The International Cessna^® 170 Association

Anyone have experience with gapless piston rings. I've heard of a few Franklin engine owners using them with just a log book sign off. I heard that a DER reviewed them and indicated they are a minor modification that does not require a 337 or STC.

When I put the phrase "gapless piston rings" (in quotes) into the yahoo search engine, I get about 450 hits. When I add "teledyne" or "lycoming" to the search I get zip. Maybe TCM and Lycoming haven't heard of them yet?

Miles

Try GOOGLE, you'll find it there!

djbaker wrote:Try GOOGLE, you'll find it there!

Well, I got two hits there. Onewas heresay, that he had heard of someone useing gapless piston rings. No real info there.

The otherwas by someone who had actually used them, though not in a lycoming, continental, or franklin:

I have used the gapless rings in big bore vw aero engines and found that by using them in both compression grooves was not a good idea. Too much oil control. Not a good idea especially in a steel cylinder like Continentals. Overall I would have to stay with the regular rings as the comparative leak rates were about the same. Just did my 65 and used the Superior stock rings.

Not exactly a glowing reccommendation. I may be accused of being a borderline luddite, but it seems that those guys that designed our engines way back when had a pretty good idea what they were doing.

Miles[/url]

I just did the Google search and found that they use them only on the second compression ring. Claims to reduce oil consumption and prolongs oil life by reducing blowby, might add a few hp.

Sounds like a solution to a problem that doesn't exist.
I'd rather see my upper cylinder lubricated well.

With GOOGLE you get Performance Engine, SuperCub.ORG, Mustangaero/messages, Bower fly baby and Harry Fenton on Contential Engines all talking about gapless rings. At our field we have an LSA that has a 0200 which the owner claims has 135HP by porting and balancing the engine. Seems to fly well, but I'm no expert. The websites I mentioned above talk about 0235s with 150 or more HP @2800rpm. It's logical that any engine can be made to have more HP, but I think I'd go for a strong engine. One that measures up to the original factory specs rather than add HP at the cost of stability.

Claims of increased horsepower are meaningless unless they can substantiate the matter. If an engine makes 100 hp at 2700 rpm with a particular prop...then it makes that hp under those conditions regardless of whether someone "ports and polishes" or does any other magical incantations over it.

gahorn wrote:Claims of increased horsepower are meaningless unless they can substantiate the matter. If an engine makes 100 hp at 2700 rpm with a particular prop...then it makes that hp under those conditions regardless of whether someone "ports and polishes" or does any other magical incantations over it.

Good point, George. It takes a certain amount of power to drive the prop at a certain RPM, no matter what the engine is capeable of putting out.
Unless you put the engine on a dynometer, you really don't know what it can do. And how many people do that?
Many years ago Car & Driver magazine evaluated several sports cars that people had "souped up". Their test was just straight line acceleration.
None of the cars were significantly faster than a stock version, and a couple actuelly had less performance. The conclusion was, they sounded better.

I was looking over the 170 the other day and noticed that the manifold pressure gauge was showing 31 inches or so. Ouch it must be in error, then I realized I am at sea level and it can read that high -- the C145 can put out a little more hp. A lot different than living at 5,500 feet msl and every little bit of manifold pressure is welcomed.

The franklin engine guys were looking for parts and had some luck finding some high performance engine parts (rings) that would fit along with some aftermarket valves - primarly to keep them running in anticipation of parts shortages. It sounds like there is no advantage to using gapless rings other than helping to keep the lead out of the oil, and perhaps reducing/delaying the onset of 100LL induced exhaust valve sticking.

Lycon is the only one I am familiar with that does the port polish and flow balance. They do have a dyno to back it up. Also I have been around 5 or 6 motors that they did that to and they all had a higher static run up RPM afterwards. The draw back is your fuel flow goes up also.
George I agree with your statement as long as a fixed pitch prop is installed but with a constant speed prop the prop is just going to do what ever the governor tells it to do reguardless of horsepower. Ofcourse the limiting factors would be the high and low pitch stops.
Shawn