I have a 69 lemans with a 350 engine and a/t. My family has owned this car since new so I know its orginal engine and transmission. When I start the car everything is good. After the car warms up it develops a clatter. I have been told it sounds like a heat riser clattering in the exhaust manifold. This car Does Not have a heat riser. I have been told the fan is hitting the fan shroud. No. Took shroud off and noise still there. I have been told check the flywheel. I have checked all the flywheel bolts and does not appear to have any cracks. Usually I hear the noise when starting off from a red light or stop sign. On occasions the noise does occur at idle...... Noise happens when the car is in drive or in park. I have went by some of my local mechanics and they also are at a loss to what my noise is. Anyone have any ideas???????