Are 2 stroke OB piston rings interchangeable w/other ...

Frank Acampora said:

Really, you should go to the forum for your engine--Mercury, I assume by your post. You should state your problem there and ask for help. Do NOT assume the engine needs rings. Outboards typically get little running time compared to other engines and worn rings are not a common problem.

If you want to learn more, please visit our website Dongya.

Click to expand...

The question was related to all two strokes as I've got multiple makes laying all over the place. A substitute ring would come in handy for some of the older, obsolete makes like Elgins. I'm also bummed that a set of OB rings for two tiny 2" pistons cost more than a full set of V8 rings for a small block Chevy. Oh well.

This one in particular had a ring that fell out in two pieces when I removed the piston so it was obviously toast. That cyl had low compression and you could see through the ports that the ring was black as compared to other three that were worn silver. Believe me, I don't go looking for ring jobs.

Re: Are 2 stroke OB piston rings interchangeable w/other devices?The question was related to all two strokes as I've got multiple makes laying all over the place. A substitute ring would come in handy for some of the older, obsolete makes like Elgins. I'm also bummed that a set of OB rings for two tiny 2" pistons cost more than a full set of V8 rings for a small block Chevy. Oh well.This one in particular had a ring that fell out in two pieces when I removed the piston so it was obviously toast. That cyl had low compression and you could see through the ports that the ring was black as compared to other three that were worn silver. Believe me, I don't go looking for ring jobs.

Want more information on 2 Stroke Engine Piston Rings? Feel free to contact us.

Brutpwr said:

The tighter piston clearance and tighter ring end cap both add up to longer life and more importantly more power thru out the rev range along with less chance to build excess heat and friction which can cause seizure in extreme cases.

Click to expand...

Well I have to disagree on the ring gap. You want to open them up a touch for performance applications, at least in 4 stroke engines. While I might be wrong in a 2 stroke, here is a quick "rule of thumb" write up:

WARNING: When measuring piston ring end gap, check the gap with the rings at the top and the bottom of the bore. If the bore has taper wear (bores typically wear most at the top), the end gap will be larger at the top and smaller at the bottom of the bore. Use the bottom position to set the end gap. If you use the top of a worn bore to set the end gap, the end gap will be too small when the piston reaches the bottom of the bore. The ends of the ring may hit each other causing the ring to bind and scuff. Cylinders that have more than .003 to .005 inches of taper wear should probably be bored or honed to oversize to restore proper piston and ring clearances. Refer to the engine manufacturer's specifications for the maximum allowable taper wear.
Piston Ring End Gap Recommendations

Most piston ring manufacturers recommend a minimum end gap of .004 inches times the bore diameter for the top piston compression ring. So for a 4 inch bore, the standard end gap would be .016 inches.

For the 2nd compression ring, the standard end gap recommendation for most stock engines is typically .005 in. x the bore diameter. So for a 4 inch bore, the minimum end gap on the 2nd ring would be .020 inches.

For a modified street performance engine that generates more horsepower and heat, the end gap should be opened up a bit to compensate for increased thermal expansion. The recommendation would be a minimum top compression piston ring end gap of. to .005 inches times the bore diameter. For a 4 inch bore, the ring end gap on the top ring should be increased to .018 to .020 inches.

For the 2nd compression ring on a modified street performance engine, the recommendation is typically open up the end gap to . inches times the bore diameter. For a 4 inch bore, the 2nd ring would be gapped to .022 inches.

For a nitrous or blown racing engine, the top ring end gap sould be opened up to as much as .006 or .007 inches times the bore diameter. Now we're looking at a 2nd ring end gap of .024 to .028 inches in an engine with 4 inch bores.

For the 2nd ring on a nitrous or blown motor, the recommended ring end gap is even wider: . to . inchestimes the bore ( or 0.025 to 0.029 inches with a 4 inch bore).

The recommended ring end gap for oil rings regardless of the engine application is typically .015 inches.

Some racers believe that opening up the 2nd end gap even more (say an additional 10%) can improve overall ring sealing by allowing trapped gases to escape before they blow past the top ring and cause ring flutter at high rpm (say above to rpm).

NOTE: These recommendations are rules of thumb only. Always follow the end gap specifications recommended by the piston ring supplier or engine manufacturer.


http://www.aa1car.com/library/ring_end_gap.htm


And a PDF from SpeedPro :
And one from Wiseco :

and both state it is better to run them a bit loose than too tight.

Well I have to disagree on the ring gap. You want to open them up a touch for performance applications, at least in 4 stroke engines. While I might be wrong in a 2 stroke, here is a quick "rule of thumb" write up:WARNING: When measuring piston ring end gap, check the gap with the rings at the top and the bottom of the bore. If the bore has taper wear (bores typically wear most at the top), the end gap will be larger at the top and smaller at the bottom of the bore. Use the bottom position to set the end gap. If you use the top of a worn bore to set the end gap, the end gap will be too small when the piston reaches the bottom of the bore. The ends of the ring may hit each other causing the ring to bind and scuff. Cylinders that have more than .003 to .005 inches of taper wear should probably be bored or honed to oversize to restore proper piston and ring clearances. Refer to the engine manufacturer's specifications for the maximum allowable taper wear.Piston Ring End Gap RecommendationsMost piston ring manufacturers recommend a minimum end gap of .004 inches times the bore diameter for the top piston compression ring. So for a 4 inch bore, the standard end gap would be .016 inches.For the 2nd compression ring, the standard end gap recommendation for most stock engines is typically .005 in. x the bore diameter. So for a 4 inch bore, the minimum end gap on the 2nd ring would be .020 inches.For a modified street performance engine that generates more horsepower and heat, the end gap should be opened up a bit to compensate for increased thermal expansion. The recommendation would be a minimum top compression piston ring end gap of. to .005 inches times the bore diameter. For a 4 inch bore, the ring end gap on the top ring should be increased to .018 to .020 inches.For the 2nd compression ring on a modified street performance engine, the recommendation is typically open up the end gap to . inches times the bore diameter. For a 4 inch bore, the 2nd ring would be gapped to .022 inches.For a nitrous or blown racing engine, the top ring end gap sould be opened up to as much as .006 or .007 inches times the bore diameter. Now we're looking at a 2nd ring end gap of .024 to .028 inches in an engine with 4 inch bores.For the 2nd ring on a nitrous or blown motor, the recommended ring end gap is even wider: . to . inchestimes the bore ( or 0.025 to 0.029 inches with a 4 inch bore).The recommended ring end gap for oil rings regardless of the engine application is typically .015 inches.Some racers believe that opening up the 2nd end gap even more (say an additional 10%) can improve overall ring sealing by allowing trapped gases to escape before they blow past the top ring and cause ring flutter at high rpm (say above to rpm).NOTE: These recommendations are rules of thumb only. Always follow the end gap specifications recommended by the piston ring supplier or engine manufacturer.And a PDF from SpeedPro : http://www.aa1car.com/library/ring_info_speedpro.pdf And one from Wiseco : http://www.aa1car.com/library/ringendgap_wiseco.pdf and both state it is better to run them a bit loose than too tight.

Are you interested in learning more about Piston Ring Factory? Contact us today to secure an expert consultation!