Do you know what this is??

[~The Jester~]

All it does is let the smog pump put some fresh air in those EGR holes in your exhaust ports. Plug that sucker up, and you'll be just fine. Find a bolt that fits in the threads in the middle, and a big azz flat washer to cover the rest of the hole. Little ultra copper on the back of the washer and you're good to go.

Later heads had those on the back of the head, on both side. Then they had a tube connecting the 2 together. We used to leave the tube on, crimp the end going to the smog pump, and then mig weld it shut.