I agree on the heavier weight oil. The other major difference is the 5w oil is for the tighter clearances and roller lifters.
If it is valvetrain noise, the rockers are not easily adjustable, They were built to just be tightened down with a pedestal type fulcrum.
For a reasonable cost oil with ample Zinc and Phosphorous, Look at Kawasaki general purpose engine oil. It is intended for small air cooled engines but is API rated. It comes in straight 30 conventional and a 10w30 semi synthetic. I am very familiar with this oil as I work for Kawasaki but recommend it for it's qualities not ONLY because I work there.Sorry to sound like a commercial, I just believe this is good stuff.