welding a steel crank

Discussion in 'High Performance Modifications' started by pinknuggit, Jan 8, 2007.

  1. pinknuggit

    pinknuggit Veteran Member

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    I'd like opinions from people who have either done this or ran an engine with this done... no "I heard" or "I think".

    What can I expect from welding up a damaged journal on a steel crankshaft as far as durability? I have heard a bunch of people with no experience say that they wouldn't run a welded crank in anything, but I'd like to find out from people who have actually ran a properly welded steel crank in a mild-power engine setup.
     
  2. rustbucket79

    rustbucket79 Veteran Member

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    First thing that comes to mind is whether that steel crank has been magnafluxed or not. If the journal cooked bad enough to need welding I would give even odds that it is also cracked.
    The next thing is unless you're building big power, a factory stock cast iron crank will take a crapload of power and abuse.
    I have personally welded up a CAT steel 350 crank that the guy had failed a rod, but it was only 3 low spots in the crank, not an entire journal. It is now serving duty on a 6/71 blown 350 in a mid 60's Impala. We leave the complete journal repairs to the experts, and only on cranks that are no longer available.
     
  3. pinknuggit

    pinknuggit Veteran Member

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    The spun journal isn't cracked or heated up, it has just been turned .030" already and it spun enough that it won't clean up at .010". I have already checked the crank (magnaflux and straighten), and it's straight as an arrow with no discoloration from getting hot or any cracks at all.
    The motor it's going in will be a 500hp Max street motor. I'm just worried if the welded journal will become a weakpoint and the crank won't be as strong as it was before.
     
  4. rebski

    rebski Veteran Member

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    Back in the day. (early 70's ) I would take steel cranks and weld them up for offset grinding them into strokers. If done correctly it's not a problem. The key is the knowledge of the person welding ! Then after its ground have it nitrated for surface hardness.

    With the price of good quality cranks is this really cost effective.
     
    Last edited: Jan 8, 2007
  5. rscamaro73

    rscamaro73 Administrator Staff Member

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    Is there any reason to keep this one versus getting a replacment ??

    I say this because for your power level indicated, you can prolly get a new crank for close to what it'd cost to get one welded up. At least check out that option....:bowtie:
     
  6. camertom

    camertom Veteran Member

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    In my day and after 14 years as an engine machinist I specialized in crankshaft repairs. In automtives we had no real issues even welding small cast iron ones. Industrial customers with forged steel John Deeres, Cats, Case' and larger scale Waukeshau's and White's had $1000.00's of working dollars on the line and wouldn't have allowed it if it was a problem.

    The mild steel ones are wonderful to weld. They should be pre heated and then insulation wrapped and cooled slowley. They will not be straight after welding however if they threw a rod they weren't straight to begin with. They should be "peened" straight NOT pressed straight.

    The sole caveat is if you happen to have a nitrided one. They can't be welded as they form thousands of tiny little bubbles in the surface.

    As along as the finish grind does a pro job on the radius' a steel crank weld repair is fine under tremdous load duty.

    I might add that "back in the day" the first stroker cranks for extreme HP were actually stock forgings built up on all 4 throws and then reground! They seemed to work fine when prepared proerly!
     
    Last edited: Jan 8, 2007
  7. gregh

    gregh Moderator Staff Member Lifetime Gold Member

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    I welded my Scat 9000 series crank this spring, just on the thrust surface mind you & had no problem using a technique similar to what Tom just described.
    It bent slightly but was straightened & ground & is currently in my engine.
    I don't know what you consider "mild power" but I'm running in the 400-450hp(flywheel) & hitting it with another 150hp from a bottle.
     
  8. pinknuggit

    pinknuggit Veteran Member

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    Thanks everyone, that's the kind of advice I was hoping to hear!

    yeah, I had my fair share of confusion when I tried to weld a big block crank that had been nitrided for a customer and got the big bubbly looking weld that didn't penetrate.. I had to grind the journal down past the nitride hardening, then build the weld up layer by layer.. talk about pita!

    Camertom, do you have any tips for a good weld? I'm using a peterson flux powder shield crank welder. What I usually do is heat the journal about to be welded with a propane torch, and I weld it pass by pass. Some people do a continuous weld with the machine transversing.. but I just lay a bead, scoot the tip over a cunthair, lay another bead, etc. I do that because it doesn't heat the journal up as quick and I can take a break if the journal gets too hot so that it doesn't bend the crank any. I've had pretty good results by doing it this way.
    The crank in question is getting welded up on the mains, and the rods are being left alone.
     
  9. 74RAT

    74RAT Veteran Member

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    ditto with camertom and rust. the bullnosed chisel peened in the radius,, and a big heavy hammer to straighten it. i've seen more problems with 231 buick v-6, 2.8 chevy, and 302 ford cast cranks breaking between the first rod and main or first rod and second main. these were in stock applications too,, without any major power produced. everything else didn't really have any problems. never any problems with steel ones. even the j/d, case, perkins, cat, cummins, waukasheau, minniappolis moline, etc... as mentioned,, did well. i also have good luck with your make a weld wrap or 2 and wait method. ditto with always grinding the journal first to get the penetration point below where the new journal surface will be,, and into the radius as well,, so that the radius and thrust cheek isn't part of the weld penetration point. it'll show cracks there if so. also,, verify that the wire/flux used for welding is for the crank material in use. there are a few different types of wire/flux material. sounds like you're on track though.
     
    Last edited: Jan 8, 2007
  10. rustbucket79

    rustbucket79 Veteran Member

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    Why not just grind the journals to .050" undersize, then you still have .060" if it needs another grind. ACL makes trimetal .050" u/s bearings.
     

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