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Broken Block - Usable as is, reparable or for metal recycling ?

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  • Broken Block - Usable as is, reparable or for metal recycling ?

    i bought from a french gentleman a supposed very good condition 875 sport engine with low milage. And that is true, under certain angles, it was looking good.
    After closer inspection i found that flywheel that was appart, was a useless for me as it was a 930 one, and that block got lighter after meeting the pavement or a rock.

    From experience, as this must have happened in the past:
    - For road use, can it be still go like this with 2 bolts missing ?
    - Can it be repaired soldering a new piece of aluminium ? If yes was kind of aluminium is it ?
    - Should i consider it for parts and get another block ?

    Thank you !
    Attached Files

  • #2

    You only have one bolt missing, the other small hole is a locating pin / dowel to locate the faces together (centre the crank to input shaft on transaxle)

    Thats a lot of ally though to fill, you would need after this to mill the faces flat.

    I am not sure the alloy but I would suggest perhaps finding a scrap block and

    Cutting this section out of scrap block but slightly oversize
    Trim your old block to mate the two together
    Bolt to transaxle bell housing to use as a jig
    Fillet the edges
    Weld in the fillet

    Problem is you will need to tear down the engine and bolted down as ideally you want the block hot to do this

    I find the cast to be reasonably soft so if you decided to just build up the area na dthen flat it off, its do-able but thats a lot of time and rods

    Bob knows a lot more about castings, blocks, fixing etc. than me


    / John


    • #3
      The imp engines and gearboxes are die cast aluminium and it is very difficult to weld without changing the properties of the material. If you just weld to it the metal becomes brittle and will crack.
      Need to learn about cast aluminum repair? If you want to know how to repair a crack in your motorcycle’s aluminum transmission casing, this is a must-read.

      Cast aluminum can be problematic, and fixing cracks only add more of a challenge to the welding process. Detroit welder Josh Welton of Brown Dog Welding tackles a cracked cast aluminum bell housing on a vintage Alfa Romeo. 

      For all the hassle involved and the amount of blocks that are available. I would replace the block


      • #4
        • Prepare the weld area. Remove the defect and remove the oxide layer with a brush or solvent.
        • Preheat before welding. Preheat generally improves welding results. The usual range is 212–572F (100–300C). Generally, aluminum alloys containing copper are welded at the higher end of that temperature. Castings will usually be welded in the as-cast condition but sometimes defects will not be uncovered until after heat treatment, so they are welded in the T6 or T7 condition. In 200 series alloys or for castings that require extensive repairs, it is recommended that T6 or T7 tempered castings be annealed before welding to avoid cracking.
        • Use weld rod that matches the chemistry of the casting or an approved substitute. Chemistry control in welding is as important as it is in melting for casting. Use of a general-purpose rod across all alloy systems will result in reduction of mechanical properties and color mismatches even though welding may be “easier.”
        • After welding, the weld needs to be dressed back to part contour. A common complaint of customers about welded castings is the weld has not been cleaned or there is a color difference. If a weld repair is noticeable with casual viewing, the repair has not been done correctly.
        • Heat treat after welding. Even though a good weld will have little porosity and a fine structure, mechanical properties will not be met if the repaired casting is not heat treated to the specification. Heat treatment will also eliminate the residual stress that may have been caused by the welding process.


        • #5
          i weld steel and brass, but aluminium i'm a beginner. Thank you very much for these very precise informations. I will measure the bore to see if it is an expensive 998 or larger, and if i can find an experienced welder. So if it is a 875 will just change it, as even in France, that is true a block is easy to get.