95 Nissan oil light on

I have a 95 nissan with the 2400 4 cly engine. I got the truck and the guides on the timing chain were shot, I replaced the timing set, replaced the oil pump because of all the crap in the pan. I used carb cleaner in all the oil passages I could get to to clean them out, got everything back together and the truck will start and run fine but the oil light will come and go, no certain rpm or speed just comes and goes, it also has valve clatter even if the oil light is not on. I pulled the rocker assemblies and cleaned everything. All looks good but still get a frequent oil light and valve clatter. I also ran the engine with motor flush twice (its on its 3rd oil change with only 20 miles) Any ideas?