This is one of those things I paid VERY careful attention to when porting the LIM on my L27. After every slight bit of porting, I would put the LIM back on the engine and feel inside the ports for the edges of the heads to the edges of the LIM, then take it off and do more porting from there.

The ports to close are the coolant ports shown on this L67 manifold. In the case of the L36, they do not have the recessed area over them. Most people use a 1/4" NPT pipe plug that is headless to keep it flush. When I don't have those available, I clean, scuff up and then fill the UIM coolant passages. Does the same thing in the long run. Although the LIM plugs are preferred, then you don't need to drain coolant to remove the UIM.


And ... I gotta find the pics of the u bend hogging.