I would imagine that even though you have changed the rings perhaps the bores were not within tolerance and you would have needed a rebore and oversized pistons? Did you have the bores meassured for wear to make sure you could just replace the rings?

Check the oil return pipe you can see in the photo (sometimes splits where the jubilee clip is overtightend), because i'm not sure if oil passes through that part of the turbine housing where the bolt is missing.