The Green Grendel

[campfire]

All those extra parts you have you can sell, make a couple bucks back.

Hmm , where the crank broke has me curious as most break close to the front of the block. Mine broke just after the number 2 main. I wonder if your flywheel is slightly out of balance. Or like you said, just a poor casting that finally gave up.

Their surprisingly stout little engines, once you take care of a couple little things as your finding out.

Try titling your engine with the vacuum pump out, it might be hitting the firewall.

This forum has me convinced that I'm the very last person out there still willingly running a N/A 6.2 engine.
Entire engines run $300, so I don't think I'll get much for the parts. Do you want anything? The new engine was complete aside from accessories and the IP itself.

I never replaced the harmonic balancer. It wasn't visibly loose, but it wasn't new. The last 500 miles or so I have felt a small crank-speed vibration through the clutch pedal whenever I pressed it lightly. It was just enough to raise a flag, but I couldn't pinpoint it. Then I got a small amount of tapping during engine warmup. This was probably an exhaust leak, though it disappeared fast enough I didn't get it properly diagnosed. But I changed the oil just in case it was getting too sludgy to pump cold. It made no difference. When the engine blew up it still had the slight vibe. I'm thinking the balancer stopped balancing.

As for now, I put the same flywheel and clutch on the new engine. The flywheel does have scraping on the back side, where it hit the block. Also, there is now a little bit of play in the transmission input shaft. When I did the swap I was told every transmission input shaft wiggles, but mine was tight. Now it's back to being normal. And the input shaft nose has a couple lathe marks in it now. But minor scratches aside, it all looks fine. It was on there for the entire 5000 miles that I've been driving the truck, and I don't see how the balance would have changed during that time.

The new engine came with a flywheel, but I thought sticking with the known flat surface was better than finding out the other one is warped. I don't think anyone in town has the ability to resurface a flywheel.

The vacuum pump is just sitting in the hole, it's already rotated so it's facing forwards instead of backwards (intake is out). But I'll double check it just in case.

 

[campfire]

Speaking of extra parts, I'm looking for a dual throttle cable bracket to hook up cruise control.

For a 6.2 injection pump? I don't have one, as the bracket bolts to the pump (which I didn't get). Oddly enough, I have some form of aftermarket cruise control solenoid in that pile, but no bracket to attach it to.

 

[AgDieseler]

This thing is obese...

“Big boned”

Very revealing deconstruction, and a unique break for sure. I agree that it had likely been failing for some time - a small crack leading to a larger one.

I would submit that your crank was weakened from factory condition and prone to failure. Note the marking that the mains and rods were both turned .010/.010, eliminating the factory nitro-hardening, which only penetrates to .005 or so. What’s under that is soft ductile nodular iron, and very susceptible to failure without the hardened bearing surface.



Up side - hopefully the new long block has an original crank, and you should have good confidence in that. Also, cool parts on your “sacrifices to the gods of Diesel” shelf.

David

 

[campfire]

“Big boned”

 

[campfire]

Very revealing deconstruction, and a unique break for sure. I agree that it had likely been failing for some time - a small crack leading to a larger one.

I would submit that your crank was weakened from factory condition and prone to failure. Note the marking that the mains and rods were both turned .010/.010, eliminating the factory nitro-hardening, which only penetrates to .005 or so. What’s under that is soft ductile nodular iron, and very susceptible to failure without the hardened bearing surface.

View attachment 274667

Interesting. I figured the engine had been reworked, as all the caps were stamped with numbers (in reverse order of the con-rods, not the actual cylinder number). So the frontmost piston that I removed is marked as "8." But I didn't put 2 & 2 together regarding the .010/.010 stamping, nor did I realize this crank was originally nitro hardened. But it does make sense.

Up side - hopefully the new long block has an original crank, and you should have good confidence in that.

The new engine had no stampings on the rotating assembly.

 

[campfire]

Also, cool parts on your “sacrifices to the gods of Diesel” shelf.

I hafta keep some sort of momento, eh?

 

[AgDieseler]

I hafta keep some sort of momento, eh?

Of course! I still have a bent rod hanging on my wall.

The new engine had no stampings on the rotating assembly.

A great sign. What do the bearings look like?

Nitro-hardening was one of GM’s ways to use a cheaper nodular cast crank but maintain operational durability. If one can’t polish their factory crank, it just has to be replaced. If you have a 6.5 or one-piece rear main 6.2, the Scat crank is really nice.

David

 

[campfire]

Of course! I still have a bent rod hanging on my wall.

 

[campfire]

A great sign. What do the bearings look like?

I only pulled the one cap needed to change the rear main. That bearing looked perfect to these novice eyes. There was salt corrosion on the exhaust & oil pan, but the rest of it looked very clean inside and out. The rear main was still rope packing, so the "40,000 miles out of a county plow truck" story might not just be sales talk. Didn't spot any cracked webs, either.

 

[campfire]

If you have a 6.5 or one-piece rear main 6.2, the Scat crank is really nice.

If.

You know what's even nicer than the Scat crank? Having a one-piece seal.

 

[Blue85]

View attachment 274657

I think I see the problem...

Broken like it is explains why the 2 parts of the crank still had to turn together (and it ran) - with a horrendous clatter, and why you picked up endplay in the back. Think what could have happened if you continued driving it. Either that section (and other stuff rubbing) would create enough debris to cause a second failure, or it would eventually separate and then come back together again in total catastrophe.

Isn't a disassembled 6.2 worth like $75 in scrap?

 

[campfire]

Broken like it is explains why the 2 parts of the crank still had to turn together (and it ran) - with a horrendous clatter, and why you picked up endplay in the back.

Yeah, there were metal shavings and glitter all over the oil pan. I wiped it down for quite a while before putting it on the new engine.

Think what could have happened if you continued driving it. Either that section (and other stuff rubbing) would create enough debris to cause a second failure, or it would eventually separate and then come back together again in total catastrophe.

It ran for no more than 10 seconds total after the break. I'm sure it would have continued wrecking stuff. I shut it off because I didn't want the crank to break. But knowing what I know now, the transmission input shaft is what really got saved by that decision. It had just started lathing the block and the aluminum cone on the starter motor.

Isn't a disassembled 6.2 worth like $75 in scrap?

Not sure. Give me a few days and I'll be able to tell you. I did need to remove the aluminum timing cover to get the crank out. But I'd bet it's less than $75, unless scrap price is up.

 

[diesel4me]

It's a sin GM didn't spend the extra $10 to forge a crank, rather than use cast crap ones that break...not that the 6.2 is a "great" diesel,but they would probably go 500,000 miles if not for the cranks breaking..

I dont buy the bad harmonic balancer theory either,I've seen several break the cranks with perfectly fine harmonic balancers ,including the '87 C code one I got for parts out of my friends C-30 ramp truck..

I've read the cranks in 6.2's are surface hardened,and shouldn't be turned undersized,you do lose the hard wear surface,and those cranks are weak enough to start with..

I had to snicker when I read the part where you said "I never heard any rod knocks"...how could you tell,a 6.2 running good sounds like it has 8 spun rod bearings!....
Some days mine clatters a lot,and once in a while it'll get a lot quieter,almost silent...but it always goes back to being noisy again..might be air in the fuel lines or pressure related..

Mine also "ticks" after a cold start too most of the time,ever since I had a glow plug break and get chomped up in the #3 cylinder--I hope its due to a bent push rod or a lifter that needs to pump up,not a crack starting in the crank...

 

[campfire]

I had to snicker when I read the part where you said "I never heard any rod knocks"...how could you tell,a 6.2 running good sounds like it has 8 spun rod bearings!....

I always expected the oil starvation episode to be the ultimate downfall of this engine. But looking through the ruins I don't think that was the case. I think David is probably on the right path.

 

[diesel4me]

For a 6.2 injection pump? I don't have one, as the bracket bolts to the pump (which I didn't get). Oddly enough, I have some form of aftermarket cruise control solenoid in that pile, but no bracket to attach it to.

I think I have that factory cruise control pod bracket--my pickup came with a salvage yard engine,and it had cruise control evidently,but there was no vacuum pod or other parts for the cruise left other than the bracket itself on it..
I removed it because it was in the way,and I had no need for it..

 

[imiceman44]

This forum has me convinced that I'm the very last person out there still willingly running a N/A 6.2 engine.
Entire engines run $300, so I don't think I'll get much for the parts. Do you want anything? The new engine was complete aside from accessories and the IP itself.

I never replaced the harmonic balancer. It wasn't visibly loose, but it wasn't new. The last 500 miles or so I have felt a small crank-speed vibration through the clutch pedal whenever I pressed it lightly. It was just enough to raise a flag, but I couldn't pinpoint it. Then I got a small amount of tapping during engine warmup. This was probably an exhaust leak, though it disappeared fast enough I didn't get it properly diagnosed. But I changed the oil just in case it was getting too sludgy to pump cold. It made no difference. When the engine blew up it still had the slight vibe. I'm thinking the balancer stopped balancing.

As for now, I put the same flywheel and clutch on the new engine. The flywheel does have scraping on the back side, where it hit the block. Also, there is now a little bit of play in the transmission input shaft. When I did the swap I was told every transmission input shaft wiggles, but mine was tight. Now it's back to being normal. And the input shaft nose has a couple lathe marks in it now. But minor scratches aside, it all looks fine. It was on there for the entire 5000 miles that I've been driving the truck, and I don't see how the balance would have changed during that time.

The new engine came with a flywheel, but I thought sticking with the known flat surface was better than finding out the other one is warped. I don't think anyone in town has the ability to resurface a flywheel.

The vacuum pump is just sitting in the hole, it's already rotated so it's facing forwards instead of backwards (intake is out). But I'll double check it just in case.

Not true.
I have a suburban with a dead 6.2 and getting ready to put another in it.
And I have a shed full of 6.2 engines that I got for $300-500

 

[imiceman44]

Yeah, there were metal shavings and glitter all over the oil pan. I wiped it down for quite a while before putting it on the new engine.



It ran for no more than 10 seconds total after the break. I'm sure it would have continued wrecking stuff. I shut it off because I didn't want the crank to break. But knowing what I know now, the transmission input shaft is what really got saved by that decision. It had just started lathing the block and the aluminum cone on the starter motor.



Not sure. Give me a few days and I'll be able to tell you. I did need to remove the aluminum timing cover to get the crank out. But I'd bet it's less than $75, unless scrap price is up.

My 12 litre CAT engine got me $65.
I think a 6.2 will be closer to $30

 

[imiceman44]

Of course! I still have a bent rod hanging on my wall.

A great sign. What do the bearings look like?

Nitro-hardening was one of GM’s ways to use a cheaper nodular cast crank but maintain operational durability. If one can’t polish their factory crank, it just has to be replaced. If you have a 6.5 or one-piece rear main 6.2, the Scat crank is really nice.

David

I have a 599 block still a 6.2 and with the crank.
You are saying that crank is better than the older ones?

 

[AgDieseler]

I have a 599 block still a 6.2 and with the crank.
You are saying that crank is better than the older ones?

No. All 6.2/6.5 cranks are post-hardened cast nodular iron. The 599 block should be a one piece rear main, which means you can use the Scat crank. It’s a good piece of gear.

David

 

[imiceman44]

No. All 6.2/6.5 cranks are post-hardened cast nodular iron. The 599 block should be a one piece rear main, which means you can use the Scat crank. It’s a good piece of gear.

David

So scat as in aftermarket