The Great 2 piece crank mystery

[auslander]

LOL, so my buddy's crank busted, luckily as soon he heard a knock he turned the motor off, so he didnt get the rod through the case.

My question what do you think caused this???

Motor was meticulously maintained, spent its life in a split window camper, motor was not abused or raced. A little history:  2276 82mm crank, 94mm jugs, Engle 120, rods are short 5.4s, full flowed, sand sealed, Denham stock valved heads, may or may not have used the 1.25 rockers, 40mm Webers, Mallory dual points dizzy.
[http://images.thesamba.com/vw/gallery/pix/769036.jpg[/img]


The case "seems" to be okay. :: 

[dcuplover]

welcome to Chinese made parts.......

[martin]

Here's a pic of my dad's 67 original stock engine bus crank with the original German crank cracked (back in the 70s). It happens even to stock VWs. Funny he had no problem getting home on his highway trip with it like this, lol.

[neil68]

It's interesting how many broken cranks are either stock German or welded German counterweighted strokers.  Haven't seen many breakage problems noted with the Chinese forged strokers.  Could it be that the 40-year-old German forgings just can't hold up anymore in some applications?

[martin]

The above one was only a few years old at the time in our family VW bus.

[Dougy Dee]

welcome to Chinese made parts.......

Take another look. That's a welded counterweighted crank.
crap happens!

[Jason Foster]

my welded demello crank broke at center main a number of months back.  oh well poop happens.

  mine destroyed a rod and the case and cracked a valve guide boss on #4 cylinder of head oh yeah and the cam is 3 pc. now.  and smacked 2 pistons into crank.  Happened in water box during burnout.

[gkeeton@zbzoom.net]

Two of the three welded stroker cranks I've seen in engines, to be rebuilt at the shop I work at, had the weld build up for the stroke starting to crack. Maybe this could have caused a crack that lead to the breakage. Another broken crank incident I looked at, with a stock 69 stroke crank, had the flywheel come loose. Was the flywheel loose?

[David Ward]

Sometimes welding the journals to machine them out to 82mm or beyond simply takes the crank beyond its limits.  I had an EDS 82mm welded crank that became a "doorstop" after I had it magnifluxed.  The crank wasn't that old, but I needed to have the journals polished and decided I should have it checked.  Cracked - badly, pretty much like the pictures above (near the journal cheeks).

$hit happens.

[J Dotson]

I can see its a welded stroker.My guess it did not get the right heat treat after welding and or they missed the crack check on it.One them thangs.

[Csaba]

Based on what I can see, there was a crack at the edge of the main journal that failed.  I have tested quite a few welded VW cranks in my day...some of them freshly processed, and they were cracked after welding.  Most of them in the rod journals, but some on the main journals.
If you look at the fracture face, the smooth area will show 'beach marks', like ripples in the sand.  These marks will get larger from the fracture initiation point, until the point where the crank ultimately let go.  That is where the fracture face looks rough and grainy.  It is actually amazing that so much of the crank held together based on the load this engine saw.
With regards to how this happened is anyone's guess, but I would start by looking at the corresponding bearing and the diameter of the saddle.

[camch]

I would like to are the rear main bearing closer