Crankshaft Question
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Mountain Pass
Joined: May 2013
Posts: 131
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From: Spanish Springs
Crankshaft Question
Just got this Crankshaft back from the machine shop. It's off a 390 big block. It was turned to 10 under. Before I had it turned, I had a bearing/wrist pin failure, which caused the connecting rod to cut into the side of the journal. The machine shop says its fine, but I'm sceptical. Does anyone else see any issues with this? Am I just being paranoid?
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Last edited by jonezzzman; Aug 5, 2013 at 12:01 PM. Reason: change image
Postmaster
Joined: Mar 2011
Posts: 2,698
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From: Taxachusetts
Has the offending rod been checked for true-ness?
To cancel your doubts - plastigauge both rods in a few spots. Or slide a mic across it if you've got a good touch. Looking for the dreaded 'hourglass' shape here...Then put one rod together with berrins and oil - ease it back and forth across the journal at a couple different rod / crank angles. Put both together and check for end play and rod to rod clearance. You can't tell with the bare eyeballs - you need to check it in an "operating" situation. If you're ecstatic, put 'er together!
Need I say to keep a steady, light touch?
To cancel your doubts - plastigauge both rods in a few spots. Or slide a mic across it if you've got a good touch. Looking for the dreaded 'hourglass' shape here...Then put one rod together with berrins and oil - ease it back and forth across the journal at a couple different rod / crank angles. Put both together and check for end play and rod to rod clearance. You can't tell with the bare eyeballs - you need to check it in an "operating" situation. If you're ecstatic, put 'er together!
Need I say to keep a steady, light touch?
Hotshot
Joined: May 2003
Posts: 11,141
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From: south louisiana
I'd send that crank to the scrapyard. You have nothing there to guide the rod and keep in in alignment, not to mention the rough edges that will allow stress cracks to form. Get a new machine shop to do business with while you're at it. That one CLEARLY is one to run away from. It never should have been turned to begin with. Now you're stuck paying for a turning job that's worthless.
Posting Guru
Joined: Oct 2006
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From: nunya
I'd send that crank to the scrapyard. You have nothing there to guide the rod and keep in in alignment, not to mention the rough edges that will allow stress cracks to form. Get a new machine shop to do business with while you're at it. That one CLEARLY is one to run away from. It never should have been turned to begin with. Now you're stuck paying for a turning job that's worthless.
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Mountain Pass
Joined: May 2013
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From: Spanish Springs
Thanks for the feedback.
I gave them the benefit of the doubt; took it back to the machine shop along with the pistons, rods and bearings to have them check it. They are going to repair it and may turn it to 20 20 if it needs it. They also checked my rods and told me one was slightly twisted. They are going to fix the crank and swap one of the rods at no charge.
Of course, I could still change my mind. However, the technician seemed pretty confident that they could fix it. And, I'm told they are a reputable shop from a friend of mine who owns an automotive repair business. He does business with them all the time and says they are very good.
I'm also having them balance the rod and crank, etc. for an extra charge.
I gave them the benefit of the doubt; took it back to the machine shop along with the pistons, rods and bearings to have them check it. They are going to repair it and may turn it to 20 20 if it needs it. They also checked my rods and told me one was slightly twisted. They are going to fix the crank and swap one of the rods at no charge.
Of course, I could still change my mind. However, the technician seemed pretty confident that they could fix it. And, I'm told they are a reputable shop from a friend of mine who owns an automotive repair business. He does business with them all the time and says they are very good.
I'm also having them balance the rod and crank, etc. for an extra charge.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
Thanks for the feedback.
I gave them the benefit of the doubt; took it back to the machine shop along with the pistons, rods and bearings to have them check it. They are going to repair it and may turn it to 20 20 if it needs it. They also checked my rods and told me one was slightly twisted. They are going to fix the crank and swap one of the rods at no charge.
Of course, I could still change my mind. However, the technician seemed pretty confident that they could fix it. And, I'm told they are a reputable shop from a friend of mine who owns an automotive repair business. He does business with them all the time and says they are very good.
I'm also having them balance the rod and crank, etc. for an extra charge.
I gave them the benefit of the doubt; took it back to the machine shop along with the pistons, rods and bearings to have them check it. They are going to repair it and may turn it to 20 20 if it needs it. They also checked my rods and told me one was slightly twisted. They are going to fix the crank and swap one of the rods at no charge.
Of course, I could still change my mind. However, the technician seemed pretty confident that they could fix it. And, I'm told they are a reputable shop from a friend of mine who owns an automotive repair business. He does business with them all the time and says they are very good.
I'm also having them balance the rod and crank, etc. for an extra charge.
Posting Guru
Joined: Oct 2006
Posts: 1,360
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From: nunya
You CANNOT repair that crank by simply turning it 20/20. To repair the shoulders of the journals, it would have to be welded, and done by someone who has FAR more experience than that machine shop has. Junk it and find another crank NOW !!! That "Technician" is full of **** and should be avoided at all costs. Ditto for a shop that would hire the POS.
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Mountain Pass
Joined: May 2013
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From: Spanish Springs
I really appreciate the honest feedback. I may reconsider balancing and let them fix it at no charge. Just to see what it looks like. They said they were going to build it up by welding it and then turn it again, but only if it needs it.
Looks like I can get a crank with bearings at rockauto.com for $200. These are from Crankshaft Supply, Inc. Do you guys know anything about this company?
I will also give Survival Motorsports a call. Thanks for the info.
Looks like I can get a crank with bearings at rockauto.com for $200. These are from Crankshaft Supply, Inc. Do you guys know anything about this company?
I will also give Survival Motorsports a call. Thanks for the info.
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Mountain Pass
Joined: May 2013
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From: Spanish Springs
Just talked to Barry at Survival Motorsports. They have a 20/20 crankshaft for $200. No core. $40 shipping. I think I've already made up my mind. Thanks again for the feedback.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
Well that's a relief after that "benefit of the doubt" post. You couldn't have picked a better company to get a replacement from. 
Even if that machineshop HAD been able to fix that crank, it would have cost you more than a stroker kit would have cost, even then I wouldn't trust the finished product. It would have to be welded, machined, then straightened, then mag'd for cracks before it could be considered for reuse. You're not going to get all that done for $240.
Thread Starter
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Mountain Pass
Joined: May 2013
Posts: 131
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From: Spanish Springs
The bummer is that I was planning to have this engine rebuilt so I could drive my truck for Hot August Nights here in Reno. Looks like its not gonna happen. But, I'd rather do it right the first time.
Hotshot
Joined: Jul 2005
Posts: 13,834
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From: Middle Tn.
It's also a lot cheaper the 1st time.
Thread Starter
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Mountain Pass
Joined: May 2013
Posts: 131
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From: Spanish Springs
OK...so I received my crankshaft today, which could have been packed a little better. I'm completely frustrated and am not sure what to do. The box has lots of holes in it from the crankshaft resting on its side and rolling around in the box. I don't even know if its still straight. I don't know what to do. It looks fine but there's pretty good chance that its bent out of shape. Should I have this thing check for straightness? Any recommendations? Is there any way to tell if this thing is straight by laying it in the block? Do I need to have this professionally checked?
Last edited by jonezzzman; Aug 14, 2013 at 06:12 PM. Reason: Rephrase