smoke comming from my oil cap

I just noticed some smoke comming from my oil filler cap when i removed it with the motor running. not to much but this was at idle. i have replaced the pcv valve, and checked the hoses and they are fine. Im doing an oil change tonight, and I need advise what else I should check.anyone please help.

1981 bronco-351w.

That may be from some carbon build-up or sludge on the rockers and inside the valve covers. As long as the engine isn't overheating, and you don't see blue smoke in the exhaust, I'd say you're O.K. Might try a different SAE-weight oil

thanks, i got a little scared for a minute.