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engineguy · 03-02-2019, 11:50 PM

The coating is much different on grey cast iron top rings versus Ductile iron top rings.
First of all the Ductile iron (or steel) top rings are much stronger and will provide much more service life than the grey iron rings will. Grey iron and Ductile iron top rings are both available with Moly face material, but the difference is that the gray iron ring has a groove machined in the face and then this groove and surrounding ring face is filled with molten Moly and then finished to size.
Good quality high performance top rings will be Ductile iron with plasma-sprayed Moly, then the ring faces are finished to size and barrel-faced in a manderal. The moly material on the top ring adds some lubricity and will allow the ring to conform more closely to the cylinder finish, but the moly applied to the grey iron ring is prone to being hammered out under severe usage, especially the slightest hint of detonation or pre-ignition.
Save yourself some frustration and purchase good quality rings with sprayed plasma Moly top rings for any high performance application.

03-02-2019, 11:50 PM	#6
engineguy Junior Member Join Date: Jan 2003 Location: Gold Canyon, AZ Posts: 12 Likes: 0 Liked 1 Time in 1 Post	Re: question on rings ? The coating is much different on grey cast iron top rings versus Ductile iron top rings. First of all the Ductile iron (or steel) top rings are much stronger and will provide much more service life than the grey iron rings will. Grey iron and Ductile iron top rings are both available with Moly face material, but the difference is that the gray iron ring has a groove machined in the face and then this groove and surrounding ring face is filled with molten Moly and then finished to size. Good quality high performance top rings will be Ductile iron with plasma-sprayed Moly, then the ring faces are finished to size and barrel-faced in a manderal. The moly material on the top ring adds some lubricity and will allow the ring to conform more closely to the cylinder finish, but the moly applied to the grey iron ring is prone to being hammered out under severe usage, especially the slightest hint of detonation or pre-ignition. Save yourself some frustration and purchase good quality rings with sprayed plasma Moly top rings for any high performance application.