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Do I have to take care about 2nd piston ring end gap?

Posted By: NachoRT74

Do I have to take care about 2nd piston ring end gap? - 12/15/11 02:44 PM

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
Posted By: dOoC

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 02:50 PM

10 is a little TIGHT for a second ring.
Posted By: NachoRT74

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 02:55 PM

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...

Posted By: RapidRobert

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 03:33 PM

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
Posted By: MR_P_BODY

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 05:21 PM

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
Posted By: 451Mopar

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 06:10 PM

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?
Posted By: dogdays

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 06:43 PM

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.

Attached File
6968302-TB7002[1].pdf  (141 downloads)
Posted By: dOoC

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 06:48 PM

Quote:




to reduce ring flutter...






What kind of ring groove clearance specs are you seeing ?
Posted By: nomore65BelvJim

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 06:48 PM

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?
Posted By: dogdays

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 06:54 PM

Guys, take the time to read the bulletin. It's not that hard and not that long.

R.

Attached File
6968319-TB7002[1].pdf  (123 downloads)
Posted By: MR_P_BODY

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 07:58 PM

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
Posted By: Cab_Burge

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 08:14 PM

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
Posted By: Rapid340

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 08:57 PM

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

Posted By: Cab_Burge

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 09:51 PM

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
Posted By: domingo

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 10:28 PM

Yes, I also go with a little bigger gap on the second ring! Do as Cab says.
Posted By: RapidRobert

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 10:48 PM

Quote:

Do as Cab says.

I think I will (start) too
Posted By: DusterMan

Re: Do I have to take care about 2nd piston ring end gap? - 12/15/11 11:35 PM

Quote:

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



Been doing it for over 20 years.
Posted By: Performance Only

Re: Do I have to take care about 2nd piston ring end gap? - 12/16/11 12:15 PM

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.
Posted By: RapidRobert

Re: Do I have to take care about 2nd piston ring end gap? - 12/16/11 03:49 PM

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
Posted By: nomore65BelvJim

Re: Do I have to take care about 2nd piston ring end gap? - 12/16/11 10:29 PM

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.
Posted By: MR_P_BODY

Re: Do I have to take care about 2nd piston ring end gap? - 12/16/11 10:36 PM

Quote:

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.



you shouldnt see any difference in the land, its still
riding on a flat surface(ring riding on lands)
Posted By: NachoRT74

Re: Do I have to take care about 2nd piston ring end gap? - 12/17/11 05:39 AM

wow, lot of diff info coming and going.

I think will go 0.017" as the basic formula and paying attention to silvolite website saying their pistons doesn't require bigger or extra clearence at the second ring... just going to the basic
Posted By: MR_P_BODY

Re: Do I have to take care about 2nd piston ring end gap? - 12/17/11 05:45 AM

Quote:

wow, lot of diff info coming and going.

I think will go 0.017" as the basic formula and paying attention to silvolite website saying their pistons doesn't require bigger or extra clearence at the second ring... just going to the basic



have at it... stock specs will work
Posted By: NachoRT74

Re: Do I have to take care about 2nd piston ring end gap? - 12/18/11 05:28 AM

at the end, went 0.018". Some rings maybe a little bit larger ( 19 maybe? ) accidentally
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