A I R air injection reaction An air pump, usualy sliding vane design, pumps air into the exhaust passages which help complete combustion of the unburned hydrocarbons and CO. They first appeared on chevies in about 1968 and were on some engines up through the beginning of three way catalytic converters. In order to get a three way converter to work the A/F ratio had to be controlled within a very narrow window and the AIR injection didn't fit the control scheme.
Some AIR systems ran tubes into the exhaust port. Some used a small hole in the exhaust port which was fed through an isolated port system in either the exhaust manifold or the intake. Pontiac and possibly other engines used the negative pulses in the exhaust ports to draw in air past reed valves The system you are mentioning cost virtually no horsepower but the belt for the pump was often removed in the name of more power. It was something to be done by the owner to improve performance, although the results were inconclusive.

The heads have the hole that runs straight from the exterior into the exhaust passage and there was a small bump to help mix the air. This hole is straight and usually has a lot of carbon in it. I was going to use older exhaust manifolds and so I plugged the holes. My plan was to use 1/4-20 screws so after getting the 1//4-20 tap I got the drill bit necessary ahd drilled the holes. I thin threaded the holes. The cast iron of the heads had some hard spots and I managed to break off a tap in one hole. I found eight short bolts and threaded themn into the holes, then cut off the bolt heads with a hacksaw. After I ccleaned the holes by drilling I could have also used JB Weld to plug the holes but the little bolts were free and were so low quality that I didn't want to use them anywhere else. You could probably plug them with oak pegs or RTV or many other things.

R.