The 3Y is a Toyota engine used in the Rocky/Rugger.
Setting up valve timing you need to set the no.1 cylinder on TDC on the compression stroke.
Turn the crank until the piston is at the topmost point of its travel. Determine this by inserting a plastic or wood dowel in the plug hole and watching it travel upward. Be careful that it does not snag.
At TDC the mark(see red arrow on diagram) on the crank sprocket will be at the lowest point(If the sprocket has been removed the set key -see blue arrow- will be at the topmost point)
Turn the camshaft so that the set key is at the topmost point and aligns with the mark on the engine. If the sprocket has not been removed, remove it now.
On the timing chain you will find 2 links that are lighter in color than the others. These 2 links have to be aligned with the marks on the sprockets before refitting the sprockets to the shafts.