Slant 6 Block Crack

Slant 6 Engines

Future of this block:

  1. Trash heap!

    50.0%
  2. A machine shop can weld it and machine it good again.

    30.0%
  3. Hold my beer, I'm just gonna use it!

    20.0%
  1. J Glenn

    J Glenn FABO Gold Member FABO Gold Member

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    What do you think of this? Fixable? Ignore? Future Coffee Table? I *was* planning a full rebuild with upgrades, head porting, higher compression for this engine. The head looks good. Actually, the cylinders look really good. But this crack?! Ugh. Is this common? Why would the block crack at the alternator bracket stud?

    1974Aspen225_cracked_block.jpg
     
  2. RustyRatRod

    RustyRatRod Lemmie see your b00bs. FABO Gold Member

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    That's a stress point where the stud screws in. Could be it was removed for some reason and when it was screwed back in there was some trash in the hole and it cause the crack. Could be some dumbass cross threaded the stud. Who knows why it cracked? Cast iron is some great stuff, but that's one of its downfalls. It can crack just sittin there. As many slant blocks are out there, I don't think I'd take a chance. All it could do is leak oil....but like cast iron, unless you find the ends and stop the crack, it will keep cracking. Then the question comes into play, Is it worth fixing, or do you find another block? I say fins another block.
     
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    • valiantpatrol

      valiantpatrol FABO Gold Member FABO Gold Member

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      That's a tough call. not in a water jacket so if it sealed up and did not leak oil it would probably be OK. Tough part is knowing it's there and the lingering doubts. Flywheels sometimes get what looks like cracks in them but after re-surfacing they all disappear and this might be like that if your lucky. Cause would be pure speculation and could be any one of a dozen things. It get it mag checked to see how deep it is and does it stop, as it appears to, and not extend all the way into the adjacent cavity. If it did extend in that adjacent cavity I consider a different block.
       
    • J Glenn

      J Glenn FABO Gold Member FABO Gold Member

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      FYI: the crack stops at the bolt-hole.
       
    • RustyRatRod

      RustyRatRod Lemmie see your b00bs. FABO Gold Member

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      Are you sure? Have you removed the stud and looked into the hole to see if the crack goes into the threads? I just bet it does.
       
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      • SGBARRACUDA

        SGBARRACUDA ROY FABO Gold Member

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        Where does it stop on the other end?
         
      • J Glenn

        J Glenn FABO Gold Member FABO Gold Member

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        You're right... the crack does NOT stop at the hole... I'm gonna chuck this engine.

        1973Aspen_crack.jpg
         
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        • A56

          A56 MoParAffliction FABO Gold Member

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          I'd be real concerned with it finally breaking completely off
           
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          • RustyRatRod

            RustyRatRod Lemmie see your b00bs. FABO Gold Member

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            You COULD go ahead and break that corner off. It could be brazed back on.......but what'd it cost would probably outweigh another block.
             
          • RustyRatRod

            RustyRatRod Lemmie see your b00bs. FABO Gold Member

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            A possible cause for that was the fasteners working loose that held the bottom alternator bracket on.
             
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            • Darter6

              Darter6 Well-Known Member

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              Too bad you aren't closer. I'd give you a short block.
               
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              • pishta

                pishta I know I'm right....

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                If it were Farmer Johns combine, he'd JB weld it. That's not even a stress point for the alternator bracket as it wants to pull the bracket closer not farther under belt load. I bet the rear and top alternator bolt fell out or loosened up enough for the mount to cock toward the radiator, taking the corner of the block with it. If blocks are abundant, get another. If they are not, that is runnable. If its not an A/C car, run the alternator on the driver ala A-100 or 1960 generator style and forget that mount point, Goop up a stud and run it in hand tight and forget about it. @RustyRatRod I agree on your assumption after I wrote this I saw yours. Only way there could be stress on that bolt in that direction.
                slant-six.jpg
                 
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                • Darter6

                  Darter6 Well-Known Member

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                  pishta, I'm glad you said it first JB Weld it !
                  Clean, clean, clean and drill the crack ends at the block with a small drill bit to stop further travel.Stud hole add JB to the cracked threaded area and re-tap after it sets up. I fixed a Pontiac Iron Duke with a busted head boss that way same as yours into the water passage.
                  BUT if you are going full blown into a performance build,look for another block.
                   
                • J Glenn

                  J Glenn FABO Gold Member FABO Gold Member

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                  I'll find another slant block. I'm sure I wont regret having an extra, extra engine... Except the tripping over it problem! But I'm kinda bummed because that was plan for a Pandemic Winter project. I can still do the head, though... I want to try porting! Or this might be the winter that the Valiant gets power steering. Or, God forbid, an interior!
                   
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                  • Princess Valiant

                    Princess Valiant Duster specialist FABO Gold Member

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                    I'd JB weld that and use it.

                    It could have been from a collision being on n the very front corner like that. I've seen engines and engine parts out of wrecked cars like that.


                    Maybe your car wasn't wrecked but in the past 60 years it could have come out of a wrecked car at some point.
                     
                  • MOPAROFFICIAL

                    MOPAROFFICIAL FABO Gold Member FABO Gold Member

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                    Drill and tap and little bolt through the crack to keep it together.
                    Not sure its thick enough though.
                     
                  • Slantsix64

                    Slantsix64 Well-Known Member

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                    I have that same crack on mine just epoxied it like 4 years ago, if your worried i would run that A100 slant six alternator set up. but your engine good luck!
                     
                  • MOPAROFFICIAL

                    MOPAROFFICIAL FABO Gold Member FABO Gold Member

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                    Time to get creative. Put a grade 5 stud in it...then tap a smaller bolt the size of cotter pin through the side through the block and stud.lol
                    Garbage or diff bracket setup
                     
                  • J Glenn

                    J Glenn FABO Gold Member FABO Gold Member

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                    Do you know what casting/year block you have?
                     
                  • jos51700

                    jos51700 Hemi Orange you glad it isn't a political avatar?

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                    Weld it and run it. Either drill the ends and grind it out, tig it up with stainless, keensert it and move on.

                    Or bust it out, fill the entire lug with weld, and drill and tap it. If it just holds the alternator the load is minimal and it's probably cracked from an impact or stupidity. It doesn't see compression, oil pressure, or coolant system pressure. You could silicone it to hold the oil in if you didn't need the alternator.

                    If it's where I think it is. I'm not super familiar with slant 6's like some on this board.
                     
                  • MarPar

                    MarPar Hello... FABO Gold Member

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                    ROAD TRIP!!

                    24Te.gif

                    :D
                     
                  • Slantsix64

                    Slantsix64 Well-Known Member

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                    1979 Cast Crank
                     
                  • vitamindart

                    vitamindart Well-Known Member

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                    the current slant in my car has a crack in the water jacket. I took the advice of JB welding it up and its been good ( so far ) figured it would give me the chance to improve some other parts of the car while I ran it as is. at some point im cramming some boost in this one so... might as well learn on this runner.
                     
                  • halifaxhops

                    halifaxhops It's going to get stupid around here! FABO Gold Member

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                    Look into stich N lock was amazed with the results.
                     
                  • RustyRatRod

                    RustyRatRod Lemmie see your b00bs. FABO Gold Member

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                    IF I was gonna repair it in any way at all, I'd break that whole corner off first and go from there. It could be brazed back together with a high nickel welding rod.
                     
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