Building A looper Beast

[R Austin]

whats the reason not to go with a keystone ring?

I personally do not like keystone rings. After having owned and operated a Marine Sales and Service business for 13 years I saw a lot of broken rings. Most in OMC engines. Why, because they were keystone rings. That is MY LONE opinion. They are as advertised a pressure backed ring, I guess. However think about what happens in a cylinder with ring and cylinder wear. Put to Dixie cups together and then pull apart. How much do you have to pull before you have a lot of clearance.
As that ring and cylinder wear you have a ring that has lost control of groove clearance. Mercurys with a straight cut groove could wear a lot out of cylinder and ring and still be tight in the groove clearance. If the ring is under constant pressure maybe, however once across the exhaust port, that pressure is lost and the ring becomes drag and goes to the top of the groove and then back as the piston changes direction. Again MY OPINION.

The number 2 ring in this reworked piston is a keystone ring, the standard Wiseco production, Mercury ring. Why did I leave the keystone ring in. Three reasons: 1, I set the bore on the engine at 2.867 which tightens the ring in the groove. 2. The engine runs cooler and has better lubricating oil with the caster oil. 3. The engine will not be run the many hours that a family weekend motor that rusts the cylinder walls between weekend runs.

The Dykes ( L ring ) has near zero wall tension and is normally setup with zero end gap. The ring seats so fast that it has its clearance run in. I turned the new ring with an OD of 2.877 and when the ring was complete I parted the ring with a .04 Dremmel cut off wheel. Placed in the cylinder it had zero end clearance. I set them at .003 end gap just to be safe. The wider ring will carry better over the port than the Keystone ring. The anti-rotation pins are 180 degrees apart. I will put the end gap of the Dykes ring on the land between the exhaust ports.

[Powerabout]

I personally do not like keystone rings. After having owned and operated a Marine Sales and Service business for 13 years I saw a lot of broken rings. Most in OMC engines. Why, because they were keystone rings. That is MY LONE opinion. They are as advertised a pressure backed ring, I guess. However think about what happens in a cylinder with ring and cylinder wear. Put to Dixie cups together and then pull apart. How much do you have to pull before you have a lot of clearance.
As that ring and cylinder wear you have a ring that has lost control of groove clearance. Mercurys with a straight cut groove could wear a lot out of cylinder and ring and still be tight in the groove clearance. If the ring is under constant pressure maybe, however once across the exhaust port, that pressure is lost and the ring becomes drag and goes to the top of the groove and then back as the piston changes direction. Again MY OPINION.

The number 2 ring in this reworked piston is a keystone ring, the standard Wiseco production, Mercury ring. Why did I leave the keystone ring in. Three reasons: 1, I set the bore on the engine at 2.867 which tightens the ring in the groove. 2. The engine runs cooler and has better lubricating oil with the caster oil. 3. The engine will not be run the many hours that a family weekend motor that rusts the cylinder walls between weekend runs.

The Dykes ( L ring ) has near zero wall tension and is normally setup with zero end gap. The ring seats so fast that it has its clearance run in. I turned the new ring with an OD of 2.877 and when the ring was complete I parted the ring with a .04 Dremmel cut off wheel. Placed in the cylinder it had zero end clearance. I set them at .003 end gap just to be safe. The wider ring will carry better over the port than the Keystone ring. The anti-rotation pins are 180 degrees apart. I will put the end gap of the Dykes ring on the land between the exhaust ports.

I see the logic, thanks
I thought the issue to get over the increased rig groove clearance in a keystone is the acceleration of the piston will push the ring out as it sits on the sloped groove?

[narrowminded]

What material did you use to make the rings

[R Austin]

I made the rings from a LA steel sleeve. I have to take some time to catch up on posting to this thread. I have got a couple of things done, but progress has been slow with our work load. The engine has been completely cleaned and ready for final assembly which I plan to do this weekend. Will try to catch up on Sunday night.

[R Austin]

I am surprised that I was not challenged on the piston ring material. I was not comfortable running the same material in the ring as the liner was made from. After talking to some ring manufactures and trying to buy an iron tube to cut rings from, I checked with old reliable McMaster Carr and sure enough I could buy a 3 inch OD cast ductile iron rod. Down side, I had to bore the thing out to the ring inside diameter. I do feel better with the ductile iron as it is softer than the sleeve and will seat in and were better.

I did start the assembly over the weekend and will attach a series of the assembly pics as I will also have to make the balance of the accessories, fuel inlet log, finish carbs, trigger timing linkage, ect ect.

[R Austin]

Adding some more of the assembly pictures. The lower unit drive shaft has been shortened and re-splined. Also did the welding on the gearcase over the week end and is nearing completion of the machining. Pictures of the lower unit work will follow shortly.

[Powerabout]

wow
Thats got to be close to 250hp potential there...

[R Austin]

Just a quick upload of a few more assembly pictures . Wiring, top main lubrication fittings, Fuel tubing and trigger linkage.

[Aeroliner]

What an exceptional engine project this looper undertaking is. One can only wonder how many man hours have gone into this labor of love? With all the care in the design and the craftsmanship in the machining it will truly is going to be a powerhouse. I guess we could see between 3.5 and 4 HP per cubic inch. What a ride this engine is going to give the pilot! Looking forward to the first run and boat testing.

Alan

[PaleRider]

One word kept coming to me with each picture I saw while scrolling down > WOW!!! This is absolutely superb craftsmanship! I would love to see and hear this engine run. Again, WOW!!!