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Piston ring gap
#563248
12/26/09 03:04 PM
12/26/09 03:04 PM
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Joined: Jan 2003
Posts: 344
Burlington, Ontario Canada
Dave_S
OP
enthusiast
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OP
enthusiast
Joined: Jan 2003
Posts: 344
Burlington, Ontario Canada
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I was just reading on ClassRacer.com about ring end gaps. Some of the posters were recommmending the second ring gap should be double that of the first. My TotalSeal instructions call for .019 top and .016 second (1/16 moly top, iron 2nd) What is your opinion/experience?
Also what about the oil ring gap?
Thanks
Dave
Dave Stillie
'73 Swinger
5.7 Hemi, 88mm turbo, powerglide, cal-tracs & 8 3/4
Mega-Squirt EFI
[email]8.93@149
[/email]
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Re: Piston ring gap
[Re: Dave_S]
#563249
12/26/09 03:16 PM
12/26/09 03:16 PM
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Joined: Nov 2003
Posts: 6,293
Rock Springs
Bob_Coomer
master
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master
Joined: Nov 2003
Posts: 6,293
Rock Springs
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Here is my  I dont under stand why such the extra wider ring gap for the 2nd ring. I can under stand a few thousands extra yes. But this would occur anyways. Example, Gap the top ring .020 and gap the 2nd ring .020..the top ring will see more heat and expansion by nature. That why I dont think it would hurt to gap them the same, the top ring will have a hair less gap from expansion anyways. I have had engine slobber, blow oil, smoke like a freight train at the track, pull it apart, hone the block, file fit the rings, really give it a good work over... back at the track, no more slobbering, blowing oil out the dip stick after a pass...Guess what though? The car runs the same, all that was worth zero power. Its nice not to be blowing oil and to keep oil out of the combustion chamber. The main thing is to get good ring seal, and keep them from butting, .005 in ring gap either way doesn't mean crap. Gap them both about .004-.0045 for a N/A engine and dont look back
Last edited by Bob_Coomer; 12/26/09 03:18 PM.
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Re: Piston ring gap
[Re: 440Jim]
#563254
12/27/09 12:16 PM
12/27/09 12:16 PM
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Joined: Jan 2003
Posts: 344
Burlington, Ontario Canada
Dave_S
OP
enthusiast
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OP
enthusiast
Joined: Jan 2003
Posts: 344
Burlington, Ontario Canada
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Bore 4.375, N/A, no nitrous,EFI with gas. Looks like Im OK with the top ring specs. I will prob. open up the second ring gap as suggested. That chart Jim is the something new. It's not the one that came with my ring set. What about the oil ring rails?
Dave
Dave Stillie
'73 Swinger
5.7 Hemi, 88mm turbo, powerglide, cal-tracs & 8 3/4
Mega-Squirt EFI
[email]8.93@149
[/email]
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Re: Piston ring gap
[Re: 440Jim]
#563255
12/27/09 12:35 PM
12/27/09 12:35 PM
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Joined: Feb 2003
Posts: 12,675
Columbia, CT
moper
I Live Here
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I Live Here
Joined: Feb 2003
Posts: 12,675
Columbia, CT
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The second ring is not a compression ring by design. It's just an oil scaper. The issue is the top ring, the only compression ring, seals on the bore AND the piston ring land. It seals on the up and down stroke. So there can be gasses between the top and second rings. These gasses can push the ring up off the ring land and the result is not ring flutter but simple loss in seal efficiency on the compression stroke. That's why the gap is larger. Add extra oil to the walls and I think the problem gets worse. I generally add .006 to the 2nd ring gap for a small block, and .008 for a big block. Again, this ring isnt designed to seal gasses but it can trap gasses when doing it's real job. So a larger gap has no effect on compression loss. Just a loss of sealing efficiency to the top ring.
Well, art is art, isn't it? Still, on the other hand, water is water! And east is east and west is west and if you take cranberries and stew them like applesauce they taste much more like prunes than rhubarb does. Now, uh... Now you tell me what you know.
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Re: Piston ring gap
[Re: moper]
#563256
12/27/09 01:56 PM
12/27/09 01:56 PM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
master
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master
Joined: Oct 2003
Posts: 7,506
Az
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I think KB has done a good job of addressing pressure spikes ( top ring flutter ) with their "accumulator groove" ( between the top and second rings ) design on their Hypo pistons. Remember any oil that gets in to the combustion chamber ( via the rings or the valve guides )can have very negative affects on the octane number ( reads detonation ). Those of you that run on the edge for pump gas, this can mean broken parts. Oil in the mix can have much more serious affects than getting the quench right.
Fastest 300
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Re: Piston ring gap
[Re: Crizila]
#563257
12/27/09 03:26 PM
12/27/09 03:26 PM
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Joined: Mar 2007
Posts: 3,300
Northern Indiana
Dunnuck Racing
master
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master
Joined: Mar 2007
Posts: 3,300
Northern Indiana
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I'll go ahead and throw my opinion in here too,..
If you have combustion gasses getting past the top ring (enough to cause ring flutter,etc.),why on earth loosen up the second ring gap and let it blow into the crancase?
I would rather run a little tighter ring gap on the top ring and not let as much pressure get past it to begin with.
If you stay within reason,and don't push temps with too much timing,insufficient fuel,etc.it won't be a problem.
Again,just my opinion,It is obvious that oter builders do things for different reasons.
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Re: Piston ring gap
[Re: Dunnuck Racing]
#563261
12/27/09 08:56 PM
12/27/09 08:56 PM
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Joined: Dec 2008
Posts: 1,200
UK
602heavy
pro stock
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pro stock
Joined: Dec 2008
Posts: 1,200
UK
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The 2nd ring does'nt really care what gap it's running , what about the guys that don't run a 2nd ring? , the 2nd is an oil scraper , there's no reason not to open 2nd ring , there's always going to be pressure build up between top & 2nd even when running tight top ring gap , why not let the pressure escape? , i only see a positive regards this approach & no negative , but we all have different opinions which should be respected , i'd rather run the larger 2nd ring for above reasons , the added bonus for myself running nitrous would be cooling the underside of piston due to increased oil scavenge back to pan. 
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Re: Piston ring gap
[Re: Crizila]
#563263
12/27/09 09:23 PM
12/27/09 09:23 PM
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Joined: Mar 2007
Posts: 3,300
Northern Indiana
Dunnuck Racing
master
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master
Joined: Mar 2007
Posts: 3,300
Northern Indiana
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Well,to explain myself a little more clearly,I beleive that the 2nd ring should be tighter than the 1st ring.The second ring is designed to be a scraper ring primarily,but it does have some sealing properties as well.If it did not,Total seal probably would not offer a gapless second ring option. That being said,I would rather open the first ring up more to let trapped pressure back in the chamber,rather than have it blow by into the crankcase. On the no second ring deal,I think it is a tossup. Similar to running low tension oil rings,etc.Most of those need to run a vacuum pump to help keep crancase pressure to a minimum.All in an effort to get less ring drag,or due to rod length/pin height issues  Keep the ideas flowing please,Iwould like to here more on this,maybe we all can learn from each other. Or maybe just me!!
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Re: Piston ring gap
[Re: Cab_Burge]
#563264
12/27/09 09:33 PM
12/27/09 09:33 PM
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Joined: Oct 2003
Posts: 7,506
Az
Crizila
master
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master
Joined: Oct 2003
Posts: 7,506
Az
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As per Cabs comment, this is exactly why you want to leave yourself a little margin for error. If you look directly under the license plate in the pic, you can see my water pump belt exiting, stage left. Decided to make the pass anyway. Couldn't get all the way back to my pit area though, as the temp gauge was passing 250 by the ET shack. Glad I had the top rings gapped a couple thousands larger than called for.
Fastest 300
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Re: Piston ring gap
[Re: Crizila]
#563265
12/27/09 09:49 PM
12/27/09 09:49 PM
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Joined: Mar 2007
Posts: 3,300
Northern Indiana
Dunnuck Racing
master
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master
Joined: Mar 2007
Posts: 3,300
Northern Indiana
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My 4.375 bore is run with .017 top,.013 second end gaps.After several years of racing and a few overheating episodes due to burnt up pump drive motors and occasional wiring issues,never had a ring butting issue. Maybe I am just lucky,but you wouldn't say that if you knew me. But as stated before,everyone has their reasons and theories,and should be respected for them! 
Last edited by Dunnuck Racing; 12/27/09 11:07 PM.
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) It is now recommended by most of the better ring companys and engine builders to make he 2nd ring a little looser(.001 per inch of bore size or so) than the top ring, IE top ring .004 per inch of bore and 2nd ring .005 per inch of bore 
Once you butt a ring you will never advocate that theory again 
It's way better to be .002 to .003 to wide than .0002 to tight 
100% on that - and that's exactly what I do with the top ring - go with the piston manufacturers recommendation and add .002" - top ring only. I consider that to be as close I can get away with. On the second ring I almost always go with the .004" per inch of bore rule.
