I recently cracked my rear dowel area on my S4 Tii. After some time, I realized I had another rear iron in my basement, bought it with a bunch of parts. It doesn’t look used, and the coolant seal grooves are deeper than my lapped iron. The previous owner ported it, and I’m not sure why they didn’t use it, so I’m assuming the port is bad, the only thing I could think of is that the apex seal might ride on a little bit of air. Not sure about the oil seals.




the port looks good, no nicks around the area, the edges are kinda sharp, will need to make that a little smoother

 

Measure the distance from the center hole to the 'hypoteneuse' arc of the port. It shouldn't be more than about 1mm smaller. Moving that line inwards very far can cause the outer oil ring to cross over it, which is disastrous for oil ring life.