Previous Thread
Next Thread
Print Thread
Page 2 of 4 1 2 3 4
Re: Ring Gap #23777
04/23/06 01:31 PM
04/23/06 01:31 PM
Joined: Aug 2003
Posts: 43,007
Bend,OR USA
C
Cab_Burge Offline
I Win
Cab_Burge  Offline
I Win
C

Joined: Aug 2003
Posts: 43,007
Bend,OR USA
as one old f--- to another I use .020 to .022 on the top with any bore over .4.3 and .024 to .028(depending on the exact application of the motor and its induction system or power adders and so on) on the second rings. Looser ia always better than to tight on a race engine, especially on ring gaps! My 512 stroker 400 block (9.25 to 1 comp. on pump gas) makes 609 hp on the DTS engine dyno at 5600 rpm with ported 906 heads.


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Ring Gap [Re: Cab_Burge] #23778
04/23/06 02:44 PM
04/23/06 02:44 PM
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
B
BradH Offline
Taking time off to work on my car
BradH  Offline
Taking time off to work on my car
B

Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
I'm familiar with the trend to run a wider second gap than the first to keep pressure from being trapped between the two rings. But if you take into account that the top ring gap is going to close up more due to being exposed to more direct heat from the combustion chamber, I'd expect setting the gaps the same should have the same effect once the engine is running.

And why would the gap need to be any bigger than the top gap under running conditions, since the only point of this approach is to make sure there is no excess pressure build-up between the two rings that causes the top ring to lose seal? As long as the running gaps are the same, that should result in an equal sized "path" for any unwanted pressure build-up to escape, right? Any larger gap than the effective running gap of the top ring seems like more than is needed to my way of thinking...

Re: Ring Gap [Re: BradH] #23779
04/23/06 04:11 PM
04/23/06 04:11 PM

A
Anonymous OP
Unregistered
Anonymous OP
Unregistered
A



brad, in theory your thoughts have some merit. But, under combustion pressure you don't want equal paths. if that's all you have then pressure builds between the rings and the unseating occurs. you can think of each gap as a restrictor, or orifice. the 2nd needs to be larger than the first to keep presssure buildup down.

Re: Ring Gap #23780
04/23/06 05:27 PM
04/23/06 05:27 PM
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
B
BradH Offline
Taking time off to work on my car
BradH  Offline
Taking time off to work on my car
B

Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
Quote:

...you can think of each gap as a restrictor, or orifice. the 2nd needs to be larger than the first to keep presssure buildup down.



I still don't understand why it would behave any differently with a bigger 2nd gap than a same-size 2nd gap... If the second gap is the same size as the first, then the pressure will escape just as quickly as the first gap can let it in.

The first gap is the initial restrictor; as long as the second gap is at least as big as the first, there shouldn't be any pressure build-up. If there is, then something else is going on that's not being taken into account by simple ring gap math comparisons, such as additional blow-by getting past the ring-to-cylinder contact area, in addition to what would be expected to get through the ring gap.

Re: Ring Gap [Re: BradH] #23781
04/23/06 05:48 PM
04/23/06 05:48 PM

A
Anonymous OP
Unregistered
Anonymous OP
Unregistered
A



Quote:

I still don't understand why it would behave any differently with a bigger 2nd gap than a same-size 2nd gap... If the second gap is the same size as the first, then the pressure will escape just as quickly as the first gap can let it in.




I don't believe that to be true. ANY pressure buildup will result in unseating the top ring from the ring land. even the piston companies have gotten involved by putting pressure equalization channels between the two top rings to try and help this particialr problem.
I don't think i can expalin it any better than i already have. most ring manufacturers tell you to open the 2nd ring gap now. my experiences over the years have been that opening the 2nd ring gap helps make more power. every engine builder that i know personally does it that way also. I don't think we're all wrong in what we do with regards to ring gaps.

Re: Ring Gap #23782
04/23/06 06:19 PM
04/23/06 06:19 PM
Joined: Jan 2003
Posts: 5,484
SoCal
Brian Hafliger Offline
master
Brian Hafliger  Offline
master

Joined: Jan 2003
Posts: 5,484
SoCal
Only way to know for sure is try it for yourself!!

I certainly dont get any credit or kick back from anyone so my advice is not biased but hard earned I can tell ya that!

Brian

Re: Ring Gap [Re: Brian Hafliger] #23783
04/23/06 09:42 PM
04/23/06 09:42 PM
Joined: Jan 2003
Posts: 549
Bristol, Va
fasteddie Offline
mopar
fasteddie  Offline
mopar

Joined: Jan 2003
Posts: 549
Bristol, Va
Very interesting thread

Here is the reccomended gaps from Keith Black Pistons. They say the second ring doesn't need a different gap than the top.

http://kb-silvolite.com/clearance_pop.php


2003 Bristol Dragway Sportsman Champion

2016 Bristol Dragway Power Hour Champion
Re: Ring Gap [Re: fasteddie] #23784
04/23/06 11:56 PM
04/23/06 11:56 PM
Joined: Jan 2005
Posts: 1,260
Las Vegas NV
moparmanjames Offline
pro stock
moparmanjames  Offline
pro stock

Joined: Jan 2005
Posts: 1,260
Las Vegas NV
Quote:

Very interesting thread

Here is the reccomended gaps from Keith Black Pistons. They say the second ring doesn't need a different gap than the top.

http://kb-silvolite.com/clearance_pop.php




And...what about gapless second rings, as I mentioned before? Are they crap?

Re: Ring Gap [Re: moparmanjames] #23785
04/24/06 12:50 AM
04/24/06 12:50 AM
Joined: Jan 2003
Posts: 5,484
SoCal
Brian Hafliger Offline
master
Brian Hafliger  Offline
master

Joined: Jan 2003
Posts: 5,484
SoCal
Quote:

And...what about gapless second rings, as I mentioned before? Are they crap?




IMO...Yes! Gapless tops work well in Alky app's but other than that I wouldn't use them.
C'ourse what do I know...?

Re: Ring Gap [Re: Brian Hafliger] #23786
04/24/06 01:24 AM
04/24/06 01:24 AM
Joined: Jan 2005
Posts: 1,260
Las Vegas NV
moparmanjames Offline
pro stock
moparmanjames  Offline
pro stock

Joined: Jan 2005
Posts: 1,260
Las Vegas NV
So what brand of rings would you use in a bracket car NA making around 600 hp?

Re: Ring Gap [Re: moparmanjames] #23787
04/24/06 02:36 AM
04/24/06 02:36 AM

A
Anonymous OP
Unregistered
Anonymous OP
Unregistered
A



Quote:

So what brand of rings would you use in a bracket car NA making around 600 hp?




for a combo like that we would recommend your typical plasma moly ring set. some "brands" are actually made by the same company so i won't get in to the different brands here. some ARE better than others though IMO. the brands that we sell are the very same ones that we use day in and day out with great results.

Re: Ring Gap [Re: BradH] #23788
04/24/06 08:02 AM
04/24/06 08:02 AM
Joined: Jan 2003
Posts: 16,917
NC
440Jim Offline
I Live Here
440Jim  Offline
I Live Here

Joined: Jan 2003
Posts: 16,917
NC
Quote:


I still don't understand why it would behave any differently with a bigger 2nd gap than a same-size 2nd gap...


Well, the science of it may not be understood, but SpeedPro did some tests and the results are the bottom line. Does anyone have that link to the SpeedPro tests? Brad, perhaps check their web site.


1993 Daytona, 5.50 at 130mph (1/8) 1.19 sixty ft (PG). Link to 572 B1 - Part 1
Re: Ring Gap #23789
04/24/06 09:55 AM
04/24/06 09:55 AM
Joined: Jan 2005
Posts: 1,260
Las Vegas NV
moparmanjames Offline
pro stock
moparmanjames  Offline
pro stock

Joined: Jan 2005
Posts: 1,260
Las Vegas NV
"for a combo like that we would recommend your typical plasma moly ring set. some "brands" are actually made by the same company so i won't get in to the different brands here. some ARE better than others though IMO. the brands that we sell are the very same ones that we use day in and day out with great results."


Thanks, I was hoping that would be the case.
I recently did a budget build up and used Hastings Moly rings and they seem to work fine.

Here is the link to the Speed Pro Link:
http://www.federal-mogul.com/fmeconnect/technicalservices/downloads/1204.pdf

Re: Ring Gap [Re: moparmanjames] #23790
04/24/06 09:58 AM
04/24/06 09:58 AM
Joined: Jan 2003
Posts: 5,484
SoCal
Brian Hafliger Offline
master
Brian Hafliger  Offline
master

Joined: Jan 2003
Posts: 5,484
SoCal
Hastings are TOP NOTCH!

Re: Ring Gap [Re: Brian Hafliger] #23791
04/24/06 10:02 AM
04/24/06 10:02 AM
Joined: Jan 2005
Posts: 1,260
Las Vegas NV
moparmanjames Offline
pro stock
moparmanjames  Offline
pro stock

Joined: Jan 2005
Posts: 1,260
Las Vegas NV
Quote:

Hastings are TOP NOTCH!




Thanks, I didn't know that since they are inexpensive I was worried a bit.

Re: Ring Gap [Re: 440Jim] #23792
04/24/06 11:18 AM
04/24/06 11:18 AM
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
B
BradH Offline
Taking time off to work on my car
BradH  Offline
Taking time off to work on my car
B

Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
Quote:

Quote:


I still don't understand why it would behave any differently with a bigger 2nd gap than a same-size 2nd gap...


Well, the science of it may not be understood, but SpeedPro did some tests and the results are the bottom line. Does anyone have that link to the SpeedPro tests? Brad, perhaps check their web site.



The only tests I saw that SpeedPro described showed the effect of having too small a gap with the top ring. There weren't any that I found that compared tests with the second ring gap.

BTW, the one test did show that the tighter top ring gap made more power right up until the ring's ends started butting together, at which point you can guess the results.

BTW(2), nobody seems to have picked up on one of my previous comments, so I'll restate it:
Quote:

As long as the second gap is at least as big as the first, there shouldn't be any pressure build-up. If there is, then something else is going on that's not being taken into account by simple ring gap math comparisons, such as additional blow-by getting past the ring-to-cylinder contact area, in addition to what would be expected to get through the ring gap.



If that's the case, then you're simply making it wider for the undefined "what if?" scenario.

Last edited by Brad_Hawk; 04/24/06 11:45 AM.
Re: Ring Gap [Re: BradH] #23793
04/24/06 11:52 AM
04/24/06 11:52 AM
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY Offline
Master
MR_P_BODY  Offline
Master

Joined: Jun 2003
Posts: 52,972
Romeo MI
Also you have to see that the material of the rings
are different so it might be thermo/greater expansion

Re: Ring Gap [Re: BradH] #23794
04/24/06 12:02 PM
04/24/06 12:02 PM
Joined: Jan 2005
Posts: 1,260
Las Vegas NV
moparmanjames Offline
pro stock
moparmanjames  Offline
pro stock

Joined: Jan 2005
Posts: 1,260
Las Vegas NV
Quote:


The only tests I saw that SpeedPro described showed the effect of having too small a gap with the top ring. There weren't any that I found that compared tests with the second ring gap.

BTW, the one test did show that the tighter top ring gap made more power right up until the ring's ends started butting together, at which point you can guess the results.





I think what you have to visualize is that during high RPM cycling, pressures can build up between the rings over time. At just 6000 rpm, each cylinder is firing 50 times per second. Remember, during combustion you have a high pressure atmosphere in the cylinder to fill the gap between the rings much faster than it can escape through the gaps and equalize with the rapidly changing environment. So pressure builds up and tries to escape not only through the ring end gaps, but past the rings' seating surface. This pressure will want to take the path of least resistance, if the top ring has less tension, then it will unseat first.
Boy, good thing I slept at a Holiday Inn last night.

Re: Ring Gap [Re: MR_P_BODY] #23795
04/24/06 12:05 PM
04/24/06 12:05 PM
Joined: Feb 2003
Posts: 12,675
Columbia, CT
M
moper Offline
I Live Here
moper  Offline
I Live Here
M

Joined: Feb 2003
Posts: 12,675
Columbia, CT
Brad, I'm not sure if I can say it right..but.. If the first gap is just a hair large, becuase you file it for worst case, you will have a small amount of leakage. You also have leakage around ring lads, behind the ring, and a small amount between the wall and ring. Nothing is 100%. So, if a small amoutngets by the 1st ring, you want to make sure it can find an easier path out then by putting pressure up on a ring that isnt designed to seal against that. Think of a damn and a lake. The spillways are much larger than what they will noramlly ever need to pass, because if you were to have a deluge, and limited time for the floodgates to react, you have to be able to pass all out thru one spot..the spillway. In the rings' case, you have a small amount of time to release the pressure bled thru to the second ring. (the piston's upstroke) So you want to make sure there is enough room to get it out. The 2nd ring wil leak all the same ways the top did, but you cant have any pressure between them. So you leave a bigger hole for it to escape.


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.
Re: Ring Gap [Re: moparmanjames] #23796
04/24/06 12:16 PM
04/24/06 12:16 PM
Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
B
BradH Offline
Taking time off to work on my car
BradH  Offline
Taking time off to work on my car
B

Joined: Jan 2003
Posts: 15,439
Val-haul-ass... eventually
Quote:

...pressure builds up and tries to escape not only through the ring end gaps, but past the rings' seating surface...



Isn't this exactly what I've been suggesting / asking???

If the only top ring leakage is at the end gap, then there is no reason for the second ring gap to be any larger than the top ring gap (i.e., if the barn's front door only opens wide enough for one cow to go in, the back door only needs to be wide enough for one cow to go out to keep from having a traffic jam ). However, if there is any additional pressure getting past the top ring that isn't accounted for by the size of the end gap (farm analogy continued: a UFO lowers another cow into the barn through a hole in the barn's roof ), then the second gap would need to be wider (but by how much???) to to offset the potential for pressure build-up between the two rings.

BTW, why do we even bother having more than just a top ring with this approach? What benefit does the second ring provide if it's not there to trap the pressure that escapes the top ring? Plenty of motorcycles (2-stroke engines, mostly IIRC) only use one compression ring...

Page 2 of 4 1 2 3 4






Powered by UBB.threads™ PHP Forum Software 7.7.1