Piston rings not seating

715Hunter

Member
Jul 28, 2022
73
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8
Missouri
Completey new here, just been reading posts as a non-member for a long time.

Anyone have experience or advice on how to get rings to seat? Really, really don't want to pull my engine back out and have the bores re-honed.

I just finished re-installing the engine in my truck. It cracked a piston at 405,000 miles, so I built it to handle more power with good longevity. I replaced the injectors at the same time as 4 of them tested bad after tearing everything down.

My break-in oil was Shell Rotella T4 15-40 with a ZDDP additive. I did not have new tuning upon initial start-up with the fresh engine and 45% over injectors, and it got probably 15 minutes of idle time right away, (broken into shorter segments.) I know this isn't ideal.
I then had to drive it for work, about 700 miles over the course of a week. During this time it developed an oil leak on the turbo, (missed torquing a drain tube bolt) and an up pipe leak. Both of these have been fixed, but it affected how I could drive. After almost 1,000 miles I finally got it tuned correctly.
All this while, I had massive blow-by out the crankcase vent. Enough to make one frame rail oily about 6' back from the hose.

After a lot of reading, I pulled the glow plugs and soaked the cylinders with penetrating oil overnight, then changed the oil to Rotella 10-30, and ran it really hard for awhile. I've put another 250 miles on it, and it still has tons of blowby. If I put my finger over the crankcase vent, it builds about 5 psi in short order, and starts pouring white smoke out the pipe.

Any ideas?? Did I glaze the cylinder walls? Am I screwed and need to start over? And what did I do wrong?
 

Chevy1925

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Oct 21, 2009
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whats your piston to wall clearance? how big is your ring gap? how was the block machined and honed? whos rings did you use? whos pistons and bore size? was the block bored over?
 
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715Hunter

Member
Jul 28, 2022
73
12
8
Missouri
Short block was built by a reputable shop local to me, so I don't know internal specs. I could probably call and find out, but their engine guy is hard to get a hold of.
We used Mahle cast pistons and rings. They had to bore .020" over.
 
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Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
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without more info, its a guess in the wind... also, dont put any oils down the cylinders and swap that engine oil out asap. its not going to fix the issue, sadly.

to me it sounds like broke oil control rings, bad piston to wall clearance, or something inside. you cant fix it from the outside.
 

715Hunter

Member
Jul 28, 2022
73
12
8
Missouri
Thanks.
I've heard of poorly seated or stuck rings being an issue on engines with mileage but it doesn't seem to really be a thing on brand new stuff.
 

Dallas S

Active member
Jun 17, 2009
485
33
28
Alberta
We had an engine assembled by a reputable Duramax builder that had similar blow by issues. It would push a cup of oil out after each dyno pull. We tore it down and found .070-.075 ring gaps…. Best guess is they put standard rings on .020 pistons. New rings fixed the blow by issue. John Deere 10-30 break in oil works well to seat the stainless rings
 
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West

New member
May 18, 2022
18
13
3
Folsom CA
Man these problems can be really painful. You try hard to do it correctly and end up starting over.
If your cylinders were honed correctly and ring gaps set properly after it was bored you should have a smooth surface for your rings to run on with a light cross hatch that helps hold oil and control the speed your rings rotate as the engine runs. Piston ring failure would cause blue smoke in your exhaust but you mentioned white smoke in your exhaust? Rings not working well can certainly cause blow by as you mentioned.

Your mention of White smoke and blowby has me thinking maybe and injector cup is leaking? Your radiator is not pressurized? I have not seen an injector cup cause blowby without also causing a coolant leak but others may know this engine better and can comment.
The modern piston rings normally seat pretty well without much work but extensive idling can cause a glazing that keeps the ring from really sealing well.
Ring break in happens best under a load. If your truck is rated to pull 12,000 pounds manufacturers say on start up to verify everything is sealed and operating normally, no leaks, oil pressure good, temperature comes up to normal and stays then take this new engine hook up a trailer at close to max capacity and go out and drive it. Pull some long hills with that load. Something that gets your turbo fully spooled up for a few minutes if possible. The Turbo pressure adds to combustion pressure, this high pressure will press the top piston ring hard into your cylinder as you pull the hill loaded. This seats the ring to the cylinder. If this does not seal your blow by you are looking at an internal issue.

In the Los Angeles repair market we started seeing the Cummins ISX engines having blow by issues after overhaul. We found the problem was a group of good mechanics that did not speak english and were all taught to idle the engine after start up for extended periods before putting the truck on the road. It was a word of mouth belief among these mechanics that created the blow by issue. Once we got the word to them to knock off the extended idle before driving the issue went away. The factory wanted them to hook the new engine to a fully loaded trailer and go drive it for 100 miles at 70% or more throttle if possible to load the rings and break them in. New Pistons and Liner Kits now have instructions telling the mechanics in English and Spanish to follow this break in procedure. Sometimes if the extended idle truck had been driven on for a while with blowby it would not recover. Sometimes if you loaded it and drove it hard up hills the rings would break in and the problem was solved. I think it had to do with how badly the rings were glazed. This assumes your rings are fitted properly and your cylinders are properly honed for the modern piston rings. Some mechanics still believe a ball hone will help your cylinders and rings seat well. They are flat wrong. The engineers say to save the ball hones for mixing paint and NEVER use them in a cylinder bore.

This also assumes all of your fuel is being burned and you are not washing the oil off your cylinder walls with excess fuel. How was your MPG in your test drives. If it was terrible you have a lot of un burned fuel that is bad for the piston rings and cylinder walls.
I agree as advised in the previous post. Run the 15-40 oil as intended by the factory.
How is your injector balance test?
Hope this helps.
Mark
 

Ron Nielson

Active member
Oct 11, 2009
684
114
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Berryton, KS
These are the specs for piston rings for my LMM as published in ALLDATADIY.COM

Piston Ring End Gap-First Compression Ring - Service Limit 1.37 mm (0.0539 in)
Piston Ring End Gap-First Compression Ring - Production Value 0.3-0.45 mm (0.0118-0.0177 in)
Piston Ring End Gap-Second Compression Ring - Service Limit 1.35 mm (0.0531 in)
Piston Ring End Gap-Second Compression Ring - Production Value 0.50-0.65 mm (0.0197-0.0256 in)
Piston Ring End Gap-Oil Control Ring - Service Limit 1.20 mm (0.0472 in)
Piston Ring End Gap-Oil Control Ring - Production Value 0.15-0.35 mm (0.0059-0.0138 in)
Piston Ring to Groove Clearance-First Compression Ring - Service Limit 0.26 mm (0.0102 in)
Piston Ring to Groove Clearance-First Compression Ring - Production Value 0.08-0.17 mm (0.0030-0.0067 in)
Piston Ring to Groove Clearance-Second Compression Ring - Service Limit 0.10 mm (0.0039 in)
Piston Ring to Groove Clearance-Second Compression Ring - Production Value 0.01-0.03 mm (0.0004-0.0012 in)
Piston Ring to Groove Clearance-Oil Control Ring - Service Limit 0.12 mm (0.0047 in)
Piston Ring to Groove Clearance-Oil Control Ring - Production Value 0.01-0.03 mm (0.0004-0.0012 in)
 
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West

New member
May 18, 2022
18
13
3
Folsom CA
The Top Piston Ring is exposed to the heat of combustion, this heat makes the ring grow so you need to have enough gap so the ring never butts even when working very hard towing heavy loads. If the top ring butts it becomes a scraper and will tear up your cylinder wall and maybe fracture a ring land. If you increase Turbo Pressure or increase fuel flow you are creating a hotter explosion which transfers more heat to that top ring. I am sure there are owners on this forum that can share the minimum clearance needed for a Duramax Turbo Diesel. The industry safe number is normally .004" of ring gap for every 1" of bore. So if your bore is 4.00" you will need .016" ring gap. If you boost with more pressure and more fuel you might increase that to maybe .020 but this is general info in the industry check to verify how tight is safe based on your tune. Since many run aftermarket tunes on bone stock engines with no trouble I think the factory top ring gap is safe until you start chasing serious HP. Maybe 450 and up? Duramax pistons have quite a bit of Piston head above the top ring and that does work to shield the top ring from the hot combustion gas so maybe the top ring can run tighter but verify with Duramax engine builders with experience before deciding what gap to run.
Second ring gaps have been proven to work best at .024 this helps manage blow by and helps the top ring seal better. Since the second ring is lower, it runs cooler and the ring gap in the 4" bore on the second ring could run safely as tight as .008". But history has proven the top ring seals better if the second ring has .024" gap maybe as much as .026.
When the Ford 7.3L Turbo diesel came out they had big problems with Oil Control. The Ring pak was not sealing as it should so the trucks were burning excess oil. This was solved 100% by opening the second ring gap to .024 to .026. Sealed Power Engineering helped Ford solve that issue and then shared what they learned with Performance Engine Builders who quickly changed the second ring gaps to a wider gap. It became the industry standard because it works. If you read old literature you will be told to run a tight second ring gap but that advice is obsolete.
Mark
 

715Hunter

Member
Jul 28, 2022
73
12
8
Missouri
The Top Piston Ring is exposed to the heat of combustion, this heat makes the ring grow so you need to have enough gap so the ring never butts even when working very hard towing heavy loads. If the top ring butts it becomes a scraper and will tear up your cylinder wall and maybe fracture a ring land. If you increase Turbo Pressure or increase fuel flow you are creating a hotter explosion which transfers more heat to that top ring. I am sure there are owners on this forum that can share the minimum clearance needed for a Duramax Turbo Diesel. The industry safe number is normally .004" of ring gap for every 1" of bore. So if your bore is 4.00" you will need .016" ring gap. If you boost with more pressure and more fuel you might increase that to maybe .020 but this is general info in the industry check to verify how tight is safe based on your tune. Since many run aftermarket tunes on bone stock engines with no trouble I think the factory top ring gap is safe until you start chasing serious HP. Maybe 450 and up? Duramax pistons have quite a bit of Piston head above the top ring and that does work to shield the top ring from the hot combustion gas so maybe the top ring can run tighter but verify with Duramax engine builders with experience before deciding what gap to run.
Second ring gaps have been proven to work best at .024 this helps manage blow by and helps the top ring seal better. Since the second ring is lower, it runs cooler and the ring gap in the 4" bore on the second ring could run safely as tight as .008". But history has proven the top ring seals better if the second ring has .024" gap maybe as much as .026.
When the Ford 7.3L Turbo diesel came out they had big problems with Oil Control. The Ring pak was not sealing as it should so the trucks were burning excess oil. This was solved 100% by opening the second ring gap to .024 to .026. Sealed Power Engineering helped Ford solve that issue and then shared what they learned with Performance Engine Builders who quickly changed the second ring gaps to a wider gap. It became the industry standard because it works. If you read old literature you will be told to run a tight second ring gap but that advice is obsolete.
Mark
Mark , good info on ring gaps. I always love to learn more. I am starting to get a feel for what a break-in should look like. Since this is my first time it was a bit cloudy even with lots of reading.
On this generation Duramax, there is no injector cup. I do seem to be losing a very small amount of coolant, but it's hard to tell as I've only added a pint twice in the last 500 miles. I have towed more since last posting, with little to no improvement. It does smoke less under normal driving now.
 

715Hunter

Member
Jul 28, 2022
73
12
8
Missouri
I'm try to post a video for an idea of the smoke and blowby.

Balance rates show no indication to speak of, my spread is +1.25 to - 1 in park, +.90 to -1.25 in gear.

Checked compression this morning. Every cylinder is between 260 and 280, hot.

My last thought here is this: while I had the short block on the stand, we got some water standing on the floor of the shop where it was stored, bringing the moisture up. I got some spotty surface rust on a few exposed parts of rods, corners of the block, etc. Is it possible that the first ring rusted solid in its groove?
 

West

New member
May 18, 2022
18
13
3
Folsom CA
Compression is the same in all 8 cylinders so no top ring is stuck in its grove. That video is pretty spooky. That is a ton of smoke from plugging that tube. I am guessing you plugged the PCV vent tube? Who did the bore and hone on the block? Rings will not seal on a bad bore and hone job. Do you know what the top ring gap was on install? The Rings and ring grooves should have been lubricated on install with Assembly lube or at least a quality oil so they should not rust at all. It takes a long time for metal coated with oil to show any rust.
What do they claim your Piston to Bore clearance to be. If Mahle claims you need .003 piston to cylinder wall clearance your rings are normally set to fit that gap right out of the box. If your builder decided to increase that piston to wall clearance to maybe .005 the piston ring gaps increase by the factor of Pie or 3.14. So your bore size increase of .002 can cause the piston ring gaps to grow by 3.14 x .002 = .0063. So a top ring gap of .016 + .0063 becomes .0223 It does not seem like much but any pressure going past the top ring is Blow By. A larger top ring gap leaves lots of blow by. Racers I knew who were trying to max out their engine power would run the tightest top ring gap they could without butting the ring gaps. Race engines are sometimes rebuilt several times per race season. They would start with a known safe number on the top ring gap and with every tear down they would tighten the ring gap by .001 or less and record that information. At some point on tear down they would find witness marks of the ring starting to touch or close the gap under high heat/hard acceleration. On this tear down they would open that ring gap by a 1/2. or .0005. a half thousanth. Now they had the perfect ring gap for max power in the engine. At this point they made the best power with the least amount of blow by. Serious racers can play this game but for us normal folks you build the engine using KNOWN safe ring gaps for the best performance without ever butting the rings in operation.
Reasons rings don't seal.
- Bad bore finish, Rings need a good cross hatch, the cross hatch controls the amount of oil on the cylinder wall and the speed at which the ring spins while running. You want a slow spinning ring while you run, it drags oil accross the ring face and maintains a better ring seal. Too steep of hone finish maybe 70* angle and the rings spin fast, don't seal well and wear the ring lands in the pistons. Too flat of a cross hatch and the rings spin slow so they don't drag oil and don't seal well. What is to flat, maybe 25* can do this. Most modern engines use a cross hatch angle of 45 to 60*. It does vary by application and operating RPM. So a Corvette engine revving 7,000 RPM might have a different cross hatch angle than a Duramax with a max RPM of 4,000. The amount of oil necessary to lubricate the piston also varies by engine design. Hard working low RPM engines need more oil on the bore than a high speed low torque engine. Deeper grooves in the cross hatch hold more oil than shallow groves in the cross hatch. All things to consider when building your engine.
- Bad Hone, same as bad bore finish but in this case if the operator does not use enough pressure on the hone while it works or if the honing fluid is really dirty and overdue for a change the cross hatch looks good but under a microscope you can see the grooves are deeper in one direction than the other. I forget which cuts deeper but the cross hatch on the up and down stroke are not the same and it leaves a finish that makes the rings spin fast which promote ring wear and give a lousy ring seal. Using the wrong stone in the hone can cause bad blow by also. Hard cylinder walls need to be cut with a unique stone, use the wrong one and the cross hatch will be bad.
- Too Rough of a hone For many years machine shops thought you needed a rough bore finish to break in your rings. This is very old advice and went out of school about 1980. Since 1980 rings have started lasting longer and longer, some go 1 million miles today without blowby or oil consumption. They seal on a very smooth surface compared to the 1980 finish.

The days of using a hand hone or a ball hone to rebuild an engine are long gone. (40 years long gone) You must use modern tools with a good hone operator to get OEM type long life piston ring wear and performance.
 
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Bdsankey

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The Top Piston Ring is exposed to the heat of combustion, this heat makes the ring grow so you need to have enough gap so the ring never butts even when working very hard towing heavy loads. If the top ring butts it becomes a scraper and will tear up your cylinder wall and maybe fracture a ring land. If you increase Turbo Pressure or increase fuel flow you are creating a hotter explosion which transfers more heat to that top ring. I am sure there are owners on this forum that can share the minimum clearance needed for a Duramax Turbo Diesel. The industry safe number is normally .004" of ring gap for every 1" of bore. So if your bore is 4.00" you will need .016" ring gap. If you boost with more pressure and more fuel you might increase that to maybe .020 but this is general info in the industry check to verify how tight is safe based on your tune. Since many run aftermarket tunes on bone stock engines with no trouble I think the factory top ring gap is safe until you start chasing serious HP. Maybe 450 and up? Duramax pistons have quite a bit of Piston head above the top ring and that does work to shield the top ring from the hot combustion gas so maybe the top ring can run tighter but verify with Duramax engine builders with experience before deciding what gap to run.
Second ring gaps have been proven to work best at .024 this helps manage blow by and helps the top ring seal better. Since the second ring is lower, it runs cooler and the ring gap in the 4" bore on the second ring could run safely as tight as .008". But history has proven the top ring seals better if the second ring has .024" gap maybe as much as .026.
When the Ford 7.3L Turbo diesel came out they had big problems with Oil Control. The Ring pak was not sealing as it should so the trucks were burning excess oil. This was solved 100% by opening the second ring gap to .024 to .026. Sealed Power Engineering helped Ford solve that issue and then shared what they learned with Performance Engine Builders who quickly changed the second ring gaps to a wider gap. It became the industry standard because it works. If you read old literature you will be told to run a tight second ring gap but that advice is obsolete.
Mark
SoCal reccomends the following for a cast piston:

Top ring clearance of 0.012-0.018" (min)
2nd ring clearance of 0.020-0.026" (min)
Oil ring clearance is to have no ring butting

Bore Sizes:
Std - 4.055-4.056"
+0.020 - 4.0755-4.0760"
+0.040 - 4.0955-4.0960"
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
21,106
4,841
113
Phoenix Az
I'm try to post a video for an idea of the smoke and blowby.

Balance rates show no indication to speak of, my spread is +1.25 to - 1 in park, +.90 to -1.25 in gear.

Checked compression this morning. Every cylinder is between 260 and 280, hot.

My last thought here is this: while I had the short block on the stand, we got some water standing on the floor of the shop where it was stored, bringing the moisture up. I got some spotty surface rust on a few exposed parts of rods, corners of the block, etc. Is it possible that the first ring rusted solid in its groove?

na, this isnt a flash rust issue. this is a bad machining issue. balance rates wont show anything because the power balance between cylinders is good. When you look at balance rates, you need to look at the main injection flow rate as well, thats how much fuel overall is being used. a healthy engine and injection system will have a main rate around 8-9mm3.

with compression that low, im not surprised at your issues. that is BAD. gotta tear that engine down and start micing things out.

Compression is the same in all 8 cylinders so no top ring is stuck in its grove. That video is pretty spooky. That is a ton of smoke from plugging that tube. I am guessing you plugged the PCV vent tube? Who did the bore and hone on the block? Rings will not seal on a bad bore and hone job. Do you know what the top ring gap was on install? The Rings and ring grooves should have been lubricated on install with Assembly lube or at least a quality oil so they should not rust at all. It takes a long time for metal coated with oil to show any rust.
What do they claim your Piston to Bore clearance to be. If Mahle claims you need .003 piston to cylinder wall clearance your rings are normally set to fit that gap right out of the box. If your builder decided to increase that piston to wall clearance to maybe .005 the piston ring gaps increase by the factor of Pie or 3.14. So your bore size increase of .002 can cause the piston ring gaps to grow by 3.14 x .002 = .0063. So a top ring gap of .016 + .0063 becomes .0223 It does not seem like much but any pressure going past the top ring is Blow By. A larger top ring gap leaves lots of blow by. Racers I knew who were trying to max out their engine power would run the tightest top ring gap they could without butting the ring gaps. Race engines are sometimes rebuilt several times per race season. They would start with a known safe number on the top ring gap and with every tear down they would tighten the ring gap by .001 or less and record that information. At some point on tear down they would find witness marks of the ring starting to touch or close the gap under high heat/hard acceleration. On this tear down they would open that ring gap by a 1/2. or .0005. a half thousanth. Now they had the perfect ring gap for max power in the engine. At this point they made the best power with the least amount of blow by. Serious racers can play this game but for us normal folks you build the engine using KNOWN safe ring gaps for the best performance without ever butting the rings in operation.
Reasons rings don't seal.
- Bad bore finish, Rings need a good cross hatch, the cross hatch controls the amount of oil on the cylinder wall and the speed at which the ring spins while running. You want a slow spinning ring while you run, it drags oil accross the ring face and maintains a better ring seal. Too steep of hone finish maybe 70* angle and the rings spin fast, don't seal well and wear the ring lands in the pistons. Too flat of a cross hatch and the rings spin slow so they don't drag oil and don't seal well. What is to flat, maybe 25* can do this. Most modern engines use a cross hatch angle of 45 to 60*. It does vary by application and operating RPM. So a Corvette engine revving 7,000 RPM might have a different cross hatch angle than a Duramax with a max RPM of 4,000. The amount of oil necessary to lubricate the piston also varies by engine design. Hard working low RPM engines need more oil on the bore than a high speed low torque engine. Deeper grooves in the cross hatch hold more oil than shallow groves in the cross hatch. All things to consider when building your engine.
- Bad Hone, same as bad bore finish but in this case if the operator does not use enough pressure on the hone while it works or if the honing fluid is really dirty and overdue for a change the cross hatch looks good but under a microscope you can see the grooves are deeper in one direction than the other. I forget which cuts deeper but the cross hatch on the up and down stroke are not the same and it leaves a finish that makes the rings spin fast which promote ring wear and give a lousy ring seal. Using the wrong stone in the hone can cause bad blow by also. Hard cylinder walls need to be cut with a unique stone, use the wrong one and the cross hatch will be bad.
- Too Rough of a hone For many years machine shops thought you needed a rough bore finish to break in your rings. This is very old advice and went out of school about 1980. Since 1980 rings have started lasting longer and longer, some go 1 million miles today without blowby or oil consumption. They seal on a very smooth surface compared to the 1980 finish.

The days of using a hand hone or a ball hone to rebuild an engine are long gone. (40 years long gone) You must use modern tools with a good hone operator to get OEM type long life piston ring wear and performance.
i apprecaite some of the tech you have here but its too generalized for the application. A .0223 top ring gap and a .005 piston to wall clearance (even on cast pistons) will NOT cause the issues hes seeing with a broke in engine. compression will be in the 360ish range with blow by but it damn sure wont do what his is. why? because thats how guys built these engines back in the 2000's using stock lb7 pistons and just honing the block (stock bore). typically for a 600hp and up engine, top ring gap was .022 and second was .024. That is just a typical 600, not nitrous setup.

hone angle and finish can play a part but we are talking a MAJOR amount of blow by. ive seen and worked on badly finished blocks and this would take the cake if that was the case. it would have to be absolutely terrible.

in this situation, it far more likely the bore is wrong, oil control rings are broke from assembly (very easy to do), or rings are way off.


Either way, this engine needs to come out and be torn down. plain and simple.
 

West

New member
May 18, 2022
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3
Folsom CA
You are correct, if all 8 cylidiners are down from 360 compression to 275 something is assembled or prepared wrong.
Dose the Duramax use a Keystone top ring or traditional top ring? I could look it up but a Keystone does not have a top and bottom so it cant be reversed while a traditional ring is affected by compression to help it seal and can be installed upside down. You guys that know the duramax will know this I am sure.
 
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715Hunter

Member
Jul 28, 2022
73
12
8
Missouri
na, this isnt a flash rust issue. this is a bad machining issue. balance rates wont show anything because the power balance between cylinders is good. When you look at balance rates, you need to look at the main injection flow rate as well, thats how much fuel overall is being used. a healthy engine and injection system will have a main rate around 8-9mm3.

with compression that low, im not surprised at your issues. that is BAD. gotta tear that engine down and start micing things out.


i apprecaite some of the tech you have here but its too generalized for the application. A .0223 top ring gap and a .005 piston to wall clearance (even on cast pistons) will NOT cause the issues hes seeing with a broke in engine. compression will be in the 360ish range with blow by but it damn sure wont do what his is. why? because thats how guys built these engines back in the 2000's using stock lb7 pistons and just honing the block (stock bore). typically for a 600hp and up engine, top ring gap was .022 and second was .024. That is just a typical 600, not nitrous setup.

hone angle and finish can play a part but we are talking a MAJOR amount of blow by. ive seen and worked on badly finished blocks and this would take the cake if that was the case. it would have to be absolutely terrible.

in this situation, it far more likely the bore is wrong, oil control rings are broke from assembly (very easy to do), or rings are way off.


Either way, this engine needs to come out and be torn down. plain and simple.
I talked to the shop today, and while I wasn't able to talk to the guy who builds them, they said he thinks that it's "normal, take 10-15k miles to break in."
I asked them for the piston to wall clearance and ring gap, so we'll see if I hear back from them.
What's weird is that they are a locally well-known shop that has built many engines across all makes, and have a stellar reputation.
 

715Hunter

Member
Jul 28, 2022
73
12
8
Missouri
You are correct, if all 8 cylidiners are down from 360 compression to 275 something is assembled or prepared wrong.
Dose the Duramax use a Keystone top ring or traditional top ring? I could look it up but a Keystone does not have a top and bottom so it cant be reversed while a traditional ring is affected by compression to help it seal and can be installed upside down. You guys that know the duramax will know this I am sure.
Thanks for the tech info.
 

Chevy1925

don't know sh!t about IFS
Staff member
Oct 21, 2009
21,106
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113
Phoenix Az
I talked to the shop today, and while I wasn't able to talk to the guy who builds them, they said he thinks that it's "normal, take 10-15k miles to break in."
I asked them for the piston to wall clearance and ring gap, so we'll see if I hear back from them.
What's weird is that they are a locally well-known shop that has built many engines across all makes, and have a stellar reputation.
full blown BS my man. ive built 1500hp capable engines and none of them have ever had that kind of blow by, even on first start up.