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Do I have to take care about 2nd piston ring end gap? #1134423
12/15/11 10:44 AM 12/15/11 10:44 AM
Joined: Aug 2007
Posts: 6,095
Valencia, España
NachoRT74 Offline OP
master
NachoRT74  Offline OP
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Valencia, España
what you read.

I'm begining to build the 450 stroker with KB215s ( again ) after lots of problems I have being comfronting with local guys and several mistakes on machine shops.

KB website says to take care about the 1st compression ring end gap. Being 4.362" bore it looks I need 0.0283 gap. I simply filed up to 0.028" and a little bit extra of free play to fit the feelers easily, not tight ( kinda to give the 0.003" the feelers doesn't have )

Now, The 2nd compression ring. I don't remember exactly what feeler made to fit just out of curiosity, but maybe it was kinda 0.010 gap.

Do I have to take care of that ?. I know KB website doesn't specify anything about that, but wondering based on your experiences

With a Charger born in Chrysler assembly plant in Valencia, Venezuela
Re: Do I have to take care about 2nd piston ring end gap? [Re: NachoRT74] #1134424
12/15/11 10:50 AM 12/15/11 10:50 AM
Joined: Jul 2008
Posts: 30,424
Florida STAYcation
dOrk ! Offline
The village idiot's idiot
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Florida STAYcation
10 is a little TIGHT for a second ring.
Re: Do I have to take care about 2nd piston ring end gap? [Re: dOrk !] #1134425
12/15/11 10:55 AM 12/15/11 10:55 AM
Joined: Aug 2007
Posts: 6,095
Valencia, España
NachoRT74 Offline OP
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well, now I remember the mechanic made the measuring too but in mms and he told me it was a little bit more than 0.028 mms whats means around 0.011"... if that makes difference.



http://kb-silvolite.com/article.php?action=read&A_id=32

Example: 4" bore "Street Normally Aspirated" = 4" bore x .0065 = .026 top ring end gap. NOTE: Second ring end gaps do not need extra clearance. Dyno and track testing...


Last edited by NachoRT74; 12/15/11 11:00 AM.
With a Charger born in Chrysler assembly plant in Valencia, Venezuela
Re: Do I have to take care about 2nd piston ring end gap? [Re: NachoRT74] #1134426
12/15/11 11:33 AM 12/15/11 11:33 AM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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RapidRobert Offline
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Yes KB's want .0065 per inch of bore for the top ring. On the 2nd ring KB wants regular which old school was .003" per inch of bore which was used for decades then lately there was a school of thought that the 2nd ring needed more gap to let gasses that make it pass the 1st ring to escape so people were saying .004" per inch. Myself on I go w KB on the top ring and stay with the tried and true .003 on the 2nd ring. Alot of people use a larger (.004 per inch) gap on the 2nd ring gap but I do not. I gap the same way I do on solids ie for specified .025", a .024 gauge held square has no drag and a .026" has slight drag but it's not a dealbreaker

live every 24 hour block of time like it's your last day on earth
Re: Do I have to take care about 2nd piston ring end gap? [Re: NachoRT74] #1134427
12/15/11 01:21 PM 12/15/11 01:21 PM
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY Offline
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A lot of engine builders now are running the second
ring gap at a couple thou larger than the top
ring gap to reduce ring flutter... if it got past the
top ring you dont want to hold it back and cause any
flutter to both rings.... this is what I've been doing
for some time now
Re: Do I have to take care about 2nd piston ring end gap? [Re: NachoRT74] #1134428
12/15/11 02:10 PM 12/15/11 02:10 PM
Joined: May 2008
Posts: 5,399
Aurora, Colorado
451Mopar Offline
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there is a spec for second ring gap like the top ring gap, bore * ring gap factor. I don't recall the factor, but I think the gap ends up being about 0.017"? for the second ring?
Re: Do I have to take care about 2nd piston ring end gap? [Re: 451Mopar] #1134429
12/15/11 02:43 PM 12/15/11 02:43 PM
Joined: Jan 2003
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dogdays Offline
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Attached is the latest Mahle Clevite bulletin. According to them you should want the second ring gap to be larger than the top ring gap at operating temperature. They recommend 0.004" per inch of diameter. For a 4.375" ring the gap calculates to 0.018" or 0.46mm which I would round to 0.5mm. The top gap starts out bigger but the heat from the engine running causes it to close up the gap so it is smaller than the second ring gap.

R.

6968302-TB7002[1].pdf (139 downloads)
Re: Do I have to take care about 2nd piston ring end gap? [Re: MR_P_BODY] #1134430
12/15/11 02:48 PM 12/15/11 02:48 PM
Joined: Jul 2008
Posts: 30,424
Florida STAYcation
dOrk ! Offline
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Quote:




to reduce ring flutter...






What kind of ring groove clearance specs are you seeing ?
Re: Do I have to take care about 2nd piston ring end gap? [Re: MR_P_BODY] #1134431
12/15/11 02:48 PM 12/15/11 02:48 PM
Joined: Dec 2003
Posts: 16,844
Phoenix - surface of the sun
nomore65BelvJim Offline
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Quote:

A lot of engine builders now are running the second
ring gap at a couple thou larger than the top
ring gap to reduce ring flutter... if it got past the
top ring you dont want to hold it back and cause any
flutter to both rings.... this is what I've been doing
for some time now





that makes sense

have you noticed any differences since you started doing this?
Re: Do I have to take care about 2nd piston ring end gap? [Re: dogdays] #1134432
12/15/11 02:54 PM 12/15/11 02:54 PM
Joined: Jan 2003
Posts: 16,376
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dogdays Offline
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Guys, take the time to read the bulletin. It's not that hard and not that long.

R.

6968319-TB7002[1].pdf (121 downloads)
Re: Do I have to take care about 2nd piston ring end gap? [Re: nomore65BelvJim] #1134433
12/15/11 03:58 PM 12/15/11 03:58 PM
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY Offline
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Quote:

Quote:

A lot of engine builders now are running the second
ring gap at a couple thou larger than the top
ring gap to reduce ring flutter... if it got past the
top ring you dont want to hold it back and cause any
flutter to both rings.... this is what I've been doing
for some time now





that makes sense

have you noticed any differences since you started doing this?



I cant say for fact due to I dont dyno my engines
and usually it isnt quite the same set up
Re: Do I have to take care about 2nd piston ring end gap? [Re: nomore65BelvJim] #1134434
12/15/11 04:14 PM 12/15/11 04:14 PM
Joined: Aug 2003
Posts: 43,173
Bend,OR USA
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Cab_Burge Offline
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Quote:

Quote:

A lot of engine builders now are running the second
ring gap at a couple thou larger than the top
ring gap to reduce ring flutter... if it got past the
top ring you dont want to hold it back and cause any
flutter to both rings.... this is what I've been doing
for some time now





that makes sense

have you noticed any differences since you started doing this?

I know one of the best Hi Po machine shops and high end engine building shops in SO CA that use the 2nd gap bigger(.002 to .004) than the top gap policy I have also for the last ten years I started that when TRW, Speed Pro started recommending that procedure

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Do I have to take care about 2nd piston ring end gap? [Re: Cab_Burge] #1134435
12/15/11 04:57 PM 12/15/11 04:57 PM
Joined: Sep 2004
Posts: 2,091
oberlin, Ohio
Rapid340 Offline
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It is worth half a tenth for an average street/strip car.


1971 Factory Appearing Duster 340 11.000 @ 122 mph
Re: Do I have to take care about 2nd piston ring end gap? [Re: Rapid340] #1134436
12/15/11 05:51 PM 12/15/11 05:51 PM
Joined: Aug 2003
Posts: 43,173
Bend,OR USA
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Cab_Burge Offline
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Quote:

It is worth half a tenth for an average street/strip car.



who knows, I don't I do know that when the rings touch (due to having to small rung gaps) and flutter the car slows down a bunch and you have to go thruogh the motor (rering and hone) to fix it The car doesn't slow down when the gaps are correct, remember a street car on pump gas that has to be driven in the rain and the heat of summer is a lot different animal than a dedicated drag car on race gas Wider is better when it comes to ring gaps on the street My pump gas 518 C.I. 1971 Duster has ran 9.99 on pump gas motor only with .022 to .024 top gap and .026 to .028 second ring gap in a 4.375 bore

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Do I have to take care about 2nd piston ring end gap? [Re: NachoRT74] #1134437
12/15/11 06:28 PM 12/15/11 06:28 PM
Joined: Jan 2003
Posts: 9,670
Lima, Peru
domingo Offline
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Yes, I also go with a little bigger gap on the second ring! Do as Cab says.
Re: Do I have to take care about 2nd piston ring end gap? [Re: domingo] #1134438
12/15/11 06:48 PM 12/15/11 06:48 PM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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RapidRobert Offline
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Quote:

Do as Cab says.

I think I will (start) too

live every 24 hour block of time like it's your last day on earth
Re: Do I have to take care about 2nd piston ring end gap? [Re: RapidRobert] #1134439
12/15/11 07:35 PM 12/15/11 07:35 PM
Joined: Jan 2003
Posts: 644
Warner Robins, Georgia
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DusterMan Offline
super street
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Quote:

I started that when TRW, Speed Pro started recommending that procedure



Been doing it for over 20 years.

Pete:
2003 Dodge Quad 2500 Hemi
69 RoadRunner 4 sp Alpine White
2019 Dodge Charger
Re: Do I have to take care about 2nd piston ring end gap? [Re: DusterMan] #1134440
12/16/11 08:15 AM 12/16/11 08:15 AM
Joined: Jul 2010
Posts: 2,091
Delray beach, Florida
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Performance Only Offline
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if you gapped the top and second rings the same, the second ring gap will be larger in a running engine since it never see's the flame front and heat that the top ring will see.
another consideration is the material the rings are made of. different materials have different expansion rates. a top ductile iron ring is more dense than a cast iron second ring.
unless you have years of experience using all types of ring materials in varying applications to fall back on, your best bet is to follow the manufacturers recommendations regarding end gap. the only exception to that is when using the KB pistons it is imperative that you follow their top ring gap instructions instead.

machine shop owner and engine builder
Re: Do I have to take care about 2nd piston ring end gap? [Re: Performance Only] #1134441
12/16/11 11:49 AM 12/16/11 11:49 AM
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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RapidRobert Offline
Circle Track
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Lincoln Nebraska
Quote:

when using the KB pistons it is imperative that you follow their top ring gap instructions instead.

No doubt about that , that caveat is set in stone

live every 24 hour block of time like it's your last day on earth
Re: Do I have to take care about 2nd piston ring end gap? [Re: MR_P_BODY] #1134442
12/16/11 06:29 PM 12/16/11 06:29 PM
Joined: Dec 2003
Posts: 16,844
Phoenix - surface of the sun
nomore65BelvJim Offline
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Quote:

Quote:

Quote:

A lot of engine builders now are running the second
ring gap at a couple thou larger than the top
ring gap to reduce ring flutter... if it got past the
top ring you dont want to hold it back and cause any
flutter to both rings.... this is what I've been doing
for some time now





that makes sense

have you noticed any differences since you started doing this?



I cant say for fact due to I dont dyno my engines
and usually it isnt quite the same set up




I was thinking more of a difference in the wear and tear on the rings and grooves/lands.

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