6.2 Broken Crankshaft Revisited.

[Westech]

When I have blown engines it has been at higher RPM and I have ALWAYS tossed a rod. I have never broken a crank at high RPMS only braking connecting rods.
I am thinking that lugging the engine would place WAY more stress on the crank then a high load and high RPMS.
When lugging the piston that fires is trying to push the crank around faster then it can move... IE a over pressure event.
It seams that the balancer may be a issue along with poor castings of the crank.
maintenance (oil changes coolant ect) will not have much effect on crank failures. Poor maintenance will cause bearing failures before a crank brake apart.
When a rod or main bearing fails you will hear it/feel it. it take a considerable amount of time after a bearing fails to cause catastrophic crank failure.

 

[dependable]

Only 6.2 CUCV crank failure I have seen in person was in a 1008 I sold to a fellow member. He did drive it at highway speeds once in a while, and his harmonic balancer was in bad shape at the time. He is a good mechanic and suspects the balancer was a major factor.

He said his truck also would still run, badly, with the crank broken. My two cents, as they say.

 

[rustystud]

The 6.2L engine was designed for GM by Detroit Deisel. It was one of Detroit Diesel's first steps into the 4-stroke market. You can tell that Detroit Diesel was kind of new to that game. Though the 6.2L is not what I would consider the worst diesel engine ever. I have to give that tittle to the 8.2L V8 that Detroit Diesel produced. These two engines do share some similarities, and faults.

OK, first off I don't know where your getting all this wrong information but Detroit Diesel has built 4 stroke engines for over 3 decades ! Yes they are known for their 2 stroke diesels but they made a inline 6 and 4 cylinder 4 stroke diesel engines since the 1980's and still make the 4 strokes today. As far as the heavier crankshafts being weaker then your inline engines would all be breaking shafts left and right ! ALL inline engines have a Larger crankshaft then a V8 or V6 engine. Have you ever rebuilt a diesel inline 6 or V8 engine before ? If you had then you would not say such things. Even gas inline engines have larger crankshafts then the V8 gas engine. Also who ever taught you that V8 engines have a third "axis" ? WHAT are you talking about ? There is NO cancellation of forces in any engine. There is only circular motion and the need to balance this from vibrating. If you cancelled the downward motion of the pistons and rods then you would not have and turning of the crankshaft and no forward motion of the vehicle ! Now your statement of a "Liquid" fuel being injected into the combustion chamber is totally wrong also. It is a vapor ! A vapor which is burning ! This would happen in "any" engine, gas or diesel. Granted in some engines like the Multifuel there is a bit of liquid fuel injected but again it is burning ! If according to you this "in-compressible" fuel would cause problems then what is happening to engines that will not start ? Or that take a while to start. Do they all get damaged by this fuel ? Of course not ! Before you post again why don't you take a few minutes and learn how a diesel engine actually works. Your statement of the "Injection" cycle gives it away that you really need to learn this.

 

[rustystud]

Now before anyone starts bashing me for being mean on my last post let me remind you all that this web site "Steel soldiers" is here for the military vehicle community to learn and share information on how to run and maintain our vehicles. It is not a site dedicated to "Fairy" stories about the magic "pixi" dust that makes all engines run. Rather it is "fact based" on knowledge of mechanics and real life stories of how this equipment runs and gets fixed. So when someone comes along spreading mis-information that really gets me angry ! Some guy seeking help for his truck will come to this site and see that post and not knowing better thinks that is the way things really work since Steel soldiers has a reputation for good honest answers. I'm not saying that if your not a mechanic you cannot post here, but what I am saying is that if you don't know how something works don't try and "make-up" some crazy story of how you think it should work just to make a post ! That is helping no one ! If you found something that really worked to fix a problem then by all means share it ! If you did something to make your truck better then share it ! If you have a story about your vehicle then share it ! But if you make up crap just to post here then I really hope that the membership here will jump on them like a ton of bricks ! That includes me ! I have made bad posts before and other members pointed it out and I corrected it. Some of my knowledge is getting a little long in the tooth and I might not be up on the latest technology. Hopefully this site will stand the test of time and in years to come when I am long gone people will still be able to come here and find the answers to their vehicles problems, without having to dig through a bunch of garbage information. So concludes this days rant.

 

[Two Stroke Madness]

OK, first off I don't know where your getting all this wrong information but Detroit Diesel has built 4 stroke engines for over 5 decades ! Yes they are known for their 2 stroke diesels but they made a inline 6 and 4 cylinder 4 stroke diesel engines since the 1960's and still make the 4 strokes today. As far as the heavier crankshafts being weaker then your inline engines would all be breaking shafts left and right ! ALL inline engines have a Larger crankshaft then a V8 or V6 engine. Have you ever rebuilt a diesel inline 6 or V8 engine before ? If you had then you would not say such things. Even gas inline engines have larger crankshafts then the V8 gas engine. Also who ever taught you that V8 engines have a third "axis" ? WHAT are you talking about ? There is NO cancellation of forces in any engine. There is only circular motion and the need to balance this from vibrating. If you cancelled the downward motion of the pistons and rods then you would not have and turning of the crankshaft and no forward motion of the vehicle ! Now your statement of a "Liquid" fuel being injected into the combustion chamber is totally wrong also. It is a vapor ! A vapor which is burning ! This would happen in "any" engine, gas or diesel. Granted in some engines like the Multifuel there is a bit of liquid fuel injected but again it is burning ! If according to you this "in-compressible" fuel would cause problems then what is happening to engines that will not start ? Or that take a while to start. Do they all get damaged by this fuel ? Of course not ! Before you post again why don't you take a few minutes and learn how a diesel engine actually works. Your statement of the "Injection" cycle gives it away that you really need to learn this.

For someone who is as in touch with diesels as you are you should have known that Detroit Diesel-Allison built it's first 4-stroke diesel in 1980. They had to buy the patent rights just to get into the 4-stroke market. Pancake engines are opposed piston engines. These engines are the most balanced engine you can get. They require almost no counterweight for balance. Now imagine that engine as two inline engine laying down sharing the same crank shaft. Now raise up the ends until you have created the V configuration. Great, but now you need to add counterweight to the crankshaft because the forces from the pistons and rods on the other side of the block are no longer canceling each other out. The inline engine has the same weight traveling in both directions. There are always two pistons reaching top dead center at the same time, one starting it's intake stroke, one starting it's power stroke. Inline engines typically have a larger bore than their V8 counterparts, and they are longer to accommodate for the fact that each cylinder has it's own main bearing. Any extra weight on the inline engines crankshaft is in the center, but per cubic inch the V8's still need more counterweight to stay balanced. If you don't believe what I said about fuel being in-compressible then take the injection lines off a diesel engine and you will notice how much faster that engine cranks over. This will have a greater affect on a higher compression engine. Liquids and vapors still share the same properties, and the diesel fuel actually burns quit slowly compared to the speed of the combustion cycle. You might be suprised to learn how long that vapor is present in the cylinder before it burns. I didn't say anything about damaging the engine, but if the crankshaft has a weak spot the injection cycle will be what breaks it. Think about what everyone else has been saying in this thread. They believe that lugging these engines is what is killing them, and they are most likely right. At slower speeds when your pushing the throttle down your injecting a greater amount of fuel into a cylinder that is flooded with exhaust gasses making the fuel burn at an even slower rate. To an extreme extent one could even have an engine hydro-lock under these circumstances. By the way, yes I have built a few high performance diesel and gas engines over the years so I do have a decent grasp on the mechanics. I'm not just a manual page turner, I build engines to perform outside their intended design criteria. Which means busting out the pen and paper and doing some physics. One more thing if you can find them I would really like to learn more about the 4-stroke engines that Detroit Diesel supposedly built prior to 1980. Models please.

 

[rustystud]

For someone who is as in touch with diesels as you are you should have known that Detroit Diesel-Allison built it's first 4-stroke diesel in 1980. They had to buy the patent rights just to get into the 4-stroke market. Pancake engines are opposed piston engines. These engines are the most balanced engine you can get. They require almost no counterweight for balance. Now imagine that engine as two inline engine laying down sharing the same crank shaft. Now raise up the ends until you have created the V configuration. Great, but now you need to add counterweight to the crankshaft because the forces from the pistons and rods on the other side of the block are no longer canceling each other out. The inline engine has the same weight traveling in both directions. There are always two pistons reaching top dead center at the same time, one starting it's intake stroke, one starting it's power stroke. Inline engines typically have a larger bore than their V8 counterparts, and they are longer to accommodate for the fact that each cylinder has it's own main bearing. Any extra weight on the inline engines crankshaft is in the center, but per cubic inch the V8's still need more counterweight to stay balanced. If you don't believe what I said about fuel being in-compressible then take the injection lines off a diesel engine and you will notice how much faster that engine cranks over. This will have a greater affect on a higher compression engine. Liquids and vapors still share the same properties, and the diesel fuel actually burns quit slowly compared to the speed of the combustion cycle. You might be suprised to learn how long that vapor is present in the cylinder before it burns. I didn't say anything about damaging the engine, but if the crankshaft has a weak spot the injection cycle will be what breaks it. Think about what everyone else has been saying in this thread. They believe that lugging these engines is what is killing them, and they are most likely right. At slower speeds when your pushing the throttle down your injecting a greater amount of fuel into a cylinder that is flooded with exhaust gasses making the fuel burn at an even slower rate. To an extreme extent one could even have an engine hydro-lock under these circumstances. By the way, yes I have built a few high performance diesel and gas engines over the years so I do have a decent grasp on the mechanics. I'm not just a manual page turner, I build engines to perform outside their intended design criteria. Which means busting out the pen and paper and doing some physics. One more thing if you can find them I would really like to learn more about the 4-stroke engines that Detroit Diesel supposedly built prior to 1980. Models please.

There are so many errors in your last post I don't know where to begin. The series 50 engine came out in 1987 after Penske bought the majority share of Detroit diesel. As far as Detroit having to pay for the rights to make a 4 stroke engine are you kidding me ! If there ever was a patent for the 4 stroke design that patent went out over 200 years ago ! I have never noticed a difference in the crank speed of any diesel engine that had the injection lines off. Again where are you getting this information ?
There is only one thing correct in your post and that is that Detroit Diesel never built a 4 stroke engine until the series 50 engine. ( I misspoke when I said 1960. Your crazy statements got me so rattled I couldn't think straight !) They helped in the design of the 6.2 GM diesel but did not make it.
So are you saying your a mechanic by trade since you have built engines ? If so then you missed some classes. There is 4 cycles to a 4 stroke engine and none of them is the "Injection" cycle. As far as what is breaking cranks it is well documented that the Harmonic Balancer and dual Flywheel and Accessory Drive balancer is what helped break the cranks.
As far as when the fuel is put into the combustion chamber that happens at 'Injection" so I know actually when it happens ! Again you show no knowledge of diesel engines at all !
So far all you have provided is hearsay. Nothing in writing. Until you provide this I cannot believe a word you have said.

 

[Two Stroke Madness]

1987 was not 50 Years ago, and diesel engines have been around for maybe 100 years. The patent was on the inline 6 cylinder design. Detroit Diesel was forced out of the 2-strokes by the EPA and needed a new engine design. No I do not build engines for a living just for a hobby. I never said that Detroit built the 6.2L, but said just as you did. Also the injection cycle just sounds better then saying when the injector squirts fuel in. Most of my info comes from what I have physically seen first hand or though my own personal experience.

 

[Two Stroke Madness]

Sorry, the diesel engine was invented in 1897. Had to look it up.

 

[rustystud]

1987 was not 50 Years ago, and diesel engines have been around for maybe 100 years. The patent was on the inline 6 cylinder design. Detroit Diesel was forced out of the 2-strokes by the EPA and needed a new engine design. No I do not build engines for a living just for a hobby. I never said that Detroit built the 6.2L, but said just as you did. Also the injection cycle just sounds better then saying when the injector squirts fuel in. Most of my info comes from what I have physically seen first hand or though my own personal experience.

I know 1987 was not 50 years ago, I said as much and the EPA had a lot to do with the death of the 2 stroke diesel but not everything. It was market share that drove Detroit to make the series 50 engine. As far as your post about removing the injection lines goes, since the engine is fighting the cylinders trying to fire off it would appear that the engine is running slower. It has nothing to do with fuel !
What do you do for a living then if your not a mechanic ?

 

[Two Stroke Madness]

By the way, does anyone remember what we were all talking about?

 

[rustystud]

By the way, does anyone remember what we were all talking about?

Yes, what do you do for a living.

 

[Two Stroke Madness]

I know 1987 was not 50 years ago, I said as much and the EPA had a lot to do with the death of the 2 stroke diesel but not everything. It was market share that drove Detroit to make the series 50 engine. As far as your post about removing the injection lines goes, since the engine is fighting the cylinders trying to fire off it would appear that the engine is running slower. It has nothing to do with fuel !
What do you do for a living then if your not a mechanic ?

I'm a carpenter/metal fabricator. I can build most anything out of wood or metal. I don't do mechanic work for a living because I like it. I don't think I would enjoy it as much if I had to do it for a living. I didn't want to call you out but turnabout is fair play. You seem like an intelligent sort. I think some of our arguments are just a matter of miscommunication.

 

[Cucvnut]

I'm good with that. Just didn't want the discussion to turn into. " I could had an inline 6"

Thats his MO, did the same thing to me in my post.

 

[rustystud]

I'm a carpenter/metal fabricator. I can build most anything out of wood or metal. I don't do mechanic work for a living because I like it. I don't think I would enjoy it as much if I had to do it for a living. I didn't want to call you out but turnabout is fair play. You seem like an intelligent sort. I think some of our arguments are just a matter of miscommunication.

Fair is fair. For over the last 35 years now I've been a "ASE Certified Master Mechanic" working in the Heavy Truck and Bus industry. When I was younger I was in the Marines for 4 years in Tanks then in Motor Transport as a mechanic and company welder. I worked as a welder-machinist for 10 years making equipment for the fishing industry. I have 4 years of college in mechanics (during my apprenticeship) and 1 year at trade school for mechanics. I have over 3 more years of training in modern Transmissions and Differentials and also Air-Conditioning and Fuel Injection systems. If you want I can take pictures of my certificates, but I will cover my name.
So I am not just speaking out my A$$ when I say that what your talking about doesn't make much sense. I have stated earlier that I don't want this web site to lose it's credibility when it comes to military vehicles. So when someone says something that is just "not right" I will say something. I'm not trying to bust your butt, I just want you to post responsibly and if need be to document what your saying. I just retired this year and I'm sure there will be things coming up that I will not know about. But if I don't know about it I will ask to see the documents from whoever is posting the information.

 

[Two Stroke Madness]

I can respect your experience and would like to learn as much as you know. Unfortunately I have no physical documentation to prove what I say. Like I said it's just personal experience and what I have been told by the people in the know. I'm like you I just want the right answers that's why I thought my posts might be of some value here.

 

[Two Stroke Madness]

Thats his MO, did the same thing to me in my post.

Hey, I owned up to that. I didn't mean for that post to come off the way you took it.

 

[rustystud]

I can respect your experience and would like to learn as much as you know. Unfortunately I have no physical documentation to prove what I say. Like I said it's just personal experience and what I have been told by the people in the know. I'm like you I just want the right answers that's why I thought my posts might be of some value here.

That's OK. Where all free to say what we want here as long as you don't say "This is the truth" if you don't have documentation to back it up. If you do that you WILL get called out on it. If you say "I have an opinion" that's fine and people can discuss it. We don't want this site becoming some "junk" site that has total garbage all over the place like the site my son went to which said the "Holocaust" never happened. It was just a smear campaign against the Nazi party and Hitler. That is a total junk site ! Of course I told my son that is total garbage and then showed him a newsreel showing the US military liberating a concentration camp.

 

[Two Stroke Madness]

I hate fear mongering of any kind, and I try not to do it. I guess the only thing I can give you now is an example. You would think the designers of the biggest and most expensive diesel engines in the world would want to design the most simple and efficient engines that they possibly could. Those diesel engines are always inline 2-stroke engines. Pound for pound the inline 2-stroke can deliver the highest efficiency of any diesel engine. Maybe not the highest level of longevity though.

 

[Two Stroke Madness]

I suppose we should get back to the 6.2L discussion. The nice thing GM did for you guys was they made a ton of those engines. So even if you have a problem with one you can cheaply replace it with another zero mileage rebuild. If I was ever going to buy another military 5/4 (which I don't plan on) I would buy the truck and buy a rebuilt engine at the same time. I've seen those engines sell for as little as $200 for a zero hour rebuild.

 

[Tinstar]

Ok, I'm gonna ask a stupid question.

What is "Lugging"?

I think I know but have to ask.