Switching over to 10W30 will do one of two things.

1.) It will make the noise go away, which means you have a worn rod bearing.

2.) It will make the noise last longer, which means the whole engine has got enough wear on it that the oil pump just can't get the system up to pressure fast enough.

There aren't any hydraulic rockers or anything in the head on that engine, so it's pretty doubtful that the noise would be valvetrain related. If you had a valve way out of adjustment, it would be constant noise.

As for piston slap, a leakdown test along with a compression test will tell you the condition of your bores the best.