Comparison of rings

[rmaynard 14,906]

I am in the process of rebuilding a K241S. I had the cylinder bored and honed and matched to the new +.020 piston.

Here is where my curiosity is piqued. The rings that came with the piston have the following end gaps:

Top: .012

Middle: .022

Oil: .028

These rings are of the design that have an inside bevel on the top ring, a bottom outside notch on the middle ring, and a one-piece slotted oil ring.

After contacting the supplier about the gaps, they sent me another set of rings, from the same manufacturer, but they were different in appearance and style. The top ring has an inside bevel, the middle ring has an inside bevel, and the oil ring is a three-part system.

Ring end gaps on these are as follows:

Top: .025 (corrected)

Middle: .025 (corrected)

Oil: .028 & .031 with wavy spring-type middle section

I know that Kohler specifies that end gaps for all rings be .010/.020 for new with a maximum of .030 for worn.

I am curious as to what the rest of you more knowledgeable engine rebuilders have experienced with ring styles and end gaps.

Why are some oil rings 3-part and others slotted? Why are some top compression rings made with one bevel and others with two? Why do some of the middle compression rings have a top bevel and others have a bottom outside notch.

Inquiring minds need to know.

Edit: I corrected the gaps on the 2nd set of rings after having them checked by the machine shop.

[iicap 1]

Bob, I CAN'T give you an authoritve answer about end gaps and different styles. I'm going to say the material they are made of may have something to do with expansion at operating temps. Because you asked about rings, I want to share something about Chrome plated compression rings. We had a lot of Perkins Diesel powered fork lifts where I worked for 30 yrs. all purchased new. These engines could have had chrome compression rings or chrome cyl sleeves but not both. When new these engines had noticable blowby and would use oil. Upon complaining to the dealer we were told that the chrome faced rings took a very long time to seat. It took somewhere between 800-1000 hrs and all visable blowby and oil consumption would be gone. The reason I mention chrome faced rings is that I believe I've read here on RS about them while rebuilding a Kohler. Although not what you asked, I thought it might fit in here.

[tommy3horse 3]

Bob;

When I have a Kohler engine bored, I give the machine shop the serial# and Spec# and thru Kohler, they order what is needed. Always Kohler for me, and that makes my job easier knowing that I have the exact part the manufacturer suggests.

I have rebuilt 4 engines is the past 2 years, 2 K301's, a K321 and finishing the K341 now and have never experienced inconsistency with correct Kohler parts, was this ring set an "off-brand" set?

Tom

:thumbs:

[rmaynard 14,906]

...was this ring set an "off-brand" set?

Yes, it is an off-brand.

[KB9LOR 4]

Bob that is not good, has anyone measured a genuine Kohler set of rings? I would be interested to know the specs the Kohler rings have.

[tommy3horse 3]

Brian,

I have the new set of Kohler rings for my K341 in hand, and I will let you all know when I can get into the icy garage to fit them.

Tom

:thumbs:

[Indy w h 4]

...was this ring set an "off-brand" set?

Yes, it is an off-brand.

Ya get what you pay for

Indy

[KB9LOR 4]

Brian,

I have the new set of Kohler rings for my K341 in hand, and I will let you all know when I can get into the icy garage to fit them.

Tom

Thanks Tom, I would like to see what the Factory specs on those rings in the cylinder compared to the aftermarket.

[sorekiwi 761]

Bob, Hastings has a lot of interesting ring information in the "Tech tips" area of their site. http://www.hastingsmfg.com/ContentData.aspx?Contentid=82

[rmaynard 14,906]

Thanks for the replies. All interesting. I am going to go back to the machine shop and have the bore remeasured just out of curiosity. Could be that my +.020 bore, which should measure out at 3.271, just might be a little bigger than it should, which would make all of the ring gaps too wide.

[rmaynard 14,906]

Just returned from the machine shop. The verdict is 3.271. Right on the money for a .020 bore. So, now the question is, are the aftermarket rings cut with too large of an end gap? Well, that appears to be the case. But why? Both sets, albeit different styles, have larger than specified gaps.

According to the information provided in the Hasting website (thanks to Mike), the ring gap should be no less than .0035 x the inside diameter of the bore. So .0035 x 3.271 = .0114 which is well within the Kohler specs of .010/.020. The maximum gap according to Hastings is what has been established by SAE, which in this case is .020.

Will genuine Kohler rings be any different? I guess the jury is still out on that since I don't have a set of those to check. Maybe we will find out when tommy3horse gets out to his garage.

[SkyhawkTL 19]

Just my two cents.....

We would rebuild performance engines when we reached 3% blowby - roughly 3 hours running. The valve seal would constantly degrade while the ring seal improved so the HP stayed the same. Ring development during this time even even allowed no crosshatch, with smooth cylinder bores - the moly ring made the adjustment. My point is that ring science is constantly changing and improving.

There are many excellent aftermarket parts that perform great when installed per the instructions. The "Best" parts are tough to call. Your engine work sounds solid and on the money. I'd feel good staying on your course.

Oh - and the Hasting website was excellent - Thanks Sorekiwi :thumbs:

[VinsRJ 721]

Stagger the rings correctly and you should be fine. If it was bored to the piston there should be no issues with slap and blow by will be minimal, if even measurable.

[sorekiwi 761]

Another though occurred to me while I was reading this.

Possibly the numbers given by Hastings as a guideline are based on watercooled engines which tend to run at a more constant temperature than an air colled engine? I dont think I've ever heard any mention of that before, but it may be something to take into consideration.

This is one of my all time favorite tractor threads (and I've linked to it a hundred times on various subjects!!) http://www.mytractorforum.com/showthread.p...nerable&page=14

(Its well worth a read if you have a spare hour or so to read through 19 pages of threads!!). On page 14, Volfandt (who is a member here) states that his Stens rings had a gap of .017" as opposed to .015 for a genuine Kohler set.

Seems to me that as long as the gap is within Kohler tolerance, that it will work OK. And end gap a few thou big is definately a lot better than a few thou too small...

[rmaynard 14,906]

Seems to me that as long as the gap is within Kohler tolerance, that it will work OK. And end gap a few thou big is definately a lot better than a few thou too small...

Mike,

That is interesting reading. At least page 14.

You are right with your last statement, and I would be very happy with .017 as a gap. But only one ring out of six is within specs.

My supplier is very cooperative and is waiting for a response from his source as to why the rings have such a wide gap.

Since I know that the bore is correctly sized, and the piston and rod can be installed later, I am going ahead with the re-assembly of all the other internal parts.

[tommy3horse 3]

Hello Bob;

I had the opportunity to fit the Kohler rings today. The end gaps are right at .017.

I am pleased with this fit. Kohler recommends .010 to .020. My bore has no taper and .002 wear and its round too.

On the buzz-kill, my supplier said that genuine Kohler parts took a 10% increase in 2011 and here is the breakdown of what I got:

Piston: list was $193.81, my price was $145.96 which included the ring set

STD. Rod was $77.96

Gasket set was $39.85

In addition, to bring the crank back to STD: $100 (weld/regrind)

Grand total: $363.77

Good thing the block was so nice.

Even though I prefer genuine Kohler parts, the economics of this rebuild are still a bit high. But when its done and running well, I will tend forget about the cost....a little.

Tom

:thumbs:

[rmaynard 14,906]

Tom,

Thanks for all that info.

[rmaynard 14,906]

Okay, the next chapter of the story is about to unfold.

I contacted Brian Miller of the infamous GardenTractorPullingTips.com website, and he actually responded to my inquiry. He said that some rings expand more than others and perhaps that is why both sets of rings had larger gaps. He also said that performance engines have the gaps set at .045, and that I should not worry about the gaps that I have.

However, in the meantime, I just won an auction on eBay for a new Kohler Brand .020 piston and rings for $20.02 plus S&H.

So I am going to wait on them to arrive, check the end gaps and the fit of the piston, and go from there.

Thanks for all the responses. I will update as soon as I have more info.

[can whlvr 991]

20 bucks is a really good deal :thumbs:

[tommy3horse 3]

Great snag on those parts Bob. Maybe the K341 stuff is a bit steeper $ than the others I have rebuilt in the past several years. (K301 x 2, K321)

Good luck on your rebuild, Bob.

Tom

:thumbs:

[VinsRJ 721]

I contacted Brian Miller of the infamous GardenTractorPullingTips.com website, and he actually responded to my inquiry........ and that I should not worry about the gaps that I have.

Like I said

I am interested in the Kohler parts outcome. For $20 thats a good deal.