Knock/Ping

I have a 91Toyota Pickup with the 3.0L V6, nice truck. However lately it has started to develop a knock/ping. Sounds like lifters or something, coming from the engine from the best I can tell. Does anybody know of anyway to help remedy this problem, a way that doesnt invole taking the engine apart. I just want to try to stop it where it is, because I don't want to have to pay for it to get fixed, that's a little expensive.

I tried higher octane fuel and some oil additive stuff, niether did anything really :(

What do I do :confused: