 1988 LeSabre with the 3.8 3800 engine in it. Being the car buffs you are, and knowing a lot about Buicks, I'm hoping somebody will be able to help me out. I bought this car 4 years ago with 110,000 miles on it, and it now has 141,000 on it. Since I've had this car, the engine has always made this weird sound. It is not a ticking sound, but more of a metal rattling sound coming from inside of the engine. I have taken off the accessory belt and listened started the engine, and the sound was still very persistant, so I know it is not any of the engine's accessories. The sound appears to be coming from below the intake manifold. It only happens when the engine is hot, never when the engine is cold, and it only happens when you are giving the engine light throttle at around 1000-2500 RPM. at higher RPM's it does not make this sound, and at idle it does not make the sound. anybody have any idea what it is? This car is in excellent condition, but people think it is a junky car because the engine sounds so aweful it almost sounds like somebody takes little pebbles and puts them in a tin pop can and shakes it around. (but much much quieter than that)

[86 2dr.ltd]

Is the heat shield at the fire wall O.K.? Some of the older 3.8's had lower rod bearing problems.