Engine Noise (Tick)

I have a 1986 4 Runner 22REC with 271,000 miles. I have a ticking noise comming from what appears to be the rear of the engine. The valves are set correctly. The noise started when I tightened down on the valve cover nuts about 6 months ago. The noise does not appear when the engine is cold. The noise is heard a idle. It may be there at high speed but I cannot here it. I have not checked the oil pressure with a gage. I did check for wrist pin slack when I changed the head out due to eroded water jackets. I have heard of the toyota "tick" before. The last time I heard anything like this was on my 85 Toyota truck when the oil was about a quart low due to leaking front seal. Would like to kee the 4 runner running. I get really odd looks when I take the top off.

on my 90 4runne with v6, the tick is the fuel injectors...

I too have a 1990 4runner with the V6 and Auto. It has 220,000KM's on it. I have just started to hear the ticking sound coming from the fuel injectors. It is very faint in my case, but I would like it to stop if possible.
What are possible fixes for this ticking sound? Does the injectors need servicing or cleaning or will a gas additive that cleans injectors help. My truck runs very well and gets decent fuel economy (430 KM in city and 500KM HWY). I have seen many posts in this and other forums that get worse. BTW I love my 4Runner but am on the look out for a 1996. I want the extra power and once I get one, I will imediately add the supercharger.

The tick you are hearing is a lifter tick. It comes from a valve not being adjusted right. It has nothing to do with a valve cover. Check your valves and make sure they are tighted. The sound is not fatal to the car. It can get a little annoying, but the tightening should fix it.