Not quite. Cast rings are dark,moly are lighter colored. Even if the top and second are the same color a top and 2nd ring are different. Look at the chamfer on the inner edge top or bottom. Cast rings won't last long and cost less.
Doug
Doug, please re-read my post as I think you have misunderstood what I said. A cast ring set will be the same color on the first and second ring; dark. A moly set will have a dark second ring with a lighter shiny outer facing., and a chrome set will have a dark second ring (cast) with a silver matte upper/lower side, and a shiny outer face.
A moly ring is a ductile iron ring with a coating of moly, which is porous, in order to trap oil and maintain ring lubrication. There are many different ring configurations for materials and coatings, I was just explaining some generalities. As far as the shapes go, I never said that the top and second ring are exactly the same. I was merely pointing out the colors to materials/types of ring you normally see.
Cast rings seat quickly because they are not as hard as the top ductile iron and steel rings used in top rings. Most second rings are cast as they are only a backup to help seal the chamber and keep oil in the pan. So the quicker they seat, the better they will perform. The top ring takes all of the abuse, so it is wise to have a ductile iron ring (harder), or a steel ring (imports). The moly coating holds oil to reduce cylinder wear under the extreme conditions which the ring lives. High temps, and high pressures. When the mixture fires, the top ring is pushed down, and the gas moves behind it, pushing the ring out into the cylinder wall, creating a pressure seal. This is why the cylinders were so much at the top of the piston travel.
Oil rings have been made in many different configurations over the years, from one piece, to two oil rings, to two rails with an expander. anyway, hope some of this helps someone understand the differences with rings.
