Anyone know what this tiny plug is for?

[Yehoshua]

This plug was smaller than the rest of them. I don't know where it goes ... See attachment

[Yehoshua]

Is it possible the newer block castings have this plug and my older 929 casting block does not have it?

[sctrailrider]

It's a water jacket plug it looks like.... you may or may not need it... just look for a hole in your heads & block...