Single ring pistons question

[BmJuby]

Can someone explain how a three ring piston with one ring does not function the same as a single ring piston? Maybe in doing so explain how the single ring functions. If the one ring is there, does it not matter "behind" if there are rings or not?

Thanks,
Brandon

[laddies]

Most 3 ring pistons us straight cut rings, 1 or 2 ring piston use keystone or L rings to improve the seal of the rings. Many people have in the past collapsed 1 or 2 rings on 3 ring pistons. It's not a big secret I don't know why you didn't get a answer

[BmJuby]

Thanks

[champhotrod]

Can someone explain how a three ring piston with one ring does not function the same as a single ring piston? Maybe in doing so explain how the single ring functions. If the one ring is there, does it not matter "behind" if there are rings or not?

Thanks,
Brandon

You short circuit the ports with no ring in the grooves.

Cooper

[Art K]

I know for a fact that some people are running 3 ring pistons with just one ring in their Mod 44`s at NBRA races. They are really fast. Not quite sure how they do it and go so fast. But it has made me curious.
Art K

[Guest]

Piston rings

The piston rings do more then hold the compression, they also help with heat transfer so running a single ring in a 3 ring piston elevates the head temperature. Years gone by I used to make aluminum rings for A and B engines we ran. We ran them in the second and third grove. We also ran about .004' end gap on ring one. It required that the engine was run at lower power settings for the first hour or so. The ring filled the grove but lightly touched the cylinder walls. This way the temperature was actually lovered in that Aluminum has a better heat transfer coeficient then Iron. If you look closely at a piston in a block you will have a clear path from the intake to the exhaust port that will bleed off some crankcase compression. Intresting discussion though.

Alan

[Guest]

Pistons with open groves

I though I would post a couple photos to demonstrate the crankcase compression path available when no rings are installed in the piston. The intake side is showing the ports just at the start of the intake cycle while the exhaust side is well into the exhaust cycle. The piston was not moved for the two photo's. This was a Merc A block.

Alan

[Morris85C]

So are you saying that running one ring on a three ring piston wont work? Or the moter will not run right?

[Guest]

Rings

The basic thought is that by not filling the two lower ring groves we loose some of the crankcase compression thus loosing power. The engine most likely would run but we would not develope the maximum power output that the engine was capable of developing.

Alan

[Morris85C]

Have you ever ran a moter on a dyno with 3 rings? An then ran the same moter on the dyno with only 1 ring to see what happens.Or just ran a moter that had signal rings on a race boat to see what happens.

[bill van steenwyk]

Have you ever ran a moter on a dyno with 3 rings? An then ran the same moter on the dyno with only 1 ring to see what happens.Or just ran a moter that had signal rings on a race boat to see what happens.

I did, on a boat, and was not happy with the result. It ran much better with all three rings in place, although I was not real happy with it either way, mostly due to who worked on it to start with and some of the port work, if you want to call it that, (gouging would be a better description) that was done to start with.

BUT, it was much better with all three rings in place.

[Guest]

Piston rings

During the 60's while running BSR and BSH with a 20-H conversion I started testing my engine with various combinations of rings on the piston. At first I would put rings in a hose clamp and heat them to take the spring out of them and colapse the diameter. That helped a bit. I tested for a short time with the two lower rings removed and on my Keller it showed a loss in speed of about 2 MPH. Thats when I figured out the crankcase compression was blowing through the open ring groves. To combat that I made aluminum piston rings to fill the groves. Over time I think I sold about 1,000 aluminum rings all over the east coast. They were lighter then iron, better heat transfer and no way for the crankcase compression to vent through the grove. To get maximum performance from the engine I would start with a .015" over Mercury ring and set the end gap at .004" in a standard bore for the top ring.

Alan

[ZUL8TR]

alum rings

Alan what was the performance increase (speed, accel, etc) with the final set up with the 2 alum rings to seal crank pressure transfer and only the top ring working?

Was there any reduced gaged compression with the final setup?

[Morris85C]

Thanks Alan for the information. I run signal rings in all my moters.Even my 60cu an have no problems with horse power loss .I guess what works for one guy does not all ways work for some one else.I wish we had more guys Like you to share information on here Its good for are sport.

[thetrailergod]

1 big thing that everyone is hip on is compression, 1 of the best runnig engines I ever had , only had 70# in each cylinder, way low comparing to others , but i did run well and out front at times,you all have to remember that a compression gauge is just a tool to use and may not give the same as other gauges.and as the rpm climbs in a merc the compression builds, so realistically you really dont know how much compression you truly have at 8,000 rpm. also I was once told by a guy that has built mercs most of his life < that in a merc once you get it started you really dont have to have rings in the pistons,the oil will do all the sealing you need, hence labrith seals, just like in the center main and reed cages