FE Power Forums
FE Power Forums => FE Technical Forum => Topic started by: fe66comet on August 23, 2014, 04:57:34 PM
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I see two sets of rings available for my 390. One has a gapless top ring and standard second which is the route I have always gone, another is a gapless second with a standard first. What is a better route for the street? I am going standard tension on the oil rings also.
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Conventional on both rings....
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Gapless rings are for air compressors and catalogs.
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I'll throw the 3rd strike........go conventional, then the pressure help the rings not fight them
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I always ran them on my two stroke bikes, I definitely got a boost there. On their site they claim 30 HP on a small block 350, I was just thinking a little kick in the butt would not hurt, while I have it apart. Has anyone had a bad experience with them?
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Why does everybody hate gapless rings?
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Because they don't work as advertised. They don't seal as well as a good conventional ring set.
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I'll take that as a bad investment, so what would be a good set for high compression and a lot of street time? Is molly a good option and just file fit? I have used a lot of chrome iron but not at 11:1 compression.
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Moly all the way, just be sure to put on the right cross-hatch/finish for moly rings! Note the "almost universal use of moly rings.....". Truck diesels and dirt track engines are the only users left of the old school chrome rings.
http://www.enginebuildermag.com/1997/07/piston-rings-and-surface-finish/
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You just need a regular set of Total Seal or Mahle piston rings. Moly faced top ring, standard tension, Napier 2nd if you want to get fancy. Depending on your bore size, you can get a file fit, or get a drop-in set, check the gaps, dress the ends, and go.
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I am thinking steel gas nitrate on top, it will hold up to the 11:1 compression, conforms to the cylinder better and lasts for 200,000 miles. Second a nodular iron Napier then a couple stainless oil rings.
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You're over thinking it
A plasma-moly faced top ring on either a steel or ductile iron base is perfectly fine. Once upon a time I was providing that exact material and face coating to Pro Stock and Cup teams - you simply do not need anything else.
A cast second ring is equally fine. Napier or a back cut (reduced radial wall thickness) will reduce cross section and free up a few horsepower if you feel the need to get swoopy.
All the oil rails in most everybody's quality sets are steel with a chrome face. All the expanders are stainless - Speed-Pro uses the SS50U design with bumps going "in and out", the rest use a Hastings expander with bumps going "up & down". I can make a sound argument for both designs. If you want to reduce friction you can go to a reduced radial wall thickness here as well.
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Mostly reducing friction and durability is what I am after. I would not do anything without sound reasoning behind it.