[drmustang68]

Can anyone summarize the advantages and disadvantages of using each type of rings in an engine rebuild (cast, moly coated, chrome)?


Thanks in advance.
Drmustang68

 

[brianj5600]

Cast iron rings are cheap. Ok for a grocery getter, but not used for performance engines.

Moly tolerates more heat and more durable. Most performance engines use them.

Chrome rings are very hard and take major abuse, but abuse cylinders in the process.

 

[silverbandit]

All rings (typical automotive purposes) are cast rings with various coatings. The most common are Chrome and Moly rings. Basic cast rings break in quick - great for the Mom and Pop grocery getter.

Chrome has excellant abrasive wear properties
(carbon, dust) but break in slower. It is a very hard coating. It is not a good choice when running propane (on a 390?).

Moly rings have a high melting point (4800F), therefore resisting scuffing. Scuffing is the 'welding' of the ring to the cylinder at TDC of the power stroke. Yep, it gets that hot in there! Moly rings also have a porous surface that holds a little oil and they break in fast.

There are also rings with Molybdenum Oxide, Tungsten and Titanium carbide but typically for racing only.

I would look at buying Moly rings, it's usually not a whole lot more expensive. Make sure the machinist knows the rings you're using because the cylinders require a different final honing for types of rings.

 

[gotstang]

Moly has also been used an a lot of production engines since 1985 or so and moly rings are one reason the 5.0s last so long. IIRC the 5.0 rings are low tension as well which is a plus, get those if you can.

 

[silverbandit]

Now that's funny, two post's at the same time that use 'grocery getter ' in the reply!

 

[maloofracing]

Ford and GM both have used a Moly top ring in their engines since the 60's. The GM top ring was also made out of Ductile material. The Ductile material is virtually unbreakable. You can twist them around and around and they will not break. That is the most common ring I use in my engines.

Do not, and I repeat, Do not use any kind of gapless ring. The TS and Childs and Albert rings do not do a good job of sealing an engine. You will be sorry if you try them. My ring of preference is Speed Pro, or sealed power.