Ring gaping ?

I'm getting ready to gap my mahle rings.Doing a 355 NA (might run a 150 max shot now and then).I was looking at the spec sheet Top ring gap .018 NA (.0045x4.030) 2nd ring gap .022 NA (.0055x4.030) .If running 150 shot .024 top and .030 2nd.

1 what would be the gap tolerance +.002/-.000 ?
2 old school says smaller 2nd ring gap is this no longer true?Whats better?
3 .006 differance between NA and 150 nitrous,Might run small shot at the
track should I run the bigger gaps?How much will this hurt if I never run gas?
4 do the gaps look ok? Or should they be changed at all?
5 any advice you have to offer.
6 THANKS

How far down is your top ring? What width ring?

I'm getting ready to gap my mahle rings.Doing a 355 NA (might run a 150 max shot now and then).I was looking at the spec sheet Top ring gap .018 NA (.0045x4.030) 2nd ring gap .022 NA (.0055x4.030) .If running 150 shot .024 top and .030 2nd.

1 what would be the gap tolerance +.002/-.000 ?
2 old school says smaller 2nd ring gap is this no longer true?Whats better?
3 .006 differance between NA and 150 nitrous,Might run small shot at the
track should I run the bigger gaps?How much will this hurt if I never run gas?
4 do the gaps look ok? Or should they be changed at all?
5 any advice you have to offer.
6 THANKS

Yep larger 2nd ring gap. Put the gaps in there that the manufacture says and going too big on gaps is not a bad thing.

Bret

How far down is your top ring? What width ring?

top land is .093 Ring thickness is .058 x .149 width.

Bret I think what your saying is bigger is safer.On a leak down test how much of a loss do you think there would be between .018 top /.024 2nd vs .024 top /.030 2nd ?When you do gaps how do you balance out between running NA and maybe a shot of nitrous.I know we can't have every thing.

I'm in a similar situation, but going to run a small-medium boost blower on my 383, and I have Mahle pistons with the metric rings like you do. I called the tech at Mahle and discussed it and he said I should run a gap in between the NA and Blower gaps listed on that sheet that comes with the pistons. I haven't yet decided if I am going to do that or go larger.

With Nitrous, it might need to be gapped for worse case, cause when you're on the gas, it don't matter that you run around 99.9% of the time not on the gas.

How far down is your top ring? What width ring?

do you have a normal set of specs that you go by? like top ring

.150 down bore 5/16 ring gets .0xx gap
.250 down bore 5/16 ring gets .0xx gap
.300 down bore 5/16 ring gets .0xx gap

what do you usualy look for in an engine running a 150shot with his rings
Ring thickness is .058 x .149 width

Yep larger 2nd ring gap. Put the gaps in there that the manufacture says and going too big on gaps is not a bad thing.

Bret


why the larger 2nd gap now?

why the larger 2nd gap now?

Thinking on piston ring gaps has also changed. In the old days, second ring gap specs were tighter than those for top rings because they didn't see as much heat. But this didn't account for inter-ring gas pressure buildup between the top and second rings. If the pressure between these rings equals or exceeds the pressure above the top ring, it can cause the top ring to lift off the bottom of the piston ring groove and lose contact with the sealing surfaces. It also inhibits the ring's ability to transfer heat from the piston. To keep inter-ring pressure from becoming a problem, the current trend is to create an easy escape path for the built-up pressure by gapping the second ring larger than the top ring. Another benefit is that because gas pressure is now directed downward toward the sump, any oil that has collected in the ring pack areas will go with it.

ps this is copied from car carft

Ring gap is HUGLY affected by piston material and overall design. ALWAYS go by what the piston manufacturer says, not what the ring manufacturer says. You can thow all the old "rules of thumb" in the trash. They'll get you in more trouble these days than they'll help.

Too big a gap is always preferable to a gap that's too small- destroy a motor or two from butting the rings closed under detaonation (as I have several times) and you won't think going smaller is such a good idea. If you look at the actual exposed open area of a ring gap (piston-to-wall gap X ring gap), it's a pin-prick. Open it up from .025 to .030 and it's just a slightly larger pin prick.

listen to him!

FWIW I know a few guys who found more power with MORE ring gap and not less even though the rings were not butting together.

Bret

Thinking on piston ring gaps has also changed. In the old days, second ring gap specs were tighter than those for top rings because they didn't see as much heat. But this didn't account for inter-ring gas pressure buildup between the top and second rings. If the pressure between these rings equals or exceeds the pressure above the top ring, it can cause the top ring to lift off the bottom of the piston ring groove and lose contact with the sealing surfaces. It also inhibits the ring's ability to transfer heat from the piston. To keep inter-ring pressure from becoming a problem, the current trend is to create an easy escape path for the built-up pressure by gapping the second ring larger than the top ring. Another benefit is that because gas pressure is now directed downward toward the sump, any oil that has collected in the ring pack areas will go with it.

ps this is copied from car carft


Dam good explanation;)

do you have a normal set of specs that you go by? like top ring

.150 down bore 5/16 ring gets .0xx gap
.250 down bore 5/16 ring gets .0xx gap
.300 down bore 5/16 ring gets .0xx gap

what do you usualy look for in an engine running a 150shot with his rings
Ring thickness is .058 x .149 width


I generally go by the manufacturers recommendation.
I also don't run the ring "down" the piston like some do.Ya don't get a "clean" burn like that.
I have an engine know that is running a 300 shot with the rings .120 down where a N/A engine is.
I generally check their spects with mine
street build=.005 top x bore
.0055 2nd x bore
No2=.0065 top x bore
.007 2nd x bore.

Having said that my last two used gapless top ring and they seem to really work good. They are $300.00 a set and most people won't pay that much unless it's a trailer queen.
I also don't use narrow rings in a performance build.I use 1/16 x 1/16 x 3/16 with standard tension unless it's a trailer queen then I will use .043 top or run just 2 rings but that set up doesn't last long with just two rings.
If the compression get's past the top ring you're done anyway.

Piston MATERIAL affects ring gap as much as it's design, like I said above. Having done some research on this subject myself it appears that thermal conductivity of the piston material plays as much of a role in ring gap as the design of the piston does (how far down the top ring is from the face of the piston).

Coefficient of expansion of the material actually plays a very small role in all this, believe it or not. How the piston design/material manages heat is the real key.

Example:

Keith Black hypereutectic pistons have very low thermal conductivity. That's the biggest reason you can run tight piston to cylinder clearance, but also the reason they require MASSIVE top ring gaps. All the heat stays up on the top of the piston- from the top ring up- very little gets conducted down the body and into the skirts.

Keith Black forged pistons have a very high thermal conductivity. You have to run much larger piston to cylinder clearance becuase the whole piston gets hot and expands as the face of the piston heats up. However, this also helps conducts heat away from the top ring so you don't need to run a very large ring gap.

Going by Sealed Powers recommendation, I ended up with an .024" top gap, and .026" second gap. This is with Ross 4.030" bore nitrous pistons for my 355.

Frank

Thinking on piston ring gaps has also changed. In the old days, second ring gap specs were tighter than those for top rings because they didn't see as much heat. But this didn't account for inter-ring gas pressure buildup between the top and second rings. If the pressure between these rings equals or exceeds the pressure above the top ring, it can cause the top ring to lift off the bottom of the piston ring groove and lose contact with the sealing surfaces. It also inhibits the ring's ability to transfer heat from the piston. To keep inter-ring pressure from becoming a problem, the current trend is to create an easy escape path for the built-up pressure by gapping the second ring larger than the top ring.Nothing to do with heat anymore than it did 15 or 20 years ago. It is just a case of engineers getting smarter. If engineers (20 years ago), knew all there was to know, they would be unemployed today. This holds true with any race team engineers in service today as well. This is why race cars slowly get faster as time goes by. Any engineer that proclaims to have all the answers is either lying or not very smart. Cheating notwithstanding, the faster cars are not without engineering screwups, they just have fewer screwups. This is what progress is about. Enuf ranting.

This in not new ring technology. Look at your 10+ year old GM service manual. Some ring mfrs. have been recommending larger 2nd ring gaps longer than that.

Nothing to do with heat anymore than it did 15 or 20 years ago. It is just a case of engineers getting smarter. If engineers (20 years ago), knew all there was to know, they would be unemployed today. This holds true with any race team engineers in service today as well. This is why race cars slowly get faster as time goes by. Any engineer that proclaims to have all the answers is either lying or not very smart. Cheating notwithstanding, the faster cars are not without engineering screwups, they just have fewer screwups. This is what progress is about. Enuf ranting.

This in not new ring technology. Look at your 10+ year old GM service manual. Some ring mfrs. have been recommending larger 2nd ring gaps longer than that.


The engineers knew 10-15 yrs ago about rings.
They didn't have the material or machining practices or machines they do today.
Hell the piston makers JUST got machines to cut the lands flat within .0001--- Didn't have that 10 yrs ago.
There are also different ring materials today.
Most of the improvements are material and machining.

The engineers knew 10-15 yrs ago about rings.
They didn't have the material or machining practices or machines they do today.I can agree to the time frame noted above. However, I don't believe advancements in materials or machining had any bearing on change to 2nd ring having the larger gap. The evidence being that the larger gap was incorporated at that time. This is the advancement in knowledge (getting smarter) I was referring to. There are also different ring materials today.
Most of the improvements are material and machining.I agree this can apply aptly to your reference to the gapless ring. It took improvements in material to allow the gapless to survive in the high heat region of the top ring land. This is where that ring belongs BTW. AFAIC, the gapless 2nd ring engineers were aware of this larger 2nd technology when they released their product. So why did they regress in their work by defying that technology? I could see some gain with the gapless 2nd ring, but obvious negatives were apparent. Overall, was it really a plus? Was it marketing to by some time? The negatives were negated by finally being able to bump the ring up into the top groove. Another rant? :) Anyway, thanks for your reply racer.

I can agree to the time frame noted above. However, I don't believe advancements in materials or machining had any bearing on change to 2nd ring having the larger gap. The evidence being that the larger gap was incorporated at that time. This is the advancement in knowledge (getting smarter) I was referring to. I agree this can apply aptly to your reference to the gapless ring. It took improvements in material to allow the gapless to survive in the high heat region of the top ring land. This is where that ring belongs BTW. AFAIC, the gapless 2nd ring engineers were aware of this larger 2nd technology when they released their product. So why did they regress in their work by defying that technology? I could see some gain with the gap less 2nd ring, but obvious negatives were apparent. Overall, was it really a plus? Was it marketing to by some time? The negatives were negated by finally being able to bump the ring up into the top groove. Another rant? :) Anyway, thanks for your reply racer.


I have run both the gap less 2nd and top and they both did fine. They still sell both and the gap less second shoots the larger gap second theory all to hell.
My contention has always been that if compression gets past the top ring ya are done anyway.
I like the gap less top just from the statement above.
On the top and second ya run the gap as close as ya can without butting the ring.This takes experimenting and most don't do it. Ya got to run a gap and try it in YOUR situation and keep tightening until ya get them touching and back off or run out of daring.A trailer queen can stand closer gap than a driver. There is more power to be made with NO gap if possible.
If ya can tear an engine down and there are no or very little black deposits below the top ring ya got it right.

Sales pitch????

Larry.... I've seen some results where you back the gap off, WAY OFF from touching and it made more power... so who knows if that even holds true anymore.

Bret

I believe this is in step with the larger gapped 2nd ring reasoning. Once it gets passed the 1st ring, main concern at that point is to just get rid of it as efficiently at possible before it does more damage
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Can't see that. It's not suppose to get past the top ring.That's why the got gapless top ring to try to prevent it going in the base


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One main (1st) ring for compression, one for oil, and if a third (2nd groove) is used, to aid oil control more than anything.I used to agree with that, but along with that noted above in other posts, there have been documented accounts of increased HP/torque after engine assembly with rings gapped way to large unintentionally.[/QUOTE]

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Going to have to show me that it was the ring gap that did it.
There is a possibility that the gap was too small and butting the rings lightly. That unseals the one that was touching.
Either way ya can't make HP with a base full of compression and it's hard to keep oil in it.
Let's say ya got .030 gap in the top ring,what's to say that when the engine is running in it's given water temp range and combustion temp range that that's two large.Ya can't rattle one and expect the gap not to close up. It may only have .001 gap while running in it's intended atmosphere. So where do ya draw the line as being "too large". Without experimenting ya don't know,ya just have a general idea.
The manufactures spect is a spect to cover most all situations.
Don't tell me about the EM either,that's an experiment in surviving detonation.

Don't tell me about the EM either,that's an experiment in surviving detonation.

It was!

10.5:1 mandated now....

My guess is it's partly to do with the junk gas. Other part has to do with making them relatable to the masses.

BTW oldDUDE here is some reading for ya

http://speedtalk.com/forum/viewtopic.php?t=152

Bret

It was!

10.5:1 mandated now....

My guess is it's partly to do with the junk gas. Other part has to do with making them relatable to the masses.

BTW oldDUDE here is some reading for ya

http://speedtalk.com/forum/viewtopic.php?t=152

Bret


"I have a customer that has gone through his 540 Chev many times due to his dis-satisfaction with ring seal. He has the time & financial freedom to do all he needs to accomplish these goals. So that allowed him to gain information from many sorces. ------ Using the std rings available from different vendors, he went through pistons as well to run this down. ----- What he found when all was finished and re-learned, it was found the Total Seal gappless top ring was head & shoulders above the non Total Seal. --- The key was the wall finish. Nothing like what is being used with conventional rings. The power level was up notabley & ring seal was just like they claimed. The second issue was the break in. He found the ring had to be set not on a power up cycle on the dyno, (chassis) but a high vacum coast down using the energy from the drive. There was abnormal oil smoke produced wich progressed out after a number of pulls. Only then did the engine seal properly. ------ It seems the ring does infact show a positive when you look at things differently. He spent an awfull lot of money, but most of all, the open mind won out."

Here is a guy that makes sence to me.
I have used both the gapless rings and they work good. I also got my machine shop to talk to Total Seal about the cyl wall finish and they got the needed stuff.Sooooo it will work if ya got the right stuff. Been there.

Yeah the dry install with quick seat and the right cylinder wall finish is the key.... most people cant do that. Hell I've never done a set of rings WITH oil on them! Shows my age.

Yeah the dry install with quick seat and the right cylinder wall finish is the key.... most people cant do that. Hell I've never done a set of rings WITH oil on them! Shows my age.

Yea, since the R&D with C&A I have learned to soak a rag with 30W and wring it out and run it in the cyls. I have a squeeze bottle that I oil the pin with and use the rag on the skirt and sock it to it.
The first time I did that I expected the rings to be ALL broke up and molly all in the pan after the around the block break in. Well it stopped smoking before it left the shop and when torn down the rings were worn out but the walls were ready for a new set.