I'm not sure what you mean by "seal the valves" The only seals that would be dealt with in a timing belt replacement would possibly be a water pump seal if the water pump was done too, or maybe an oil seal. If either was bad, the car may leak, but would not likely make any unusual noises.
It's possible that they damaged the "breather box" and what you are hearing is the unmuffled sound of the air intake of the engine, or it could be something different, such as the timing belt tensioner or something else under the hood. Or the box could have failed due to 'old age', since the car does have some miles on it. It hard to say what happened from the description you gave.
Can you describe what the noise sounds like and when it occurs? Is it a tapping noise that speeds up with engine speed, or a load moaning or roaring noise that gets louder the harder you accelerate? Or something else?
FYI, the timing belt DID need to be replaced at that mileage. If it would have failed, you would be looking at a very expensive engine rebuild or replacement.