funny sound from motor

i have a stock 91 camaro with the 305 auto and i am having a funny sound coming from the motor... it sounds almost like a chain rubbing against metal... it only happens at around 1100 rmp or so... it did it when i got the car so i brought it to a shop and an old man told me it was the timing chain rubbing so he replaced it... (he says)... whatever he did it stopped for a month or two and then started again... i am wondering if it is possible for this to happen