650/750 head ...which one is which

H2RICK wrote:

According to what little I know about the setup, it was not an EGR setup but rather a fresh air injection system intended to introduce fresh air into the exhaust stream AFTER the exhaust valve. This arrangement was supposed to promote additional oxidation (combustion) of the unburned hydrocarbons in the exhaust gases as well as turning carbon monoxide (CO) into carbon dioxide (CO2).
You should be able to see the port up inside the exhaust passage between the valve and the outlet from the head.

OK, so it's more like an AIR set-up rather than an EGR.

I learned something new. Thanks!!

And sorry to everyone for the mis-information I stated.

As long as the head is off, you can tap the holes on top for a 10mm threaded plug (loctite it) and then use a "standard" vaslve cover.

Thanks for the great info.

What are the advantages and disadvantages of pluging the holes?

Is it just to be able to use a different valve cover? what is the downfall if any of doing this?

thank you