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need it welded up on 2 mains , straighted and renitrated how would you recommend its a 4340 crank or how has one for sale its 4 inch stroke 2.75 mains 2.100 rods
crankshaft repaired
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Is it so bad that you can not use over size main bearings?
If you try and weld it you will have issues with the base metal heat treat. 4340 is a thru harding grade and at welding temperatures you will temper spots back and over harden other spots. You can talk to a shop that does submerged arc crank welding but if the mains are messed up that bad I would scrap it and start fresh.
If you try and weld it you will have issues with the base metal heat treat. 4340 is a thru harding grade and at welding temperatures you will temper spots back and over harden other spots. You can talk to a shop that does submerged arc crank welding but if the mains are messed up that bad I would scrap it and start fresh.
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5,695 Posts
Who made it? Ask them about repair work.
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6,312 Posts
My crank guy told me he couldn't weld the cheap China cranks and that if I hurt one he could grind it but not weld it. I spent the money for a Callies in my 565 because of what he told me. So you may want to check with whoever you plan to have fix it and see if it can be fixed. RM.
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My Crank guy says that even about some good cranks out there... unweldable. He seems to favor the Callies stuff over almost everything else out there.
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It APPEARS that nothing more than a grinding and some bearings would have you up and going. The journal doesn't look "ground away", just messy. Perhaps .020. It's not even showing signs of heat.
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49,830 Posts
I would feel comfortable taking the journal down to 2.000 as long as it was not a big power adder motor. I would just turn it 20-30 and get it renitrided.
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49,830 Posts
I would have the crank checked for twist and straight. If it is straight and tisted get it Index ground. If it is bent chuck it in the gabage.
I like the chinese crank only for this reason. If you tear one up who cares !
I like the chinese crank only for this reason. If you tear one up who cares !
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8,341 Posts
I think you got a little confused with the posts and who posted what.
"43665fastback" started the thread asking about his mains @ 2.750 with 2.100 rods.
"Bear" simply asked if "this" was fixable (with pic) but with no crank specs.
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49,830 Posts
Shit I would run 2.0 mains on a big checy to. I do not care. Rod bearing get there strength from oil film not diameter.
I would assume yes on both counts.
I would assume yes on both counts.
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628 Posts
I used to repair cranks at a machine shop & we did any material even cast. The trick is the journal cannot be welded over the nitride treating so it must be roughed down. Usually we would go .080 & then hit the sides with the side of the wheel to open them up past it. Then weld it, straighten, grind & send out to get nitride treated.
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That crank needs to be mag'd first before any decision is made.... there may be heat checks and even worse.... heat does nasty things.
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5,404 Posts
I am with the other guys, find a good crank shop, have it completely check out and go from there. That doesn't look that bad and you might be able to get it ground down for oversized bearings and have it re-nitrided. What does the ID on the big end of the rod look like?
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49,830 Posts
I would doubt a 4340 crankshaft would crack from a little heat. Most likely it has shrunk up a tad though.
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WOW that would make ET say OooUuuCccHhh!
Broking rods or pieces in your oil pan never looks good. What I was looking for was what the bearing looked like and if the actual rod end had contacted the crank journal. From that pic the bearing is still in the big rod end which is a plus. Get the crank check for cracks, index and see if they can ground that journal down and use over size bearing. Also check the oil hole from the main and see what if anything is in it. That babbit bearing should have given out long before a 4340 nitrided crank did, if not something is very wrong.
No to be funny but what did that sound like when it came apart?
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Bear whats odd about the damage is that it looks like it didn;t have an oiling supply issue. How was the bearing clearance ? Can you give us pictures of the slugs from the top and both sides ?
him Mike Lauer sent ya1 - 20 of 29 Posts
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