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Old 01-29-2010, 12:55 PM   #1
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Default Ring end gap

Supertech pistons, first overbore, 9.5:1, going to run ~15+ psi boost. Supertech says .021 top, .023 bottom compression rings. Do I run this, or run them closer? They are tight now, so I have lots of options. I will probably cross-post this on m.net if nothing shows up here.
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Old 01-29-2010, 01:09 PM   #2
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Originally Posted by webby459 View Post
Supertech pistons, first overbore, 9.5:1, going to run ~15+ psi boost. Supertech says .021 top, .023 bottom compression rings. Do I run this, or run them closer? They are tight now, so I have lots of options. I will probably cross-post this on m.net if nothing shows up here.
Do NOT run tight ring gaps on a forced induction or nitrous motor! The rings expand under load and can actually butt ends and cause ring/land failure. Rule of thumb on blown motors is .006" end gap per inch of bore diameter on the top ring and .005" on the second ring. This equates to .020 on the top and .017 on the second. If Supertech is suggesting .021 top and .023 bottom for your pistons in a turbo application, do not run any less end gap. Use a piston ring filing tool carefully, and check clearance by putting the ring in the bore and squaring it with the head of a piston. Each ring needs to be filed for a specific bore and kept organized so it gets installed in that bore. Use a small file to deburr the ends of the rings after you have them file fit to the proper clearances.
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Old 01-29-2010, 01:27 PM   #3
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What he said.

I bought a ring end filer for this. ~$60 shipped.
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Old 01-29-2010, 01:32 PM   #4
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Do NOT run tight ring gaps on a forced induction or nitrous motor! The rings expand under load and can actually butt ends and cause ring/land failure. Rule of thumb on blown motors is .006" end gap per inch of bore diameter on the top ring and .005" on the second ring. This equates to .020 on the top and .017 on the second. If Supertech is suggesting .021 top and .023 bottom for your pistons in a turbo application, do not run any less end gap. Use a piston ring filing tool carefully, and check clearance by putting the ring in the bore and squaring it with the head of a piston. Each ring needs to be filed for a specific bore and kept organized so it gets installed in that bore. Use a small file to deburr the ends of the rings after you have them file fit to the proper clearances.
$MONEY$

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What he said.

I bought a ring end filer for this. ~$60 shipped.
I bought an engine builder for this.
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Old 01-29-2010, 01:32 PM   #5
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What he said.

I bought a ring end filer for this. ~$60 shipped.
Do they take material off fairly quickly?
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Old 01-29-2010, 01:37 PM   #6
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You should have gotten a sheet with your pistons that says what endgaps to run based on your intended use. If you don't have it, call Supertech and they'll email it to you. It's a multiplier based on street/roadcourse/drag/nitrous/etc use.
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Old 01-29-2010, 01:38 PM   #7
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Do they take material off fairly quickly?
Fast enough that you can take off too much if you don't check frequently. They also file the ring end perfectly square which is difficult to do if you haven't done it before. Goggle ring end gap filing and you should pull up some U-Tube videos.
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Old 01-29-2010, 01:39 PM   #8
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I dislike the cheap ring filers. I use a diamond coated knife sharper. It is very quick and easy.
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Old 01-29-2010, 02:27 PM   #9
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I dislike the cheap ring filers. I use a diamond coated knife sharper. It is very quick and easy.
Very slick!!! I've got a 3/4" x 5" Gatco diamond hone for knives that should work on rings if I put it upright in a vice. I've got 8 old BP compression rings to practice on before I start on the new rings so hopefully I won't screw up the new rings.
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Old 01-29-2010, 03:05 PM   #10
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The filer I bought is the same one my machinist uses.
It removes material very quickly thus one has to be careful about removing too much.

After using the filer, the edges have to be dressed with a very fine wet knife sharpening stone.
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Old 01-29-2010, 03:20 PM   #11
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This is why I use the diamond sharpener. Its hard enough to cut any metal quickly, but fine enough that I don't need to go behind it with anything. I just got the fine version from Lowes. I don't remember how makes it.
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Old 01-29-2010, 03:41 PM   #12
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Just follow the sizing chart they give you with the pistons. I did my wisecos at .017 for the top ring and .019 for the bottom ring. Oil rings didnt need any sizing. For example i did the .060 overbore on my 1.6, the bore size is 3.1299, follow the chart for the proper application (street moderate turbo/nitrous) .0055 x 3.1299 = .017ish(top ring) and .0060 x 3.1299 = .019ish(bottom ring). Just follow manufacturers specs, figure they've been making pistons for longer then ive been alive so they must know best. Be careful gapping too big as well, you'll have a smoke'mobile.
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Old 01-29-2010, 04:37 PM   #13
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Originally Posted by JasonC SBB View Post
The filer I bought is the same one my machinist uses.
It removes material very quickly thus one has to be careful about removing too much.

After using the filer, the edges have to be dressed with a very fine wet knife sharpening stone.
Jason,

Did you get the motorized ring filer or the hand crank ring filer??
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Old 01-29-2010, 04:46 PM   #14
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Well this is serendipitous, I was just about to post the exact same thread.

I bought the NPR rings from eGay and found they had about a .012-.014" end gap which was slightly larger than the old rings I pulled from y8s old pistons. I was about to kick off at the seller.

My engine is only NA but will still be making a bit more power than stock so is .012-.014" ok? My overhaul manual states between .006" and .009" as standard and a maximum (your engine is shot if you get to this point) of .036".
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Old 01-29-2010, 04:46 PM   #15
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60 bucks I'm guessing hand crank
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Old 01-29-2010, 05:28 PM   #16
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Jason,

Did you get the motorized ring filer or the hand crank ring filer??
Hand crank.

I once did it by hand as neo suggests, and it took FOREVER and I ended up FILING MY FINGERNAILS AND FINGERTIPS TOO.
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Old 01-29-2010, 05:52 PM   #17
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Hand crank.

I once did it by hand as neo suggests, and it took FOREVER and I ended up FILING MY FINGERNAILS AND FINGERTIPS TOO.
Let us know how that works out for you. Summit has those for a pretty good price; I'm just wonder how hard it is to gently squeeze the ring with one hand while rotating the crank with the other. Kind of like rubbing your stomach and patting your head at the same time.
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Old 01-29-2010, 06:12 PM   #18
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I believe I bought it from this store, and this is the brand I got.
I'll bolt it to my bench or squeeze it in my vise.
Right hand to turn crank, left hand to hold ring and squeeze it against disk.
No harder than holding a magazine with the left hand and jacking off with the right.
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Old 01-28-2012, 10:07 PM   #19
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classic, was just reading through this thread and that final post just made it lol
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