I have a 1984 Z-28 camaro with an l69 305 HO. It has and oil gage instead if an idiot light.

When the engine is idling (600-800 rpm), the oil pressure gage reads little if any pressure. If you rev the engine at all by stepping on the gas (over 1200 rpm) , the oil pressure gage reads a healthy level.

Should I be concerned?

What should I check ?

What are the various things that cause this problem ?

 

A good rule of thumb is 10psi of oil pressure for every 1000 rpms. Also the stock gauges in our cars aren't the best.

 

Before you get nervous, temporarily attach a mechanical oil pressure gauge (or even better, permanently) and see what it says.I had really shaky oil pressure readings on my factory gauge a few years ago and turned out it was the sender.
On the mechanical gauge, pressure was fine.
If pressure still goes away at idle, it could be big clearances from wear on bearings.If that's the case, plan on rebuilding or replacing soon.
And like Mark said above, the rule of thumb is:10psi for every 1000 rpm minimum.
-Rich-