DavidNJ

Most of the shelf LS1 pistons seem to have the 1.5mm/1.5mm/3.0mm ring package with the top ring down over .2". This is the description from Diamond:

What would be the optimal ring size, top land, spacing, tension, finish, and gas porting, if any, for a serious street/strip/track day effort.

Thanks,

David

racer7088

David,

There no exact answer to that question because the ring pack changes with the application totally. What Diamond has laid out there is very good though with lower tension rings and a nice strong top land of .250 thickness. You could go thicker for crazy power adders but it's a nice overall setup.

There very good reason for all the different rings that are offered and the different spacings but it's too complicated to go into at length on a board like this.

gun5l1ng3r

Well, this is the advanced board, and one of the most advanced boards I have come across. Could you point me in the direction where advanced topics are discussed in more depth than here? I am very interested in learning as much as I can on how the internal combustion motor works and how to maximize performance.

Thanks,
Jake

DavidNJ

The few books that talk about do it in 1-2 pages...however they are all pretty old (20 years or so!).

Here are some examples of the issues. The .250 top land is spec'd for 'light nitrous', yet the blower piston (upto 25psi) is only .050 bigger. The older design had .210". Many other pistons have under .200" Why not use a .150 or .100 top land?

A 1.5mm ring is .059. A 1/16 is .0625, only 6% thicker. Why not use the readily available 1.2mm (.047") or even more available .043 rings? What about a Dykes ring, or are these just relics of the past?

3mm is already a small oil ring at .12". Does it provide a benefit or detriment against a 1.88" 3/16" ring. Isn't just the ring tension we are interested in?

Does the Napier second ring provide an advantage in sealing and oil control?(picture from JE ring catalog)


How important are issues of microwelding, surface finish, and flatness? (picture from JE ring catalog)


These are some of the JE piston options:

LOnSLO

iTrader: (15)

FWIW, I use a light tension .043 top ring, Napier .043 second, and ultra low tension 3.0mm oil rings. I think it is the optimal optimal ring package for my combo. As Erik said above, every combo will be different. Just to add, there is an infinite number of ring combinations, and custom ring sizes, so it's basically application specific.

DavidNJ

Is the top ring backcut? What are the land heights? Is the piston gas ported? What is the oil ring tension? Lots of questions beyond .043/.043/3mm.

LOnSLO

iTrader: (15)

Yes, top ring is backcut. Can't remember exactly to what though, I don't have them in front of me. Piston is vertical gas ported. Oil ring tension is between 5 and 8 lbs.

LOnSLO

iTrader: (15)

Also, check out Total Seal's catalog to see what's out there.

racer7088

I agree but Davids first question was too open ended kinda like the what cam should I buy threads.

I think this could be a good thread and I will try and get some real experts in here if possible.

Smaller rings are more conformable and lighter so they are easier to control at higher engine speeds and seal up a little bit better usually.

The rings are a seperate but related subject and the piston and it's design and cinstruction is another for sure including ring land locations etc.

racer7088

David,

The main difference in the 1/16 and 1.5 mm vs the very small rings is life in a real car. Some of the race rings won't last as long or work in as bad a conditions as the stock ring size but rings are getting smaller and thinner every year. Other than that smaller and lighter is probably better since it makes rings seal better and float or flutter less.

You can use a thinner top land if you aren't making any power but too thin and you will burn it and the ring will see too much heat too on some apps. Many stock cars like the LS1 etc. have a top land of around .170-190 and they are cast pistons but again made for emissions and NA only usage.

The oil rails again use tension and conformability to scrape oil so you can use less tension if you don't have as much oil flying around in an engine or if the rails are much more conformable. Otherwise you need good old fashioned radial tension to scrape the oil away. The napier seconds are another upgrade and scrape oil very effectively. They will only be used more and more I think as time marches on.

Most gas ported pistons are made with slightly tighter ring lands and better quality rings so they will flutter less at high rpm and seal better with more gas pressure on them but yet release while not under the power stroke. If you just gas port a piston that has regular rings it might seal little better but it also may wear out faster too.

With the right vacuum pump or dry sump system you can run much lower overall ring tensions and get some free power and yet still not oil the cylinders. If you do all this stuff and don't know what you are doing you will have a smoking pig on your hands though, this stuff is usually NOT for the street with a normal engine that is idling at high vacuum all the time without any crankcase vacuum.

DavidNJ

That is a good point. How low a tension can be used on the oil ring? And that still would allow .043 top and second rings.

Some people say gas porting consumes the rings and the walls too quickly for the street. Others say they have no problem. Of course, the people who say there is a problem have minimal if any experience using gas porting on the street.

There is another whole question about ring flatness and surface finish. Apparently the flatter, smoother rings can use flatter, smoother ring grooves with less axial clearance. Apparently gaining less flutter and better sealing.

There are also coatings for the ring grooves, although I am not sure which one.

The questions are about what works; when and why. With real life examples if possible.

So much of the discussion on LS1Tech is about CFM, not about friction, sealing, and combustion. But these are also important. If you can slap a head/cam/intake/headers on an LS1 and get 460rwhp, I'm pretty sure taking care of the sealing, friction, and maybe some thermal management from reduced bearing sizes, clearances, coatings, oil pump pressure, oil pump size/volume, and ring tension and improved sealing could be enough to push you toward 500.

gametech

iTrader: (1)

I would love to hear someone who is knowledgable about ring material, not just size and tension, chime in hear. That is yet another variable that can be different depending on application.

racer7088

All good point except about the gas porting. There's a reason none of the oems does this for long term street use. Why would you say people that think it wears rings out faster don't have experience with gas-ported rings on the street? I can tell you first hand that most of the clowns I see doing stuff like this have had some big problems and also usually have smokers. Theres people that are reading this that know what I am talking about. Maybe that was a misprint. People have been gas porting amd MIS gas porting for years.

Rings already have clearance on top for the gas to activate them and if you are already running normal radial tension rings and full size ring grooves AND adding multiple gas ports you ARE gonna have more wear. Anyone that doesn't understand this needs to go to the junkyard and see where all cylinder wear is. It's there at the top for a reason and that where gas pressure is highest on the rings pressing them into the cylinder walls and then you go and add even more ring to wall pressure and your going to have more wear. It's not something that people think might add more wear. It does add more wear.

Whether or not this will add too much more wear or not is up to the user but if you are using regular rings like this and they really need gas ports it also means you probably have other problems. Again I am not talking about correctly designed back cut rings in grooves that are tighter where there might not be sufficient radial pressure from the limited gas that would activate them as they NEED the gas ports and are designed with this in mind. These types of pistons though with gas ports will clog up over time on a regular carboned up idling street car however that runs with vauum above the pistons and pressure below it most of the time(the opposite of a race car which is what these back cut gas ported rings are really made for).

racer7088

There's tons of rings for the top and the second and the oil ring. The all do seperate jobs with some overlap.

The top of course sees big heat and pressure and must seal off combustin pressure by sealing down against the second ring land and out against the round cylinder walls.These are usually ductile cast iron with a Moly filling that the ring rides on and is a barrel faced (rounded) and smooth edge that rides against the cylinder and seals the pressure above the piston. Extreme power adder rings are made of even steels taht are coated and also usually barrel faced.

The second is mostly an oil scraper and a semi compression ring but not much normally! These are usually grey cast iron or ductil cast iron and are downward facing sharp edged rings that scrape oil downward only. There are even steel second rings too and some are even teh taperd hook groove or napier style like in David's picture above. Napiers are super efficient oil scrapers.

The oil ring is of course responsible for scaping the lion's share of the oil off the cylinder walls. The better ones are more conformable and can scrape more oil off with less radial tension and friction as a byproduct. These oil rings are usually steel and the scraper rails are also usually chromed so their narrow edges last longer. There are oil rails right now down at 1.5mm and some one-piece oil rings too but that stuff is still a little farther off in eth near future.

ALL of these rings require appropriate hone jobs as well to work the best which is a whole nother story.

nytoy

iTrader: (3)

Can someone reccomend an oversized 3.905 sized piston and ring package for a stock LS1 block that's getting overbored?

Use will be street / road racing. Mild Head and cam car. For a year it will be a cam only car. Had serious issues with engine braking/decell burning oil, so I'm especially interested in some super nice oil scraper rings.

DavidNJ

Erik, I thought one of the main advantages of gas porting was to use back cut rings (say .140) to reduce friction on three of the four strokes and reduced flutter from reduced axial clearance. I didn’t think gas porting was as effective if the rings were the standard depth (.170-.180) or if there was significant axial clearance.

I have talked with 6-8 engine builders on the phone. Some say there is excessive wear on the rings and cylinder bore, possibly requiring rebuilds after as little as 2k miles. The builders who reported it didn’t work generally didn’t continue building gas ported engines for the street. As a result, they had limited personal experience. However, two builders (who I consider quite reputable) have told me that they do it without a problem. One told me that he has gotten 30-50k miles on a street driven gas ported engine.

Is the problem with the street driven gas ported engine primarily oil entering the combustion chamber from high idle vacuum and high crankcase pressures? Does using a dry sump or vacuum pump mitigate this? Is this still a problem if synthetic oils are used? Does using a Total Seal gapless top ring reduce the problem?

Have you built gas-ported engines for street use? If so, did they have problems? What rings and clearances were used? What oil was used? How was the crankcase pressure controlled?

Thanks,

David

racer7088

David,

That is the reason we use race rings in the first place and many of course are gas ported.

When I am ranting I am talking about regular pistons with regular full tension non-backcut rings getting gas ports and sometimes plenty of them! People doing this are not always the sharpest pencil on the table.

The problem IS the difference in crankcase vs cylinder pressure when using low tension rings plus the LS1 slings tons of oil around with it's crappy drainback and huge lifter clearances when hot.

I've done some gas ported stuff for the street that worked fine but had higher tension oil rings and better 2nd rings as well. The guys didn't care if they replaced the rings every once in a while since they were hard core street racers.

DavidNJ

Since the LS1 overlaps the SBC in bore size, there are tons of ring sets available. The big cost would not be the rings, but the custom pistons to use them.

How long a service life did your customer get with backcut, tight clearance, gas ported rings?

Are you saying you would use something like a Total Seal Gold Finish with .043 x .140 top ring, gapless, .043x.140 Napier second ring, and 3mm third ring? If so, would you order something like the JE Ultragroove to hold the top rings? And what size ring grooves and how many lateral gas ports would you order?

If you using a set like that, would you replace the 9-12# oil ring with an 18-22# one? If so, how much friction does it add?

Thanks,

David

Is there anything you can do to an LS1 to improve the oiling? Would a 4 stage (with one lifter valley scavenge) be the solution?

If running NA, would you push the top ring up to .150 or .100? How would you space the other lands? Would you use an accumulator groove on the second land? Would you add contact reduction grooves to the top land?

LOnSLO

iTrader: (15)

Just FWIW, the Gold series rings are very nice. Have used them before in a .043, .043, 3.0mm set. 5 stage dry sump would be the best as far as oiling system goes. You can use the 4th scavenge line on the valley cover.

DavidNJ

I've only seen on LS1 dry sump setup that allows you to keep the A/C. An expensive Australian one. Most (all) LS1/2/6/7/92 equiped street cars would seem to have mounting issues for the tank.