I have 1970 Ford truck with a 390 that has about 1000 miles on it. Bored .30 over .I recently replaced head gaskets in it. Truck runs strong except when it get up to temp my oil pressure drops and it starts to tick and make noise I removed both valve covers and listened to it run. Push rods are all tight the rocker shaft is on correct. I've heard that it could be bad cam bearings. Can someone give me some insight.