: reuse pistion rings?



smooththg6969
11-26-06, 11:48 AM
I posted In another thread about my block being cracked. I have another block now that I am building up and want to know if can I reuse the pistion rings from my old block to the new block? both blocks show the original hone pattern I just dont want to waste money if I can reuse rings.

zonie77
11-26-06, 12:31 PM
It is not advisable. They do wear in and take a "set" to the original cylinder.

That being said. It's possible that itcould work, but if it doesn't you have to tear the engine apart to fix it. My opinion...buy new rings. Did you buy a block with the pistons/crank still in or a bare block?

The bearings are NOT reuseable, even if they look good.

smooththg6969
11-26-06, 01:34 PM
Yea I got a block with the lower end still in it but I took it out because the bearings where shot It took my whole body weight to the get the block to turn over. one other thing, the new block I got has some rust in one of the bores from the hg failing I think a light dingleberry hone should take care of it would that harm the block in any way being you cant bore n* blocks?

Submariner409
11-26-06, 01:54 PM
:tisk: Spend the money on the best set of replacement rings you can't afford. If you're doing the work yourself, file fit each ring to its piston and bore. Better to have a professional shop, with the correct gauges and ring gappers, do that sort of machine work. The LAST thing you want is a N* with poorly fitted rings. Don't skimp on bearings and seals, either. A N* is a carefully engineered piece of machinery, and you can screw it up royally with a "budget" rebuild unless you are one great mechanic with a skrillion dollars' worth of tools. Keep everything CLEAN and use assembly lube.

dkozloski
11-26-06, 02:06 PM
The honing process used in Northstar engines is very carefully engineered. There is first a coarse hone for oil retention followed by a fine hone to produce plateaus for long life. I'd use my "Sunnen" rigid hone and 240 grit stones. There are oversize pistons and rings available for Northstars in +0.010.

smooththg6969
11-26-06, 02:54 PM
so far im going as carefully as possable to get this engine back together. the only thing im really worried about is the honing process can anyone give me a good method to follow?

dkozloski
11-26-06, 03:11 PM
so far im going as carefully as possable to get this engine back together. the only thing im really worried about is the honing process can anyone give me a good method to follow?
I think the process is spelled out in some of the the factory service manuals. I found one reference that says to start with 100 grit stones and follow with 240 after a rebore. Wash the block after you're through with hot water, detergent and a scrub brush. To keep the metal removal and subsequent oversizing to a minimum I'd go with 240's only. The 100 grit honing should still be there.

smooththg6969
11-26-06, 03:47 PM
thanks this will be done on one bore only the one that has the rust

eldorado1
11-26-06, 04:59 PM
From what I have read, you want to use aluminum oxide stones (NOT SiC), with no finer than 280 grit. A torque plate is not necessary.

Make sure the guys know what they're doing.... this isn't something to farm out to the lowest bidder.

chevelle
11-26-06, 09:08 PM
You don't really want nor need to "start over" on the honing process to remove the rust. You cannot duplicate the factory honing process in the field anyway since the factory uses diamond stones.... Trying to start over with rough stones and then to try and replicate the plateau hone would be a disaster and would leave the cylinder oversize anywya.

Just touch it with the dingle berry hone to clean the rust off. You can use some 600 wet/dry paper locally by hand to clean the worst of the rust off and then finish with the dingle berry hone. I would normally never recommend a dingle berry hone for "honing" but all you want to do is to clean the bore. Just lubricate the bore with some mineral spirits and brush it with the dingle berry hone in an electric drill a few swipes and it should be fine. Don't worry if the bore is simply discolored from the corrosion. Just clean the red rust off and make sure that there are no scratches or high spots from scuffing on the cylinder wall.

How many miles on your original rings...??? Chances are that they are fine and will work fine in the different block. The rings mate to the piston ring lands...specifically the sides of the ring lands in the pistons so you don't want to swap them around on the different pistons. Just take the entire piston assembly from the old block and install it in the new block. They will be fine. Unless you are building a max effort race engine you will never notice the difference with the rings.

Just make sure everything is squeeky clean when you begin to reassemble. Getting all traces of the honing and cleaning grit and gunk out of the bores and the block is far more important.


If you look at the second ring face you can see the polish on it where it is "working" against the cylinder wall. Usually you will see the untouched edge of the ring with only about 25% of the width of it polished. That would make the ring about 25% worn, roughly. As long as there is some of the working face of the ring that is dull or unpolished then the ring is perfectly serviceable and I wouldn't hesitate to reuse it. Once the ring face shows polish over the entire width of the ring face then it is starting to be on the "worn" side and would be considered for replacement. That is usually about the 250K mile point.

Consider that the factory machines and hones all the bores and installs rings into them completely randomly. Taking a ring out of one bore and putting it into another really is fine as long as the ring has adequate tension and is showing partial face contact. The ring never really touches the actual bore surface due to the fact that it is riding on a layer of oil so it really doesn't "mate" to the cylinder wall rather it mates to the sides of the piston ring land. The ring constantly turns on the piston anyway so it couldn't "mate" to any specific point on the cylinder wall since it turns in the groove all the time.

Ranger
11-26-06, 09:39 PM
I have heard that the rings turn in the lands before. I never realized that and that being the case, what is the reason for staggering the ring gaps 180 degrees during installation?, or is that another "old school" thing I have simply not kept up with?

dkozloski
11-26-06, 10:14 PM
I have heard that the rings turn in the lands before. I never realized that and that being the case, what is the reason for staggering the ring gaps 180 degrees during installation?, or is that another "old school" thing I have simply not kept up with?
I put the oil ring gap towards the top on the opposed aircraft engines I overhauled because it had expanders behind it that kept it from turning. If the plane was parked on a side slope it kept oil out of the combustion chamber. The only time I ever saw ring gaps lined up was when a cylinder had a bad score that the rings caught on as they rotated. I knew that the score was there when the engine was put together.

smooththg6969
11-26-06, 10:41 PM
well Im getting confused here, I want to lean towards chevelle's method but most other people say never reuse rings and use speical hones. there is only one bore with rust in it. I will be swapping the bottom end from my old block it turned like butter. it would be nice to reuse rings but I already smoke and dont want my car smoking. The real thing that im worrying is not the pistion rings but cleaning up that one bore. now im kindof thinking of buying a used engine and just putting that in the car but Im guessing thats A hit or miss item not knowing the history of a used motor.

dkozloski
11-26-06, 11:07 PM
well Im getting confused here, I want to lean towards chevelle's method but most other people say never reuse rings and use speical hones. there is only one bore with rust in it. I will be swapping the bottom end from my old block it turned like butter. it would be nice to reuse rings but I already smoke and dont want my car smoking. The real thing that im worrying is not the pistion rings but cleaning up that one bore. now im kindof thinking of buying a used engine and just putting that in the car but Im guessing thats A hit or miss item not knowing the history of a used motor.
I've removed and replaced dozens of aircraft cylinders for inspections and valve touchup and seen hundreds more done by others with never a problem from reusing the rings. It was standard practice in my shop. Rust in a cylinder is no big deal. It's not a problem until the pits get big and deep enough to bridge the rings. It looks alarming but never seems to develope into an issue.

Ranger
11-27-06, 11:31 AM
You can take Chevelle's & Koz's word to the bank.

chevelle
11-27-06, 02:58 PM
It is good practice to misalign all the ring gaps during a build but the rings will move around anyway. Chances are that the gaps will never all line up if the rings are moving and even if the gaps did line up the rings would move away from this situation....and it would statistically be unlikely and would only happen on one piston at a time as the odds of ALL the rings lining up on ALL the pistons is astronomically small. If there is a scratch or severe discontinuity in a bore it is quite common for the ring end to "catch" on it and not migrate away...so eventually all the rings end up rotating and catching on the same discontinuity. Even a severely out of round bore can cause this....as the rings will rotate and find the point of discontinuity and stay there. At continuous high speed the rings rotate almost continually. I have seen studies where the rings were doped with a radiometric tracer and a "geiger counter" outside the block could actually measure the RPM of the rings moving around the piston as the engine ran at high RPM. Unless the rings are pinned (like a two stroke) they will definitely move so the idea of not lining up the gap, while a good idea for the initial build, is really not technically necessary.

Koz is exactly right. As long as the corrosion leaves only pits (low spots) and the pits do not bridge the ring (they are not wider than the ring width) they really will not cause a problem. There will be a slight increase in oil consumption due to the oil being trapped in the low spots and then partially being consumed but the effect is pretty minor unless the pitting is very severe. The main thing is to not have any high spots in the cylinder. Clean it with 600, touch it with the dingle berry hone and run it. For a passenger car engine anything more is really wasted effort and time and money....especially for a higher mileage rebuild. If you were trying to win Indy it would be a different deal but the passenger car engines are pretty forgiving in this respect.

Just make sure all the rings move freely in the grooves when the pistons are out. Any sticking in the ring grooves due to carbon build up will cause smoking and oil consumption.

The block and lower crankcase are a matched set so you MUST keep the block and original lower crankcase together. I assume when you mention using your old bottom end you mean the crank/rods/pistons and not the lower part of the block. The main bearings are reuseable if they are in good shape. The rod bearings MUST be replaced due to the excessive crush on them. Once heat/thermal cycled under load they deform and will fail if unclamped and reused. Always use new rod bearings.

dkozloski
11-27-06, 05:29 PM
Aircraft engines with nitride hardened cylinder bores are very prone to rust in coastal climates if not operated regularly. After being dormant for an extended period of time and then started the oil can look like red lead paint but with a little running and an oil change ,all is well.

Ranger
11-27-06, 08:24 PM
"I have seen studies where the rings were doped with a radiometric tracer and a "geiger counter" outside the block could actually measure the RPM of the rings moving around the piston as the engine ran at high RPM."

Just out of curiosity, any idea what that RPM was?

dkozloski
11-28-06, 01:49 AM
"I have seen studies where the rings were doped with a radiometric tracer and a "geiger counter" outside the block could actually measure the RPM of the rings moving around the piston as the engine ran at high RPM."

Just out of curiosity, any idea what that RPM was?
Phil Irving who was the legendary chief engineer for Vincent Motorcycles claimed that they measured piston ring RPM's up to 60 RPM in a Vincent V-twin engine. I would expect it to be higher in an aircooled motor because the bore would have more taper at running temperatures. I trust you have heard of Vincent Black Shadow and Black Lightning cycles. The frames were terrible but the engines were outstanding. The answer was to put a Vincent engine in a Norton frame. The resulting NorVin was the best of the best.

smooththg6969
11-28-06, 04:59 PM
well i followed chevelles method to clean the bore with 600 grit it cleand up really well I did notice some minor pitting little specs a little smaller than a grain of salt now im waiting on the hone to arrive to see how good it looks after that i hope it doesent consume enough oil to smoke. but like I said theres very minor pitting ill try to get pics soon.

dkozloski
11-28-06, 05:24 PM
well i followed chevelles method to clean the bore with 600 grit it cleand up really well I did notice some minor pitting little specs a little smaller than a grain of salt now im waiting on the hone to arrive to see how good it looks after that i hope it doesent consume enough oil to smoke. but like I said theres very minor pitting ill try to get pics soon.
You're gonna be good to go! Not to worry!

smooththg6969
11-28-06, 05:32 PM
thanks dkozloski. I want to also thank every one for the valuble information. right now im waitin on my next check to buy bearings and stuff. I bought a whole gallon of wd 40 to keep the block clean and lubed. can anyone reccomend a assembly lube im thinking of the drugstore stuff?

eldorado1
11-28-06, 06:16 PM
drugstore stuff? I hope that doesn't mean vasoline.

dkozloski
11-28-06, 06:31 PM
drugstore stuff? I hope that doesn't mean vasoline.
I used GM EOS and 40W motor oil half and half to assemble many, many aircraft engines and never had a lubrication failure. I applied the mixture with a clean paint brush. Don't get it on the back side of bearing inserts or in bearing saddles. It will keep the inserts from mating correctly with the saddles.

eldorado1
11-28-06, 08:09 PM
Not sure why you'd want to dillute it with regular oil?

dkozloski
11-28-06, 10:57 PM
Not sure why you'd want to dillute it with regular oil?
It goes a little further and seems to stick better without draining off.

Submariner409
11-29-06, 07:52 AM
:tisk: Be very careful with WD-40 as an engine lubricant. As the stuff "dries out" it forms a sticky film, and is not a satisfactory assembly lube. WD-40 IS great for waterproofing and electrical work. Use a product specifically branded as "Assembly Lubricant"; look at Edelbrock, Comp Cams, or Joe Mondello Oldsmobile (mondellotwister.com) for advice. Assembly lubes are blended to supply short-term high stress lubrication to mechanical bearing areas. Figure a way to fill the oil passages and pressure lube the engine before you start it the first time. (Difficult without a distributor drive gear....) Look in the engine oil threads to find out how to disassemble the first oil filter for inspection after break-in.

dkozloski
11-29-06, 09:40 AM
EOS is the GM recommended assembly oil especially for cams and lifters. It has been suppiled by GM for over 50 years.

chevelle
11-29-06, 11:04 AM
Yep....use EOS. I use it straight out of the bottle, myself. EOS is available at any GM parts counter. It is, first and foremost, an assembly lube as that is what it was designed for.

Submariner409
11-29-06, 03:11 PM
DKOZ....One of the weird things about Vincents was that the front cylinder actually formed part of the yoke-downtube "frame". There was no single or double tube frame under the engine......the yoke was bolted to the cylinder head! Talk about stress. Hit a pothole, and gonzo...
Does anyone know, for sure, whether N*'s use tapered compression or oil rings? Is the top ring moly faced? You install a tapered ring upside down and you have an oil pump......
I quote the '02 Seville FSM, p. 6-340..."6. When replacing the piston rings, only install re-ring sets that have a 1.2 mm (0.047") thick nitrided steel upper compression ring and multi-piece oil rings. The top compression ring may be installed either side up. There is a locating dimple on the 2nd compresion ring near the end for identification of the top side. Install the second compression ring with the dimple facing up." ---Tapered ring, methinks, and, if worn, should not be reused.

chevelle
11-29-06, 10:18 PM
The piston ring rotation studies I remember were run on an engine operating at about 5000 RPM and I think the rotation speed of the rings on the piston was in the neighborhood of 5 or 6 RPM at light load when the rings would be less stable and much less, around 1 RPM, under full load. They don't rotate "fast" on the piston but they move around. It really depends on the specific engine, piston, ring design, etc.... The rotation would be very dependent on all those factors and more so the rotation speeds mentioned are simply ball park numbers and that is all.

The second ring is not tapered. It is a scraper style ring and the dot denotes the upper side so that the scraper feature of the bottom edge is oriented correctly.

The top ring is a square cut ring.

The field service manual being quoted is specfically aimed at the OEM piston and re-ring set. There is also a field service bulletine with somewhat contradictory information that applies to the service piston/ring that was put into service for severe oil consumption cases. that information applies to those pistons/rings and not the general population of Northstar engines.

Whether the ring is tapered or whatever it can be reused. The results will be fine unless the ring is starting to show full face contact from a lot of miles of use. Even then the ring will perform as well as it was performing in the orginal cylinder but it will not seal as good as a new ring or a less worn ring. There is very little to no risk in "reusing" the rings in another cylinder in the case in discussion here.


There are a number of motorcycles that use the engine as a stressed member of the frame like the Vincent did. The Honda CBX six cylinder motorcycle, circa 1979-82, had no frame downtubes at all and the engine was the sole structural member of the "frame" from the steering head downward. Seemed to work OK.... But the stiffest and most structural frames on streetbikes and performance bikes have full frames using the engine as bracing and not the sole structural member.

Submariner409
11-30-06, 06:47 PM
Chevelle.....Read the second sentence/paragraph of your (accurate) piston ring post, and explain the semantic difference between "scraper" and "tapered". If a ring is machined to have a slightly larger (compressed) diameter at the bottom in relation to the top of the ring, it becomes "tapered" or "scraper" depending on whether you built engines in the '60's or '90's. Picky, picky....(FSM = Factory Service Manual).
Is there any way to get factory people to listen to thousands of years of experience posted herein???

dkozloski
11-30-06, 07:37 PM
Chevelle.....Read the second sentence/paragraph of your (accurate) piston ring post, and explain the semantic difference between "scraper" and "tapered". If a ring is machined to have a slightly larger (compressed) diameter at the bottom in relation to the top of the ring, it becomes "tapered" or "scraper" depending on whether you built engines in the '60's or '90's. Picky, picky....(FSM = Factory Service Manual).
Is there any way to get factory people to listen to thousands of years of experience posted herein???
I think sometimes the name changes depending on what the ring is intended to do. Tapered face if it's primarily a compression ring or scraper if used for oil control. Sometimes a scraper is used below the piston pin to put the bottom ring ridge below aluminum piston pin plugs to keep from shaving the ends off.

Submariner409
11-30-06, 08:01 PM
smooththg69..........Read all of this thread and put it your experience folder. There's a lot of gold in here, and it took us a lot of years for us to learn.

chevelle
12-01-06, 10:19 PM
Chevelle.....Read the second sentence/paragraph of your (accurate) piston ring post, and explain the semantic difference between "scraper" and "tapered". If a ring is machined to have a slightly larger (compressed) diameter at the bottom in relation to the top of the ring, it becomes "tapered" or "scraper" depending on whether you built engines in the '60's or '90's. Picky, picky....(FSM = Factory Service Manual).
Is there any way to get factory people to listen to thousands of years of experience posted herein???



Actually it is not like that at all...more to it than just semantics. Scraper rings are different from tapered rings. Tapered rings are as you describe in general. A specific scraper ring, like the Northstar and many european engines use for the second or middle ring, actually has a reduced diameter offset or step in the ring face on the bottom side. It is a distinct feature in the face of the ring...not just a simple taper. These type rings with a step in the face are very aggressive for oil control. Combined with the scraper feature in the ring face you will often see a slight reduction in the ring land diameter below the scraper ring to give the oil some place to go.

After a quick google search of "scraper piston rings" I found the following reference and many others..... http://www.federal-mogul.com/federal-mogul/Templates/Template_D2.aspx?NRMODE=Published&NRORIGINALURL=/en/OETechnology/Powertrain/PistonRings/&NRNODEGUID={4329E109-DD3E-48D4-B612-EDACB0FAE2A0}&NRCACHEHINT=Guest&Tab=Products









Uh....exactly what is posted here that you think the "factory" might not be aware of....or....what should they be made aware of.....LOL.

dkozloski
12-01-06, 11:28 PM
Actually it is not like that at all...more to it than just semantics. Scraper rings are different from tapered rings. Tapered rings are as you describe in general. A specific scraper ring, like the Northstar and many european engines use for the second or middle ring, actually has a reduced diameter offset or step in the ring face on the bottom side. It is a distinct feature in the face of the ring...not just a simple taper. These type rings with a step in the face are very aggressive for oil control. Combined with the scraper feature in the ring face you will often see a slight reduction in the ring land diameter below the scraper ring to give the oil some place to go.

After a quick google search of "scraper piston rings" I found the following reference and many others..... http://www.federal-mogul.com/federal-mogul/Templates/Template_D2.aspx?NRMODE=Published&NRORIGINALURL=/en/OETechnology/Powertrain/PistonRings/&NRNODEGUID={4329E109-DD3E-48D4-B612-EDACB0FAE2A0}&NRCACHEHINT=Guest&Tab=Products









Uh....exactly what is posted here that you think the "factory" might not be aware of.....LOL.
FWIW, Most of the scraper rings I encountered in aircraft had a chamfer on the top on the inside rather than a step on the bottom on the outside. This gives the ring a twisting action for scraping. Reusing worn pistons in Franklin(Aircooled Motors) engines with cast iron cylinder liners would sometimes produce a scraping action that was so severe that it would short out the sparkplug gaps with cast iron chips from this same twist.

chevelle
12-02-06, 08:17 PM
Yea, probably that is where the "semantics" comes into play.

In the piston/piston ring industry speak a "scraper" ring typically has a distinct step in the face of the ring on the lower edge. This moves the edge contact of the ring partway up the ring face, multiplies the contact force of the ring's scraping edge and adds a relief (the "step" that is cut out" for the oil the scraper edge generates.

Certainly tapered rings "scrape" to varying degrees...that is the whole purpose of the taper whether it be on the sides or a bevel on the back edge....due to the twisting of the ring as the piston moves up and down. But, usually in discussion and description of rings a "scraper" ring would have the step.

Some very aggressive scraper rings used in European engines have the step in the form of a hook shaped step that increases the volume for oil to escape in the step area and changes the angle of approach of the step from a square edge (typical square step) to move of a cutting edge. These rings will really remove oil from cylinder walls and are often used/required where piston oil squirters are putting copius amounts of oil on the cylinder wall. On "normal" engines they will dry the cylinder wall so well they can actually cause cylinder wall lubrication problems.

The second ring does far more in terms of oil control than most people realize. They are not just "second" compression rings.

The oil rails and the second ring will typically remove most of the oil from the cylinder wall surface so if it is very smooth then the wall can actually be too "dry". This is where the honing pattern is critical to leave a pattern of "valleys" in the surface that will retain oil for lubrication.

dkozloski
12-02-06, 10:52 PM
Yea, probably that is where the "semantics" comes into play.

In the piston/piston ring industry speak a "scraper" ring typically has a distinct step in the face of the ring on the lower edge. This moves the edge contact of the ring partway up the ring face, multiplies the contact force of the ring's scraping edge and adds a relief (the "step" that is cut out" for the oil the scraper edge generates.

Certainly tapered rings "scrape" to varying degrees...that is the whole purpose of the taper whether it be on the sides or a bevel on the back edge....due to the twisting of the ring as the piston moves up and down. But, usually in discussion and description of rings a "scraper" ring would have the step.

Some very aggressive scraper rings used in European engines have the step in the form of a hook shaped step that increases the volume for oil to escape in the step area and changes the angle of approach of the step from a square edge (typical square step) to move of a cutting edge. These rings will really remove oil from cylinder walls and are often used/required where piston oil squirters are putting copius amounts of oil on the cylinder wall. On "normal" engines they will dry the cylinder wall so well they can actually cause cylinder wall lubrication problems.

The second ring does far more in terms of oil control than most people realize. They are not just "second" compression rings.

The oil rails and the second ring will typically remove most of the oil from the cylinder wall surface so if it is very smooth then the wall can actually be too "dry". This is where the honing pattern is critical to leave a pattern of "valleys" in the surface that will retain oil for lubrication.
Some aircraft applications have oil drain holes drilled in the piston below a scraper ring, especially with oil cooled pistons.