When bedding in a new port ring, be sure to drill all holes, goop up the deck and the port with sealant, install the port loosely with only two screws opposite each other ON the highpoint of the deck curvature (if any), let the goop setup at least overnight, then apply the rest of the screws with light to moderate tightness - plastic screws are much better for this application too (though I used stainless in the picture below). The key to a good tight port seal is to not distort the port base by cranking it to a curved deck. Let the sealant do the work of making up any difference between the curve of the deck and the port. Now your port threads and o-ring will be nicely aligned and mostly jam free.