Screw holes over the exhaust ports
 

I was doing my tear down and repainting of everything and for the first time I noticed a tiny little hex screw above each of the exhaust ports right near where the exhaust manifold hooks up to. They run all the way into the port.

What is there purpose?

If I'm not mistaken they are to release the sand after casting. They serve no performance porpose. You can take them out when hot tanking to get the passages cleaner. But make sure they are closed up tight afterwordsyou dont want them leaking.