H23 IM EGR port functions

[phantomcow2]

I am drilling out the EGR ports to my H23 IM for cleaning. On the top there are six ports, sit directly above the runners and provide access to them, and two are for another purpose. Each of the four ports are clear; I can shine a light through and see the inside of it's respective runner. However I cannot see any function of the two extra ports. What is their purpose?

Lastly, there appears to be another access port welded over on the NON-EGR valve side of the manifold. Is this worth removing? What is it's purpose?

[Granite CB7]

Obviously the main 4, which you have found and opened up, are for 1 of each of the 4 runners. The other 2 you speak of (between runners for cyls 1/2 and 3/4) actually feed the other 4 ports. These should be clear b/c they would/should clog up last. Lastly the 7th port allows you to easily clean out the 4 main ports, it's an access that goes all the way across the manifold.

If I were you, since you are in there, do all 7 of them, do it once and do it right

[phantomcow2]

Right on. I'll drill the last port tomorrow. I am tapping each of the ports 1/2-20 and putting in set screws for easier cleaning in the future. Thanks

[Granite CB7]

No problem, I did all of mine in 1/2-20 too, just b/c the 7th large port was already the right size, so I enlarged the other 6.