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Old 08-27-2007, 09:06 AM
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Need Correct Ring Gap Clearance

Hello,
I have a chevy 350 that I am helping my brother rebuild. We put the crankshaft and cam in yesterday. We are getting ready to install the rings on the pistons. The motor is going in a 71 camaro that will see mostly street use. He just got it back from the machine shop, everything has been balanced. The pistons are SilvOlite hypereutectics @ 10:1 compression with 4 valve reliefs cut in the top. The rings are from Sealed Power p/n e-251k 40; 2m-139-040. The top ring is chrome moly and for high performance use they recommend gapping the top ring at .022 inch. This is all the information they give us as far as the rings are concerned. What do I gap the second ring at(second from top) , and what do I gap the 2 side rails that go with the oil expanderspacer at?

Thanks, RJD
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Old 08-27-2007, 12:27 PM
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Generally the rule of thumb is .004 for every inch of bore, so if you're at 4.030 then you would gap them at .016 -.017. But I would give it a little bit more and make the second ring .018 - .020. You'll never notice the extra and never have to worry about the ends butting. The oil rings are to be left alone, you don't need to gap them. If you're running a blower or going to use nitrous down the road then the gaps need a couple more thousands due to the excessive heat buildup.
edit...also when you file the rings, file toward the center of the ring so you don't flake off the moly facing. And file a little at a time then install in the bore and square it up with a piston to measure the ring gap. Don't leave sharp edges, just kiss it with a very fine file to chamfer the ends when gaps are correct, and keep each ring pack specific to the bore you size it to.

Last edited by 327NUT; 08-27-2007 at 12:34 PM.
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Old 08-27-2007, 02:10 PM
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more info for your specific rings (with web addresses) as a example:
http://www.stevesnovasite.com/forums...p/t-42812.html

because silvolites piston lands can be tricky...do check your specific piston on their site
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Old 08-28-2007, 01:47 AM
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Quote:
Originally Posted by newdad1
Hello,
I have a chevy 350 that I am helping my brother rebuild. We put the crankshaft and cam in yesterday. We are getting ready to install the rings on the pistons. The motor is going in a 71 camaro that will see mostly street use. He just got it back from the machine shop, everything has been balanced. The pistons are SilvOlite hypereutectics @ 10:1 compression with 4 valve reliefs cut in the top. The rings are from Sealed Power p/n e-251k 40; 2m-139-040. The top ring is chrome moly and for high performance use they recommend gapping the top ring at .022 inch. This is all the information they give us as far as the rings are concerned. What do I gap the second ring at(second from top) , and what do I gap the 2 side rails that go with the oil expanderspacer at?

Thanks, RJD
KB/UEM pistons have a specific ring end gap factor that is larger than typical.
Follow the KB UEM directions for your KB UEM pistons to the letter.
The ring end gap factor directions for KB silvolite are HERE
Do not second guess their larger than typical top ring end gap requirement.
These piston are made of a proprietory aluminum alloy (they are different)
They know that they are doing.
Your motor will not huff or smoke or have less compression or power what ever else you fear by using their recomended larger top ring end gaps. But if you don't follow their specific direction and insist on using typical cast piston ring end gaps (.016 to .020") you'll be doing it all over again. See the pictures.
The second ring gap is not near so critical. Some builders make the second ring end gap sightly bigger, some make it slightly smaller.
http://kb-silvolite.com
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Old 08-28-2007, 07:42 AM
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Hey thanks again, guys. I really appreciate the help.
Rob
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Old 08-28-2007, 07:47 AM
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your welcome...

and thanks for saying "thanks"

MOST threads poster's don't do it......it bugs me big time
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Old 08-28-2007, 03:50 PM
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The instructions that came with my KB pistons said it is better to leave a larger gap on the second ring, about .003 I think it was. The theory is that compression can get trapped between the two rings and cause them to unseat, if the lower gap is too tight.
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