Removal of mottling on crankcase

Paul Venne has requested advice regarding potential approaches to the removal of mottling on the crankcases of an old OS Max-S 30 RC and an OS Max-H 40 RC. We all encounter otherwise nice engines with mottled cases, so this is of general interest. Any suggestions??

7 thoughts on “Removal of mottling on crankcase

  1. I tried walnut shells in my blaster cabinet and it worked, but it was a very slow process. I suspect the soda blasting would be quicker.

  2. I have no idea at all how to raise an item other than as a reply to an existing item. Even though you seem to have catered for this. I cannot find how to do it.
    I have some comments about your feature on the Delong diesel. Firstly, thank you for your flattering comments about my crankcases. I can assure you that they were the result of much sweat and tears, but luckily no blood. There is a very simple way to distinguish my replica cases from the originals. The front and rear of the mounting lugs are radiused on the originals, but for ease of making the cast iron die, my replica cases have square cornered mounting lugs. Very easy to spot. Although I did make about 20 fully machined cases, the die still exists though not in my keeping, so more replicas may appear one day.
    And a comment about the Motor Boys, whom you said in your artical did not sell castings nor plans for their projects. Whilst it is true that as a group we did not, the late Roger Schroeder did sell his castings commercially and drawings were included with his casting sets. Some of his castings originated from Motor Boys projects.
    And finally for you to edit out, I had no knowledge of your being invited to become a member of our group, so perhaps that was just between yourself and Ron. The group certainly did attract a few hangers-on who assumed they were somehow members because of their regular and oft unwanted communication with the group. I do not refer to yourself in this way and I will not name anyone. Membership was by invitation after discussion among the members, and we were each allocated aliases. For example ron was the Brisbane Motor Boy, so he was BMBI, I was the Empire Motor Boy, KCEMB etc.
    Ken Croft, now resident in SW France, and no longer mking engines.

  3. Thanks for this, Ken! I’ll amend the DeLong article accordingly.

    As far as my becoming a member of the Motor Boys by invitation, it wasn’t just between myself and Ron. In fact, I had nothing to do with it – I never lobbied for, or even suggested, such a move – it came at me right out of the blue. And it wasn’t a unilateral decision by Ron – to my certain knowledge, David Owen at the very least was party to the decision. Moreover, I was added to the list officially and openly – Ron wrote to me out of the blue to tell me that I’d been added, after which my name appeared in the “Motor Boys” listing on MEN, where it may still be seen. To be honest, I could never really understand why I was added – it was just something that some (clearly not all) of the others decided to do.

    Anyway, the Boys are now no more, so it’s all water under the bridge!

    Hope retirement in France continues to treat you well!

  4. Hello Adrian, Derek Butler sent me this discussion as I can as asking him where one could get hold of the motor boys plans cd. This may be a long shot, but worth a try.
    I’m a amateur diesel engine builder from Perth WA and would like to get hold of these plans.
    Thank you for your time.

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