Вчера как раз пробовал, не помогло
proxy_connect_timeout 20s;
proxy_send_timeout 1800s;
proxy_read_timeout 1800s;
client_body_timeout 60s;
send_timeout 60s;
keepalive_timeout 0;
Posted at Nginx Forum: http://forum.nginx.org/read.php?21,233728,233747#msg-233747