Oil won, t lubricate the camshaft, I did change.

You need to check the oil line for clogging. Are you getting oil pressure at the oil pressure switch?
Was anything done prior to this occurring?

One or more of the valleys maybe plugged on top of the engine. You may have to take your valve cover off and do some cleaning or remove the head and have it disassembled. Its plugged somewhere leading from the pump, or the pump isnt putting out the proper pressure required to lubricate the whole engine ( which with the carbed mazdas this really should be a issue since about a quart and a half always manages to collect on the top which my 87 did ) ( hence the smoking at start up )