Anyone here running the small compression rings (.043) for a BBC? If so, what are the pros/cons? Any power increase? What's the application? How is the longevity? Are you using a scavenging vacuum, mechanical crank vacuum? Gas ports in the pistons? What piston/ring manufacturers? Thanks in advance for any practical information you may offer. I'm thinking about using these on my rebuild.

Kind of strange you posted this Ken.

I too am interested in hearing any input. Been looking the past couple days at ring packages and any power gains possible with them.

Do your pistons have the small .043" rings, or are you replacing your pistons? The JE/SRP's & Ross pistons I'm looking at using both use 1/16", 1/16", & 3/16" rings grooves (both basic off the shelf pistons).

I am more than likely gonna do some sort of low tension ring set, especially since I already run a vacuum pump setup.

I've read a little about radial back cut compresion rings which offer lower drag. Have not gotten any solid data on input as of yet. Early in the search process.

Look forward to hearing what some of the input is on this subject. Did you read the article on Reher Morrison's site on rings under the tech section?

I am probably also gonna have these pistons dry film friction reducing coated on the skirts and the domes thermal coated. The previous lil rat had the pistons coated and I feel that may have been part of the reason it ran so well for it's small size. It takes a bunch of little power gaining tricks here and there to add up to measurable power gains in the end. Just have to sort through the ones that do work, the ones that may work, and the ones that work, but put your engine at potential rick of damage or failure.

You doing a standard of high volume oil pump this time?

Hi Todd,

No, my pistons are 1/16", 1/16". They are on Ebay right now. I had been planning to reuse them as the block only needs a hone to clean it up. However, the rods were pressed on at .005 interference and won't come off without damaging/destroying the pistons. I had already bought new rods as I'm trying to reduce the rotating/reciprocating weight on the engine. I was previously running GM dimple rods which are a little on the heavy side. Long story short, I'm now in the market for a new set of pistons. I was going to order a new set based on the final honing measurement of the block to get the piston to bore clearance right. I thought if I'm going to order custom pistons I might as well look into some of the advances made in this area in the last few years. I don't like the idea of running a vacuum pump. I know they make more power but at the expense of shortened parts life. I'm going to see if I could just get away with a gas ported piston and an exhaust scanvenger smile.gif

Hey Ken,

Stumbled onto this site...

http://speedtalk.com/forum/viewforum.php?f=1&sid=9d6fccdd5e83fb8910d8c310d5384781

Worth using their search function.

What rods did you go with? What length and what is their weight?

I'm leaning towards the Eagle ESP 3D H-beam in the 6.385 length with the L19 bolt upgrade. I believe there 785 grams in weight IIRC.

Ken/Todd,

I was talking to my machinest about this subject the other day as well. According to him, there is definitely power to be found with the .043" ring package, but gas porting is required to get them to seal as they don't have the necessary tension on their own to seal. A vacuum pump is not absolutely required, but worth some power.

Todd, thanks to your link I have been turned on to SpeedTalk - hours of good reading there.

Thomas

.043" compression rings, when combined with 3.0mm oil ring assembly will make the ring package more compact, allowing the use of longer rods. There is a very small power increase in race-only applications when the radial thickness is reduced on the compression rings.

Most domestic engines utilize SAE specification classed as a 'D' wall. 'D' wall means that the bore diameter is divided by 22, therefore a stock BBC compression ring will have a radial thickness of .195" to .210". When the lateral thickness is reduced to .043" and radial thickness is down to .170, the result is a ring with much less tension. Less tension results in less friction and horsepower does increase. Gas porting is recommended with .043" top ring, especially with the reduced radial (aka "back-cut") format. Gas porting however does not work well with any engine driven on the street and should be left to race-only applications.

Vaccum pump should be used with and low tension OIL RING assembly, with a tension of 10 lbs or less. Exhaust scavange system (only effective with open headers), should be used with any oil ring assembly with less than about 13 lbs. Some NEXTEL Cup teams are now using 2.0mm oil rings with tension down to about 4 lbs.

EDIT - In my opinion the 1/16", 1/16", 3/16" ring package with ductile moly top, reverse twist tapered grey iron second and standard tension oil assembly is still the best combination for any street or dual-purpose, street/strip application.

Thanks for the input EngineGuy. After researching this issue I've decided to stay away from the low tension ring sets. I'm more interested in durability as I plan on running my engine atleast two seasons between rebuilds. I think that the low tension ring sets are good for class racers or other's interested in max performance and with more frequent service intervals. Many posts I've read from people using the .043 ring sets indicate that the rings are only good for ~125 passes. I'll be making 200+ passes a year so that simply won't work for me.

Thanks for all the feedback.

Ken.....saw your question......I run low tension oil rings in my pee shooter :D

Ken, i run the low tension ring set in my 383. the only down side i can see is the smoke just a tad. i did a leak down on the engine and am at only 2% leak down. was told they were only a 10k mile ring Dave