[Soleman20]

I have a 1994 G20t and the engine rattels/knocks when I start it. It only lasts for 2 seconds and it does not do it on the 1st start of the day, only after it has been started once and sits for 3-4 hrs. If the car sits for 30 min. or an hour, it will not do it. I am positive it is a noise internally in the engine. I asked a mechanic and he said it is not a problem because it only lasts a second or 2. He also said that the lifters are not adjustable on a G20 so its not that. He said he puts a teflon additive in Mazdas that have a knocking problem and it goes away immediately. I am thinking it is the valves, or the cams, or the timing chain/gears. Anyone have any clues or is familiar with this problem?