Lbz Broken crank

[Ironworker15]

A friend of mine got this complete Lbz with a broken crank for a steal. Upon teardown, we found the crank broken at the 7/8 rod throw. Never saw one break here. Usually , they're broken towards the front of the block. Going to tear it down the rest of the way and check the main journals. What are the chances it's useable? Hes looking to use it in a build and then sell his running engine. Here's a few pictures of the break. Cylinder walls definitely need an over bore. I assume the pistons were slapping around in there before the engine shut off. What are you guys thoughts? Worth sending to a machine shop for inspection? Or just sell any usable parts and call it a day.

 

[PureHybrid]

Use it

 

[Ironworker15]

That's what I'm leaning towards. He's going to send it out to the machine shop and have it looked at. Surprised to see the crank break there though. Must've sounded pretty wicked. Haha

 

[1FastBrick]

I wonder if an Injector let go or something?

If there is no obvious damage to the block I would send it out to the machine shop and build it.

 

[Bdsankey]

If the block measures proper I would use it. The key is getting it checked by a competent machine shop as it's usually a 50-50 shot of a block living after breaking a crank.

 

[Ironworker15]

That's the plan. I almost bought this block to use for my build, but decided to use my current running engine instead. Didn't feel like taking a gamble and being out the cost of the block plus inspection if it's not usable. But for the $300 he paid for it , should be able to recover at least that from selling the heads, covers, ect.

 

[ikeG]

Last 2 cores we've torn down had the main bore cracked where the broken crank spun the bearing. These pics are 2 different blocks. The cracks and markings are darn near identical.

It's also been a toss up on where the cranks are breaking, front or rear. Mostly lmls coming thru these days.

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[Ironworker15]

Wow, look identical to me. Like I said, that's why I wasn't keen on taking the gamble. Id rather run a block I know is good rather than use one that has a broken crank. Even if it checks out good, I'm sure the broken crank does damage to the block that can't be measured or seen by eye. Lots of weight spinning around in there. Just my opinion on it though. No hard facts to prove it.

 

[1FastBrick]

Last 2 cores we've torn down had the main bore cracked where the broken crank spun the bearing. These pics are 2 different blocks. The cracks and markings are darn near identical.

It's also been a toss up on where the cranks are breaking, front or rear. Mostly lmls coming thru these days.

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From What you have seen, Do they always spin a bearing when the Crank breaks?

 

[ikeG]

From What you have seen, Do they always spin a bearing when the Crank breaks?

Most of the time they do spin one. Hardly ever have to scrap the block though. I can only remember 3, maybe 4 that were bad from the spun bearing. And these 2 take the cake, cracking like that.

If you are buying a core engine, its far safer to purchase one that has a bad piston instead of a broken crank. I used to not be afraid of them either way but just went thru 2 bad ones in a row.

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