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Old 02-15-2010, 10:20 PM
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bulldog426 bulldog426 is offline
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Default gapping rings on kb slugs

i have kb hyperutectic slugs in my 440, i know i need to gap the top piston ring, what about the second ring?? it's a 4.32 stock bore, setting them for street nitrous in case i ever decide to put a sneeky pete or some other small shot on it, but anyway the top gap is .035, should the second ring be gapped and at what setting??
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Old 02-15-2010, 10:47 PM
rampage_82 rampage_82 is offline
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If you're going to spray it, you need to open the ring gaps even further than normal, also it's better to set up the motor a little loose in the bore too.
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Old 02-16-2010, 12:06 AM
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.035 is what kb recommends for the top ring gap for "street nitrous".. it doesn't say anything on the paper about gapping the second ring, but somebody was telling me to gap the second ring, the second ring is what i'm wondering about
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Old 02-16-2010, 02:16 AM
John Van John Van is offline
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I would go to KB's web site and see what they recomend. I would gap the second ring at the same size or bigger,There has been some talk about ring flutter if the gap is smaller,like I said check with KB
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Old 02-16-2010, 02:24 AM
DartGT66 DartGT66 is offline
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The current trend is to open the second ring end gap. If there isn't anything mentioned about the second ring end gap you could leave it as it is, or if you want to follow the current trends, open it some .005". I would also open the top ring end gap some 0.005" more for the small nitrous. The top ring takes most of the heat, usually the lower ring end gaps do not change for small amounts of nitrous. Some .023" for the second ring might work fine.
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Old 02-16-2010, 04:32 AM
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I did a cut and paste on this, but it matches a couple of very good books I have.


Most piston ring manufacturers recommend a minimum end gap of .004 inches times the bore diameter for the top piston compression ring. So for a 4 inch bore, the standard end gap would be .016 inches.

For the 2nd compression ring, the standard end gap recommendation for most stock engines is typically .005 in. x the bore diameter. So for a 4 inch bore, the minimum end gap on the 2nd ring would be .020 inches.

For a modified street performance engine that generates more horsepower and heat, the end gap should be opened up a bit to compensate for increased thermal expansion. The recommendation would be a minimum top compression piston ring end gap of.0045 to .005 inches times the bore diameter. For a 4 inch bore, the ring end gap on the top ring should be increased to .018 to .020 inches.

For the 2nd compression ring on a modified street performance engine, the recommendation is typically open up the end gap to .0055 inches times the bore diameter. For a 4 inch bore, the 2nd ring would be gapped to .022 inches.

For a nitrous or blown racing engine, the top ring end gap sould be opened up to as much as .006 or .007 inches times the bore diameter. Now we're looking at a 2nd ring end gap of .024 to .028 inches in an engine with 4 inch bores.

For the 2nd ring on a nitrous or blown motor, the recommended ring end gap is even wider: .0063 to .0073 inchestimes the bore ( or 0.025 to 0.029 inches with a 4 inch bore).

The recommended ring end gap for oil rings regardless of the engine application is typically .015 inches.

Some racers believe that opening up the 2nd end gap even more (say an additional 10%) can improve overall ring sealing by allowing trapped gases to escape before they blow past the top ring and cause ring flutter at high rpm (say above 5000 to 6000 rpm).

NOTE: These recommendations are rules of thumb only. Always follow the end gap specifications recommended by the piston ring supplier or engine manufacturer.
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Old 02-16-2010, 04:43 AM
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Just as a side note I used Childs & Alberts gapless rings, the second ring in the pic sits in behind the main ring with the gap on the opposite side.

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Old 02-16-2010, 06:28 PM
John Kunkel John Kunkel is offline
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The KB catalog states NOTE: Second ring end gaps do not need extra clearance.
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Old 02-16-2010, 08:25 PM
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Quote:
Originally Posted by bulldog426 View Post
.035 is what kb recommends for the top ring gap for "street nitrous".. it doesn't say anything on the paper about gapping the second ring, but somebody was telling me to gap the second ring, the second ring is what i'm wondering about
Always check the gap on all rings, no manufacturer is perfect. 99.9999% of the time they're good but if your luck's anything like mine.....
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Old 02-16-2010, 09:22 PM
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Check out this page: http://www.kb-silvolite.com/test/art...n=read&A_id=32
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