Transfer Time from Guanazhou Airport to South Railway Station?

We will be arriving Baiyun Airport at 3:20P from Hanoi on a Friday and will take the metro to the South Railway Station for our train that leaves at 6:44P. We will use the metro from the airport to the South Railway Station. Is this enough time, considering we have to clear customs and immigration in the airport, then allow about an hour for the metro to the South Railway Station. Thank you.