Are thin piston rings worth horsepower?

BILL-C · Post by **BILL-C** » Sat Feb 23, 2019 1:47 pm

We are doing some repair work on a stock 2017 benz 550 sl v-8 engine now. Stock ring package is 1.2mm steel top ring, 1.5 mm napier 2nd ring and 2mm oil ring. Compression ring grooves are hard anodized. Rods are piston guided.Hypereutectic Pistons are a box design with spherical dishes. This is totally stock. We also have a K 24 honda here that has a 1.2 , 1.2 , 2.0 ring package stock. 5/64, 5/64, 3/16 and even 1/16, 1/16, 3/16 rings are closer to model A technology than current engines. The new, light rings help in every way and at all rpm.

PackardV8 · Post by **PackardV8** » Sat Feb 23, 2019 2:03 pm

camaro/holland wrote: ↑Sat Feb 23, 2019 1:17 pm Have been looking at this for some time, so interested in your opinion about using thin rings on pistons with a standard ring groove and a spacer. Will you have the same gains, any drawbacks to going this way? Thanks.

Yes, No, Maybe.

A selling point for current pistons is the more precise control of ring groove dimensions. Introducing a second variable of a spacer obviously makes it more difficult to control total side clearance.

It will be interesting to see what the Super Stock guys have to say on this; they've been doing exactly this for some years now.

Also be interesting to see what others have been paying for spacers. We had an obsolete engine build for which OEM 3/16" dimension rings were not available. The spacer prices we were quoted by Hastings and Total Seal made it more cost-effective to use two sets of 3/32" rings in each groove.

jack vines

groberts101 · Post by **groberts101** » Sat Feb 23, 2019 2:05 pm

BILL-C wrote: ↑Sat Feb 23, 2019 1:47 pm We are doing some repair work on a stock 2017 benz 550 sl v-8 engine now. Stock ring package is 1.2mm steel top ring, 1.5 mm napier 2nd ring and 2mm oil ring. Compression ring grooves are hard anodized. Rods are piston guided.Hypereutectic Pistons are a box design with spherical dishes. This is totally stock. We also have a K 24 honda here that has a 1.2 , 1.2 , 2.0 ring package stock. 5/64, 5/64, 3/16 and even 1/16, 1/16, 3/16 rings are closer to model A technology than current engines. The new, light rings help in every way and at all rpm.

Yep, all that and better bore conformation is often worth something on the older iron too. Plus thinner rings allow more piston material above top ring for added durability or enables pushing ring locations even higher when build geometry is being pushed towards the outer limits.

Newold1 · Post by **Newold1** » Sat Feb 23, 2019 5:36 pm

Doctor says "Stay on the Diet, Go Thin!"

ProPower engines · Post by **ProPower engines** » Sat Feb 23, 2019 7:15 pm

travis wrote: ↑Sat Feb 23, 2019 5:04 am For an under 6500 rpm street engine with a carb, would the thinner ring pack have a shorter life expectancy? Many machine shops I have spoken with seem to think so.

Time to find better shops that do this kind of work and get real time results.

The OEM.s use 1mm to 1.5 mm ring packs and they get 250K out of them. Or more no problems there.
It is based on the bore finish and the material the top and 2nd rings are made from.
They are all using steel top rings at this point so long life is possible with the higher cyl. temps of todays new cars.

MadBill · Post by **MadBill** » Sat Feb 23, 2019 7:40 pm

The ring/bore contact force is mostly dictated by cylinder pressure. The narrow ring will be subject to less force but will have the same contact pressure regardless of ring width, so wear should be no different.

Re ring spacers, Total Seal offers notched ones that mimic lateral gas ports...

Post by **GARY C** » Sat Feb 23, 2019 8:14 pm

MadBill wrote: ↑Sat Feb 23, 2019 7:40 pm The ring/bore contact force is mostly dictated by cylinder pressure. The narrow ring will be subject to less force but will have the same contact pressure regardless of ring width, so wear should be no different.

Re ring spacers, Total Seal offers notched ones that mimic lateral gas ports...

But that only happens on the compression stroke so on intake and exhaust stroke wouldn't a lower pressure ring wear the bore less?

PackardV8 · Post by **PackardV8** » Sat Feb 23, 2019 8:22 pm

MadBill wrote: ↑Sat Feb 23, 2019 7:40 pmRe ring spacers, Total Seal offers notched ones that mimic lateral gas ports...

Yes, they do, but any time I've asked Total Seal about their spacers, the costs seemed way high. I had a perfect set of pistons with wider ring grooves. It was more cost effective to sell the existing pistons to a customer and get new custom pistons with the correct ring grooves than to buy Total Seal rings and spacers for the pistons I had. What am I missing there?

jack vines

MadBill · Post by **MadBill** » Sat Feb 23, 2019 8:24 pm

Maybe..

(Speaking to the Gary C post.)

tenxal · Post by **tenxal** » Sat Feb 23, 2019 8:59 pm

PackardV8 wrote: ↑Sat Feb 23, 2019 2:03 pmIt will be interesting to see what the Super Stock guys have to say on this; they've been doing exactly this for some years now.jack vines

The Stock and Super Stock stuff has been going this way for some time, now. A nice ring set is the Total Seal .9 mm setup. You get most all the goody of the .8 mm Diamond lapped setup at lower cost and more importantly, without the unknowns of bore prep that the Diamond lapped rings require. Not all race machine shops are comfortable abandoning their tried and trued ways of bore finishing and going to a totally Ra driven finish.

Most of the cylinder drag is oil ring related. This has gotten a bit more complicated since the demise of the SS50U oil ring expanders.

Gas ported spacers in 5/64" grooves aren't the easy fix, either. To do it correctly, the pistons need to be cut for that combo...just plopping the spacer/thin ring setup in grooves that were done for a 5/64" deal (even grooves done with the .135-.165 back cut in mind) will give you problems.

Post by **GARY C** » Sat Feb 23, 2019 9:04 pm

You just need something like this to cut down the outer edge of thicker rings.

1972ho · Post by **1972ho** » Sat Feb 23, 2019 9:14 pm

The only reason some stocker racer use spacers is we have to use the stock piston ring groove,I’m sure if it wasn’t for the rule everyone would just buy pistons with thin grooves from the get go.

digger · Post by **digger** » Sun Feb 24, 2019 12:00 am

tenxal wrote: ↑Sat Feb 23, 2019 8:59 pm Most of the cylinder drag is oil ring related. This has gotten a bit more complicated since the demise of the SS50U oil ring expanders.

this is really only true on a motored engine, on a fired engine the evidence suggests the top ring is causing just as many losses due to the gas pressure driving the ring harder into the bore

MadBill · Post by **MadBill** » Sun Feb 24, 2019 12:11 am

I wonder how they would quantify that?

camaro/holland · Post by **camaro/holland** » Sun Feb 24, 2019 2:08 am

tenxal wrote: ↑Sat Feb 23, 2019 8:59 pm Gas ported spacers in 5/64" grooves aren't the easy fix, either. To do it correctly, the pistons need to be cut for that combo...just plopping the spacer/thin ring setup in grooves that were done for a 5/64" deal (even grooves done with the .135-.165 back cut in mind) will give you problems.

Willing to elaborate?

Don Terrill’s Speed-Talk

Are thin piston rings worth horsepower?

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