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Re: Piston ring gap
[Re: Cab_Burge]
#563268
12/28/09 07:54 AM
12/28/09 07:54 AM
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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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My info came from a Stock Elimnator multi record holder back in the 90s. He also had dyno info to back it up. However his power peaks were higher than most of what I do. (shifting at 7200) I personally think there is soemthing to it and I'm a believer that the 2nd ring isn't a comression sealer at all. If it is working as one there's a problem with the top ring, the seating/breakin procedure, or cylinder wall finish and a problem with not enough end gap on the 2nd 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: Cab_Burge]
#563269
12/28/09 08:35 AM
12/28/09 08:35 AM
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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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Quote:
Quote:
Keep the ideas flowing please,Iwould like to here more on this,maybe we all can learn from each other.
Or maybe just me!!
Several of the better Hi Po machine shops with dynos in SO CA where kind enough(12 to 15 yrs. ago) to share with me there results on trying wider ring gaps on there dyno mules, wider is better  I use to use .016 on my stockers(426 M.W.) top rings and .012 on the second, after opening them up to .020 and .024 the car ran quicker and faster. And it didn't blow the push on breathers off in the burn out   
Be curious as to why the wider gaps made more power. Back to the flutter issue or maybe ring location on the pistons?? I'm sure a lot of gap issues revolve around piston material and configuration - cast, forged,hyper, gas ported, etc?
Fastest 300
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Re: Piston ring gap
[Re: Dave_S]
#563270
12/28/09 09:05 AM
12/28/09 09:05 AM
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Joined: Jan 2003
Posts: 16,941
NC
440Jim
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 16,941
NC
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Quote:
What about the oil ring rails?
Dave
Dave, the oil rings are usually pre-set by the manufacturer and don't require file fit or adjusting.
I don't think your application would have any problems with ring butting even as tight as 0.016" top and second, that is what most of us ran 20 years ago. But the 0.019-0.021" top has been shown to work better, especially with the looser second.
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Re: Piston ring gap
[Re: 440Jim]
#563272
12/28/09 10:52 AM
12/28/09 10:52 AM
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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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Part of my reasoning comes from some engines that came to me with blowby issues,and larger than what I like ring end gaps. One was a very low milage MP shortblock.But I suppose part of the problem could have been related to wall fnish,as Vic was saying. After a rehone and fresh rings,with tighter gaps,no more blowby issues. But I ended up polishing the crank also,as the finish on it was horrible,so maybe the finish hone was crap from Mopar too. 
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Re: Piston ring gap
[Re: Dunnuck Racing]
#563273
12/28/09 11:31 AM
12/28/09 11:31 AM
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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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Many of the recently rebuilt engines I know of have excessive blow by issues. I believe this is a result of too-rough a wall finish for proper ring seating and sealing. I think wall finish is more important than the perfect gap. There's more pressure loss and oil contamination from the entire circumference than the ring end gap.
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]
#563274
12/28/09 01:07 PM
12/28/09 01:07 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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Theory is great, and there is plenty of it on this topic. I try not to let it swollow up the objective - and that would be to keep the combustion chamber pressure / mix in the combustion chamber. I realize there are always trade offs, but any leakage past the first or second ring ( no matter how it occurs ) can only read negative. One of those built in leaks is ring end gap. So,IMO, you set the end gaps as tight as you can, leaving clearance for heat expansion and - a "safety margin" per my example. My piston manufacturer called for .030" top ring end gap. I set them at .032". Second ring went in at .016". I have had several overheat situations since with no ill effects.
Fastest 300
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Re: Piston ring gap
[Re: Crizila]
#563275
12/28/09 01:23 PM
12/28/09 01:23 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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Wow, lots of good reading here!. Thanks for the input.
I'm going to set mine at .020 top, .024 second and the oil rings at .015 (spec). We shall see how it works out come springtime!
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]
#563276
12/28/09 01:42 PM
12/28/09 01:42 PM
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Joined: Jul 2006
Posts: 4,595
On the south side of Nowhere
S/ST 3040
master
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master
Joined: Jul 2006
Posts: 4,595
On the south side of Nowhere
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Quote:
I'm going to set mine at .020 top, .024 second.......
That will work just fine. In my example, that's where I'd have
gapped them, except the filled block keeps the cylinder walls
from dissipating heat as it would with circulating coolant.
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minimum gap is tantamount to russian roulette! it's just a matter of time.
