Carnage........Whats your take?

Sometimes with a bad balance job you notice strange things like stuff coming loose under the hood that seems out of the normal, the rearview mirror vibrating at high rpm etc.... the stock external balance cranks have issues when operated above 5500 a bunch. I had two that cracked on me years ago but they were caught before they blew up.
 
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Well, I've question the balance on this motor since we first got it from the machine shop.
 
Number 6 in the above pic. After cleaning the gunk and oil off the main caps and such....there WAS some BAD detonation going on...was hard to see last night...
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turbonut85 said:
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Wow thats defiantely a blow out. I dont think that looks like something getting beaten on it, looks a lot like a pressure situation. If it was gettting beat on, it would have jagged indentions, this still looks pretty smooth.

Now keep in mind, Austin was having some severe crankcase pressure issues that started a while after the Power Tour. Possibly cracked the cylinder wall below the water jacket and the crack eventually grew?
 
Oh wow! Thats some BAD detonation!!!!!!!!!!!!! I'll bet the motor was detonated so badly that it caused the cylinder wall, which is already thin on a 4.1, to blow. Then eventally taking everything out. Thats some severe stuff to make the cap look like that.
 

That cylinder does not look like damage from over pressurization, my guess is that the damage happened after the crank snapped and was cantilevered. It would bind the piston in the cylinder breaking the wall out. To me it's consistent with the way the rods are bent and the piston pin pulling out of the piston. Notice the two cracks running along the axis of the cylinder as well as a circumferential crack. Not consistent with over pressurization from what I can tell.

Thanks for the info on the pressure fatblackracing, that makes since to see higher pressures when the thermostat is closed. Do you have similar measurements for when it's open?
 
Oh yeah, here are the pictures from that ford crank that I have, notice the nice patina from setting for 10 years. This one was just good ol' fashioned metal fatigue at around 100k miles. No detonation or high rpms, abuse or failed balancer, I think I just got a crank from the bottom of the proverbial bell curve:) . I just put another crank and bearings and it was good to go. Sorry for the crappy pictures, I had this same camera when the thing broke 10 years ago.
 

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Yeah....free timing gear with purchase of the front 2/3.....not sure why, but I can't seem to get it off the crank...
 
turbonut85 said:
Crank was "dry magged".
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A dry mag on a crank is not good enough. You'll miss small cracks this way. The crank should have been wet magged. I agree with Dr. Boost that the machinists explanation is odd to say the least. I've seen engines hydrolocked and they bend rods like he said. The crank was probably cracked before you installed it in the engine.

Neal
 
I don't know if this pertains to the buick world, but I know with other brands, going to billet caps, not only do they all have to be line bored, the bolt holes also have to be squared up with the block. I've heard of caps not being drilled out correctly and really messing stuff up
 
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