Piston Ring Choices ???
#1
07-07-2005, 12:34 AM
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#2
07-07-2005, 09:00 AM
More Turbo
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As you might expect, there are pros & cons to each type.
Cast iron:
Pros- cheap, made in virtually any size, easily obtainable almost anywhere, forgiving as to break-in
Cons- don't necessarily provide the optimum bore seal for high-performance applications, longevity can be a problem (depends on a number of factors)
Moly: (which are cast rings with a channel, into which moly is "sprayed")
Pros: very effective ring seal WHEN broken in properly, cause less bore wear, more resistant to high temperatures, longer life
Cons: more expensive, not always available in weird bore sizes (normally not much of an issue, but some orphan engines may not have the moly option), moly coating is fairly easy to chip on installation if you are not careful, break in procedure is crucial
Three final things I would add, my opinions only.
1) I've built over a hundred engines so far, ranging from stock to tractor pulling. I use moly rings almost exclusively, even in dirt cheap "claimer" engines. I lean towards Speed-Pro/Sealed Power, but Hastings, Perfect Circle, etc. are good too. I haven't used plain cast iron rings since the mid '80s.
2) With any kind of ring, but especially moly, break-in is important. The biggest mistake people make is to "baby" the engine for the first "thousand or so miles" (or 500, or 200-, whatever). This easy driving will smooth over the ridges left by the honing pattern & the rings will be more difficult to seat, or may never seat. Since moly rings require a much finer cyl. wall finish, they are more susceptible to this. Once the initial cam break-in is done, & the oil/filter has been changed, you should run the engine through the gears (under a load, in other words) fairly hard up to about 60 mph or so, then let it coast back down. Repeat about 4-5 times. It doesn't need to be 8000 rpm blasts,
but don't baby it either. It will likely smoke some at first. It needs the gas pressure to help seat the rings.
3) Make sure the machine shop knows what type of rings you plan to use, before they hone it. If they don't even ask.....I'd be worried.
Cast iron:
Pros- cheap, made in virtually any size, easily obtainable almost anywhere, forgiving as to break-in
Cons- don't necessarily provide the optimum bore seal for high-performance applications, longevity can be a problem (depends on a number of factors)
Moly: (which are cast rings with a channel, into which moly is "sprayed")
Pros: very effective ring seal WHEN broken in properly, cause less bore wear, more resistant to high temperatures, longer life
Cons: more expensive, not always available in weird bore sizes (normally not much of an issue, but some orphan engines may not have the moly option), moly coating is fairly easy to chip on installation if you are not careful, break in procedure is crucial
Three final things I would add, my opinions only.
1) I've built over a hundred engines so far, ranging from stock to tractor pulling. I use moly rings almost exclusively, even in dirt cheap "claimer" engines. I lean towards Speed-Pro/Sealed Power, but Hastings, Perfect Circle, etc. are good too. I haven't used plain cast iron rings since the mid '80s.
2) With any kind of ring, but especially moly, break-in is important. The biggest mistake people make is to "baby" the engine for the first "thousand or so miles" (or 500, or 200-, whatever). This easy driving will smooth over the ridges left by the honing pattern & the rings will be more difficult to seat, or may never seat. Since moly rings require a much finer cyl. wall finish, they are more susceptible to this. Once the initial cam break-in is done, & the oil/filter has been changed, you should run the engine through the gears (under a load, in other words) fairly hard up to about 60 mph or so, then let it coast back down. Repeat about 4-5 times. It doesn't need to be 8000 rpm blasts,
but don't baby it either. It will likely smoke some at first. It needs the gas pressure to help seat the rings.3) Make sure the machine shop knows what type of rings you plan to use, before they hone it. If they don't even ask.....I'd be worried.
#3
07-07-2005, 09:11 AM
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