another cracker

[Patrick m.]

Well it seems my 6.5L has joined the ranks of the cracked.
Tuesday morning at a modest 45 mph headed to work, i noticed the ominous white cloud behind me. No warning, no indication at all. At the next red light it started to miss (dropping a cylinder). After i arrived at work (it was only 7 more minutes) i shut the engine off, raised the hood as we all would and found coolant being pushed out of the reservoir. as i went to re-start it, it was hydro-locked, and hit pretty hard. Put 2 and 2 together....out comes the engine.
All of this, and i have never had any cooling problems, even before the cooling upgrade it allways ran at 210 and under.
Anyway, head gasket was blown at #2 cylinder, pulled the pan to remove the piston to check it for damage, and there it is, a big fat crack. From the outboard main bolt, headed straight for the cylinder (#2).
What to do.

[TAG]

I wonder how many of these blocks have cracked from this scenario. Maybe broken cranks also. If one cylinder fires before it hydrolocks i would guess something has to give.

[john8662]

Sad to hear that the engine finally went. You sure did get your money's worth though!

Guess you'll want to join the splayed main gang?

[Patrick m.]

At 210,000 miles, even a modest replacement engine will cost more than the truck is worth. So at this point it is either all or nothing.
I dont think i want a newer truck for the money they cost.
i do have a used block that is not cracked but is is a 506 block.
what do you guys think about using this 506?

[john8662]

Not a big fan of the '506 block. What you'll need to find out is the manufacture date on the block. The ones made from 97-98 were junk, because they had the larger oil spray piston coolers. IIRC, the later blocks had smaller spray holes/nozzles to combat the cracking situation.

Since your truck is a '95, find a 599 or 929 block.

I hear you loud and clear on not wanting a new truck. It's just too expensive, unless you're getting a HUGE cost of living raise, I know I'm not...

[ronniejoe]

I used a later 506 block for my project. The splayed mains will make it safe. I would highly recommend the oil spray system for piston cooling!

[Patrick m.]

At 209,899 miles my pistons looked great! The problem is they are loose in the cylinder.
the rings have pits in them! At least the top one does. Ths guy at the machine shop looked at this pitting with a puzuled face. (this machine shop has done at least 10 engines for our shop, with out one problem). They also do alot of diesel work, our shop does not. We tend to just do engine performance work on diesels, not overhauls.
So i have very much confidence in them.
Ronnie, did you see any pitting?
GMCTD? you guys have both been through this. I have a spare short block

This 506 block i am told came out of a 99 model van. Hence the reason to plug the center mount turbo feed and return.
There is a national guard base nearby, the machine shop says they do alot of work for them, and all of the blocks with the bosses in the rear of the block are good. All of the blocks with nothing in the rear are cracked!
My 929 block was cracked, and has nothing in the rear!
I am going to go 18:1 ( the block only needs .020 over. My crank needs NOTHING! I saw the measurement, all the way around over 200k miles its good..... with a timming chain! no gear drive!
18:1 with NEW heads cast in the USA, thicker deck surface, larger intake runners thanks to some work by the machine shop, larger exhaust runners for the same reason. Splayed mains thier way, which means welding up the existing outer main bolt hole, and cap, and re-drilling the entire path as a unit.
with a larger stud. All of this with MAHLE pistons, rings, brgs and Melling oil pump.
5 year waranty (no mileage). eventhough they know i will hit 20 psi boost!

All for a mere $3850 ( which includes a new 5521 Injection pump)
But it will take about three weeks to complete.





And yes, if this block cracks, they will get another block, and perform all the nec work to use the new block.

[ronniejoe]

I made a comment in post #34 of this thread (http://thedieselpageforums.com/tdpforum/showthread.php?t=4312&page=4&highlight=news) that the rings had plating peeling off. Kent also commented on that earlier in the thread. It looks like I never did post any pictures as I said I would. I don't have the rings around anymore.

Is your splayed cap method using the stock cap? It sorta sounded like it from the description you gave.

[gmctd]

How much 'ridge' did the cylinders have at 209kmi, Patrick (trick question)?

I agree with ronniejoe - if that 506 block has no cracks, splayed mains like JK's should hold it together.

Local heating\cooling stress in the webbing from the welding operations - I don't know.
Look at the deep undercutting of the mains webbing from the cylinder boring operations - scary stuff - to get a sense of why.

[john8662]

Dang, I had some empathy for ya, now I've got some sympathy for ya.

I was pulling the pan on a ~60k 6.2 to install a modified pan on the engine with an oil drain bung welded to it for a turbo when I (being nosy) was looking for cracks before throwing the used stud girdle in it (before putting it back into another truck). Was pretty happy cleaning the webs before I got to web #4 and saw a little ugly thing on just one side. Guess this would have been one of those cracked all up engines when normally pulled late down the road.

Oh well, I was gonna abuse it anyways...

J

[JeepSJ]

...all of the blocks with the bosses in the rear of the block are good. All of the blocks with nothing in the rear are cracked!


What is this boss of which you speak? A mounting boss for something?

[john8662]

The "boss" in the back is what is used to mount the center mounted turbo that the Hummers and G-vans use. The Boss has mounting places as well as a place to get oil psi and oil drain. Some blocks are drilled out to accept the turbo fittings, some are not and just have the casted material there...

[ronniejoe]

My 506 block had the boss and cracked in the second main web. Here's a picture:

http://www.schoolcraftpowertrain.com/Pictures_&_Data/IM000787.JPG

[JeepSJ]

Is that the flat spot next to the oil pump drive hole?

[Patrick m.]

that is the spot. I have now seen two different types of 506 blocks, those that have the holes drilled, those that dont.
work and searching continues. I found a source for aftermarket heads with a thicker deck surface to fight the cracking in the heads, the guy claims they are cast in the USA, and are fantastic quality. He also claims he has several engine re-man companies that buy his heads and have had no head issues.

I still have doubts, what do you think, (or know) about this?

[john8662]

What brand heads are they?

ALL I know of are Alabama Cylinder Heads = Chinese (you know what)

But, the other day I stopped in at the machine shop and they and some other brand of new in box 6.5 heads, I'll dig a little deeper and see if I get into more trouble.

The "Aftermarket" heads do claim the thicker casting, and more material in between the valves (which equates to less coolant flow IMO)...

J

[Kennedy]

All sounds typical. I wouldn't be afraid of the 506 block. That is what I used. The van vs truck is only difference in drilling. Coincidence OR engine mounting differences OR power levels that they crack less.

RJ can fix you up with an awesome setup.

[Patrick m.]

im still waiting to read about his final turbo (maybe i missed it ive had my hands full lately)
I have tried several, and have a good feel of what does what. I just cant see it on paper as the better educated can.

I have decided, torque or power down low wont be had with a 6.5L
2500 and up....you can make power.

[dieseldummy]

I have decided, torque or power down low wont be had with a 6.5L
2500 and up....you can make power.

I disagree, they can have power down low. Ya just need to know how to coax it out of them... I hope your new engine treats you well, sounds like you're getting a good deal.:cool:

[Patrick m.]

What brand heads are they?

ALL I know of are Alabama Cylinder Heads = Chinese (you know what)

But, the other day I stopped in at the machine shop and they and some other brand of new in box 6.5 heads, I'll dig a little deeper and see if I get into more trouble.

The "Aftermarket" heads do claim the thicker casting, and more material in between the valves (which equates to less coolant flow IMO)...

J

They are "Engine Quest" , turns out they cast all sorts of heads im trying now to find out where in the USA exactly they are.