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Hey guys! new to the forum, been on diesel bombers hoping for more activity here lol!
So long story short my ole' reliable 96 12v developed a significant tick/knock while pulling my not so heavy boat up a grade. coolant at 170 20psi boost 1100 egt and out of the blue a small noise became loud by the top of the hill . When I stopped, the engine stalled and felt as though it was trying to seize. hopped out checked the fluids, all looked well, and then she reluctantly started up again, when i hopped back out my 180k engine now had a lot of blowby that was not present before. ffrom this point on the motor had a consistant knock that fluctuated with rpm and did not change much with load. I limped her home about 30 miles, parked for about 6 months, drove her another 10 miles to my shop. dropped the NV hoping my clutch pack had busted somthing and was making the noise but no luck. Then I pulled the engine. Made a side mount out of some 3/8 plate, got it on the stand, pulled the head and my suspicion was verified. cylinder six was the issue, the piston skirt has scraped away my beautiful crosshatching from the sides perpendicular to the crank. dropped the pan and pulled the piston today. The lower compression ring is seized in its groove and seems to be the root of the problem. the piston took more damage than the cylinder luckily. So far I have only taken some quick measurements but its looking like I could get away with a new piston, rings and a good hone. all the bores are near 4.016 and the wear on cylinder 6 is less than .001 out of round. you can barely feel the scratches. I had already planned on pulling the engine to reseal and build her up for a hopefully reliable 500hp daily driver, So my current dilemma is how far I should go on the short block. I'm leaning towards just honing and replacing one piston and mains/rod bearings and oil pump, I considered replacing all the rings but i'm not sure it would be worth the risk of them not seating. Im definitely going to get the block and head checked at the machine shop for bore, out of round, taper, warpage etc, but assuming everything is within spec i'm leaning towards saving the money and not doing a full rebuild. I'd appreciate any advice or thoughts you guys have at this point, there is certainly more to come but I plan on getting the bottom end squared away first.
will have some good pics up soon apparently i need to have more posts first
 

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Honestly at 180k on the odometer I seriously doubt the other 5 cylinders have bad rings. The rear cylinder gets the coolant flow last so #6 has a tendency to swell and seize long before the rest do. Typically a performance build has a few thousandths more piston to wall clearance on #6 to compensate for the fact that it runs hotter. So basically honing that cylinder and running it looser will result in a more equal piston to wall clearance among all six cylinders under heavy load than the factory setup would anyways. So if you are trying to keep the cost down I truly don't see leaving the other cylinders alone as a mistake. I would feel more comfortable with that than doing a rebuild with cheaper non OEM parts trying to keep your budget in line.

I am a fan of a coolant bypass at the rear of the block to help move the coolant and relieve pressure at the back of the block at higher rpms.
 

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There's 1 types of coolant bypass 1 for pressure for high RPM and the other for temperature which is for towing maybe???

Not sure how this works because the coolant temperature sender is right there how would it get hot unnoticed ?
 

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#6 gets hot far quicker than the gauge is able to respond.

I think the issues on #6 not only have to do with poor coolant flow but also it's a cylinder that runs at the hottest piston temp due to poor airflow compared to the other 5.

Piston temp is probably why the ring failed I suspect?
 

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How "turned up" was your engine, OP? How do some guys have a million miles before a rebuild, and some fail under 200k miles?
 

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Discussion Starter #9
The bypass sounds like a good idea, although i was under the impression that it was more of an egt issue is cylinder 6 along with coolant temp. crazy part is my truck has always ran cool like 170-180 unless i was towing really heavy. What do you guys think about whether or not to replace rings and hone the other 5? I plan on getting oem rod and main bearings and oil pump. Another thought is I could get number 6 bored out just a hair if it will help my odds in the future lol. I do plan on pushing her a lot harfer after this is all taken care of. And Spawn, all mods are in my sig, truck was close to stock and it wasnt pushed hard at all as my clutch would slip at about 25psi boost
 

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I would agree to just give it a home and clean up the other cylinders. See what your machinst says.

You can address the air flow issues on #1 and #6 in the head if you want that will help mitigate the problem.

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Number 6 runs hot due to it being the last cylinder to get coolant and the other 5 have already heated the coolant up, it's the nature of a inline engine. It's normally not noticed until more fueling is added and their loaded for extended periods.
Years ago we had the same issue with the 401 engine on 8000 Ford tractors.
They ran fine from the factory, but if you turned the fuel up a little for more power it would score #6 piston.
The simple fix was to hone that cylinder .003 over giving more room for piston expansion.
When I rebuilt my present engine I had an extra .003 honed into #6 cylinder.
Towing heavy with my fueling mods I knew #6 was going to heat up.

OP make sure to check the piston cooling nozzles, their a big part of keeping the pistons cooled on these engines.
 

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Hemirunner, aderss the airflow would be a more spread out dual intake? I will definitely get the machinist's opinion. Destroked, I will be sure to check the cooling nozzles as well, the loose bore idea for cylinder might just save my a** haha. Any thought on whether or not to put new rings in all the cylinders?
 

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I'm not a fan of having an entire motor apart, just to slap in the the same old personally. That's halfassing it in my opinion, but it's not my truck. That being said, if you're about to drop money to make a DD 500hp truck, then a new set of rings and pistons for all 6 shouldn't be much of an issue, besides at the end of the day, all the little cost things like hoses, belts, coolant etc etc, add up quickly. It's way easier to justify dropping more money on new rings and pistons as a big purchase.

I highly highly highly suggest balancing the rotating assembly. I didn't do it with mine, and while my truck isn't incredibly rough at idle or anything like that, it would have just been some peace of mind to do so. The coolant bypass is about the only other thing I'm bummed I didn't do while the engine was out of the truck. I know I can do it while the engine is in, but getting to that rear freezeplug just isn't fun no matter how you paint it. Definitely gonna sub to this thread man.
 
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Hemirunner, aderss the airflow would be a more spread out dual intake? I will definitely get the machinist's opinion. Destroked, I will be sure to check the cooling nozzles as well, the loose bore idea for cylinder might just save my a** haha. Any thought on whether or not to put new rings in all the cylinders?
It will help, but marginally. The problem lies in the head casting. #1 and #6 ports do not flow the same as the rest of them. These cylinders are starved for air and are the typical failure points on an otherwise healthy engine when turned up and worked hard.

I'm not sure how far a stock head can be ported to flow the same across all 6 ports. That is something your machinist can answer for you once he takes a look at your head and gets some flow numbers.

Hamilton Cams just introduced a new head that solves this problem with room to grow. This head also is suppose to flow significantly more over stock. I just bought one and we will be taking it to get flowed soon.
 

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The head flow is only part of the problem. If you research single cylinder's seizing or scoring in an otherwise healthy engine on a 12v, roughly 75% of the time #6 is the failure point. CR are different because of the nature of injector failures dumping fuel and overheating one cylinder on those engines. #1 and #6 have almost identical airflow but #1 is rarely the first to go.

When I was building my ls1 procharged camaro there was a rash of #7 and #8 cylinder failures on forced induction or nitrous LS6 motors. As it turns out the LS6 motor had deleted the rear coolant vent ports on the cylinder heads. These two ports were directly above cylinders #7 and #8 and helped coolant flow and prevented air pockets in the rear of the cylinder heads. The LS1 motors had the coolant vent ports at all 4 corners of the engine and did not have rear cylinder failures like the LS6 motors. Soon many people started using the 4 corner LS1 coolant vent system and the rear cylinders failures numbers plummeted. Point being this type of problem is more common than most people think, and across far more engine platforms than people think.
 
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I'm not a fan of having an entire motor apart, just to slap in the the same old personally. That's halfassing it in my opinion, but it's not my truck. That being said, if you're about to drop money to make a DD 500hp truck, then a new set of rings and pistons for all 6 shouldn't be much of an issue, besides at the end of the day, all the little cost things like hoses, belts, coolant etc etc, add up quickly. It's way easier to justify dropping more money on new rings and pistons as a big purchase.

I highly highly highly suggest balancing the rotating assembly. I didn't do it with mine, and while my truck isn't incredibly rough at idle or anything like that, it would have just been some peace of mind to do so. The coolant bypass is about the only other thing I'm bummed I didn't do while the engine was out of the truck. I know I can do it while the engine is in, but getting to that rear freezeplug just isn't fun no matter how you paint it. Definitely gonna sub to this thread man.
I'm surprised your the first to tell me not to half it, my thought is that presumably this engine has at last another solid 200k if this hadnt happened, and i'm not totally convinced that new pistons and rings would outlive my factory ones by much if any. I could be wrong but it at least isnt seeming like I'd get a lot of bang for those bucks. zero blowby before this happened and strong compression. Assuming the rebuild went perfectly and the rings all seat nice all I would have really gained is a slightly tighter tolerance? Hell if i get another strong 200k and pull it out again I wouldnt be upset.

It will help, but marginally. The problem lies in the head casting. #1 and #6 ports do not flow the same as the rest of them. These cylinders are starved for air and are the typical failure points on an otherwise healthy engine when turned up and worked hard.

I'm not sure how far a stock head can be ported to flow the same across all 6 ports. That is something your machinist can answer for you once he takes a look at your head and gets some flow numbers.

Hamilton Cams just introduced a new head that solves this problem with room to grow. This head also is suppose to flow significantly more over stock. I just bought one and we will be taking it to get flowed soon.
If will definitely see how far I can go with some porting, seems like with cylinder 6 a bit looser, porting, intake and the bypass I should at least be in better shape! You think a cam helps keep these cylinders cooler? I have heard benefits are minimal on mild builds but I doubt it would hurt.

The head flow is only part of the problem. If you research single cylinder's seizing or scoring in an otherwise healthy engine on a 12v, roughly 75% of the time #6 is the failure point. CR are different because of the nature of injector failures dumping fuel and overheating one cylinder on those engines. #1 and #6 have almost identical airflow but #1 is rarely the first to go.

When I was building my ls1 procharged camaro there was a rash of #7 and #8 cylinder failures on forced induction or nitrous LS6 motors. As it turns out the LS6 motor had deleted the rear coolant vent ports on the cylinder heads. These two ports were directly above cylinders #7 and #8 and helped coolant flow and prevented air pockets in the rear of the cylinder heads. The LS1 motors had the coolant vent ports at all 4 corners of the engine and did not have rear cylinder failures like the LS6 motors. Soon many people started using the 4 corner LS1 coolant vent system and the rear cylinders failures numbers plummeted. Point being this type of problem is more common than most people think, and across far more engine platforms than people think.
So overall head flow combined with the coolant bypass and looser tolerance would be the best solution? seems sensible that this happens on all sort of engines. I have seen a few 6.0 vortecs that the back passenger cylinder goes dead before 200k!
 

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Many guys that are still running 12v's are pretty tight on cash and we tend to give advice based both on good practice and good budgeting. We won't judge if you if you say an all out rebuild isn't in the cards. That is what you're seeing with the advice given so far.

pretty much any machine shop that builds Cummins will ask if you're going to hot rod it and then take the rear cylinder out a few thousandths more. Standard procedure on these really. They will also taper the Piston tops so they don't expand the crown of the Piston and stick the Piston under extreme egts
 

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Ehhh I dunno man. Sure, you can take it and run with the old rings, but it's not like you can't buy new OEM replacement parts for it, and at the cost of only a few hundred dollars too. Besides that, I have a sneaking suspicion the the OEM pistons were subcontracted out to Mahle in the first place. Gmanss is right now, if you're tight on cash you could get away with it, but assuming that you want to go to 500hp I wouldn't see "tight on cash" as much of an issue.

Just my $0.02
 

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Truth...tight on cash and going for 500hp doesn't go hand in hand. There are a lot of young dreamers here though, lol. Mahle does a lot of OEM pistons including Cummins parts. A kit from Enterprise engine isn't too crazy price wise. I would stay with Mahle and Clevite for parts. Interstate McBee can be hit or miss for performance builds.

If you like the truck and plan to keep it the peace of mind knowing you have a fresh engine is worth the price of admission.
 

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Full rebuild certainly isn't out of the question I just want to get a good return on the money spent. If I were to go with new pistons and rings, would you recommend going .020 over or std and hone? I have also heard some horror stories about rings not seating and want to avoid that at all costs. Do you guys think if i were to go the cheap route I would just be looking at a shorter life before blow by and compression loss? Or would I somehow be asking for a huge failure? I get that new is peace of mind but the tolerances are what seem to matter most to me.
 
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