ok so my friend bought his first s13 and the ka has a slight tick at the front of the motor near the top of the valve cover, now i think it could be chain guides. but before me and the mad scientist rip apart the block to replace the piston ring you fried. oh shit off topic
I have a 300+ KA the timing chain got so bad that it sounded more like an grind every 3 seconds at idle and goes away when its reved up. If your tick is the same most likely its the chain. if its faster then that could be something in the valve train.
Take of vc then take of front plate, and clean the tensioners properly. Then put recommended oil in.
Maybe even change to a new chain to make it the sound stop all together.