Crank

Discussion in 'Mopar Performance Issues' started by cuda620, Jan 9, 2018.

  1. cuda620

    cuda620 Well-Known Member

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    How durable is the 440 forged crank for a 451 build? Not rehardening. Just cutting/ grinding the counterweights and taking the .125 off the mains to fit. Does it leave the mains too soft? I’m sure it’ll run. I’m interested in durability. Thanks all.
     
  2. MOPAROFFICIAL

    MOPAROFFICIAL Well-Known Member

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    I've turned one about 6900 rpm, never had any problems. Probably made 485 hp, nothing radical, mild port job 906 heads.
     
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    • JBurch

      JBurch Well-Known Member

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      Something to think about.............they were cutting down 440 cranks to make 451's long before they started to make specific cranks for the build........I never heard of the cut down cranks being unreliable....actually you will pick up a slight improvement due to the ground fillet radius on the main journals (that are stress reducing) rather than the rolled groove (that are stress inducing) journal fillets.

      If you are super paranoid, you can have the block line bored to except the 440 crank as is.....IF you can find a shop that can and will bore the block that far......reference "Mopar Action" Eherenberg's "Project Bold Beeper" build.
       
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      • rumblefish360

        rumblefish360 so close yet so far away

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        It will be something I would not be worried about. Unless you plan on something extreme racing with it. Are you racing or just building a street hot rod? What is your perspective output and power?
         
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        • cuda620

          cuda620 Well-Known Member

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          I’d rather not have the block done. A couple of shops recommended re- hardening the crank... but it’s what they offer. I’m tryin to keep it a budget build. I’m used to building 383’s and 440’s but never did a 451 so looking for opinions. Only pistons I’ve found without oil support rings so far are ROSS. I’d hate to build it and be 1000 miles from home and loose a crank.90% street car with some playing. Not after the last hp. Thanks.
           
        • JBurch

          JBurch Well-Known Member

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          I'll be brutally honest, never heard of re-hardening the crank after cutting; what is the process they propose to use to re-harden the crank? I can see the possibility of the crank becoming brittle after such a process.

          When any of the factory crank were hardened at the factory, they were only surfaced hardened, only to a depth of .002 to .003 of an inch; other wise they were of a uniform hardness thru out.
           
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          • rumblefish360

            rumblefish360 so close yet so far away

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            I have heard of that process done before after cutting the crank. It’s no big deal to have it done or not. A lot is on intended useage. Non re hardened cranks are fine for street & mood strip. If you were going to be racing it hard, the process maybe worth your while.
            Mental HP? IDK
             
          • IQ52

            IQ52 Well-Known Member

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            If your crank grinder knows what he is doing, there is no way I would worry about it. I have a 451 with a ground 440 forged crank. Never had it hardened. Made 620 HP and drove around in a 71 Road Runner. Tore it down and inspected the bearings. Put it back together a little differently and made maybe 100 dyno runs from 700-780 HP. Tore it back down and de-tuned it to 580 HP and installed it in the shop truck. Still has 40 psi oil pressure at idle and 70 psi at rpm. I'm thinkin' you'll be okay.
             
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            • cuda620

              cuda620 Well-Known Member

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              Thanks! Are you using a stock or hv pump?
               
            • IQ52

              IQ52 Well-Known Member

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              I am a high volume pump man.
               
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              • Marcohotrod

                Marcohotrod Well-Known Member

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                forged crank - no problem. cast - maybe. metal is hardened/heat treated in an oven at certain temps and certain periods of time depending on the alloy and the results u are after : such as harder or more ductile; by someone that knows what they are doing
                 
              • oldkimmer

                oldkimmer Well-Known Member

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                My buddy had his crank chromed. Kim
                 
              • rumblefish360

                rumblefish360 so close yet so far away

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                Chrome crank? Part of a lamp? LOL
                 
              • famous bob

                famous bob mopar misfit

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                I ran a repaired crank in a hemi a couple of times, one was hard chromed after being repaired. The factory hemi cranks were a little less then .002 nitride, not heat treated.
                 
              • cuda620

                cuda620 Well-Known Member

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                I know an industrial chromer. Like that?
                 
              • Marcohotrod

                Marcohotrod Well-Known Member

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                nitriding is a fancy form of heat treating, where we remove air, and use only nitrogen. I run custom nitrided 11/32" valve guides-good since 1995. hard chroming is old school-good for old engines where only a cast crank is available
                 
              • famous bob

                famous bob mopar misfit

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                Chrysler said their nitriding was a chemical process to harden, and was very thin. Steel cranks that spun bearings, or had thrust surface troubles were chromed too. Had one in one of my hemi`s , bought it from Jim Hale.-------back in the day.