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Hot Rods Another metal casting adventure...in honour of Mr Mcgurk

Discussion in 'The Hokey Ass Message Board' started by Jethro, Nov 26, 2018.

  1. Jethro
    Joined: Mar 5, 2001
    Posts: 1,344

    Jethro
    ALLIANCE MEMBER

    So my last adventure was to make adapters to transition from Chevy 250/292 intake port to GMC 270/302 port. It turned out good but I was adapting a Weber DCOE triple carb intake and the Weber carbs are about $500.00 US each so I am looking for a more reasonable , cost effective(cheap) route to follow. I looked at old pics of GMC manifolds and McGurk was a popular manifold of the day. The McGurk manifold has runners that are separate from the "log" so I thought I could attempt that. I found that plastic plumbing elbows are roughly the shape and size I wanted so I started with that. I made some flanges with MDF and made a core mold from plumbing pipe. The castings turned out OK but I'm getting what look like pinholes and pimples on the exterior of the castings. I was thinking I was having a gassing problem but when I sand down the castings the pock marks go away. So I think I'm having a sand issue , not a gas bubble issue. Maybe a more experienced metal caster will chime in. Anyway, I got three useable castings for the runners and now I have to make a pattern for a "log" and top. mcgurk - 1.jpg mcgurk - 1 (1).jpg mcgurk - 1 (2).jpg mcgurk - 1 (3).jpg mcgurk - 1 (4).jpg mcgurk - 1 (5).jpg mcgurk - 1 (6).jpg mcgurk - 1 (7).jpg mcgurk - 1 (7).jpg mcgurk - 1 (8).jpg
     
  2. F&J
    Joined: Apr 5, 2007
    Posts: 12,887

    F&J
    ALLIANCE MEMBER

    I assume it's the sand also. Maybe moisture? (IDK)

    You likely already look at YouTube casting vids..."green sand" is something you can buy or make yourself.

    .
     
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  3. pitman
    Joined: May 14, 2006
    Posts: 4,482

    pitman
    Member
    from Hampsha

    Lookin' good there!
    She'll be well fed.
     
  4. treb11
    Joined: Jan 21, 2006
    Posts: 3,060

    treb11
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    Suggestions to reduce gassing: Allow molds to dry for one hour before pouring. Poke small vent holes through the mold with TIG wire or equal to aid venting. Avoid holding the aluminum at melt temperature too long.
     
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  5. Jethro
    Joined: Mar 5, 2001
    Posts: 1,344

    Jethro
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    I'm using petrobond sand so it shouldn't have moisture in it but I will try letting it dry out next pour.
     
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  6. catdad49
    Joined: Sep 25, 2005
    Posts: 2,547

    catdad49
    ALLIANCE MEMBER

    Are you sealing the mold with a wash? We used an alcohol based wash and after painting, you would light it to burn off the residual alky! The ones that made the cut sure look Great. Keep posting, this is good stuff.
     
    dwollam likes this.
  7. Pin holes or no pin holes, that is some neat stuff right there. Well done!
     
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  8. Jethro
    Joined: Mar 5, 2001
    Posts: 1,344

    Jethro
    ALLIANCE MEMBER

    The next step is to make patterns for the top and log part of the manifold. I used whatever leftover lumber bits I had lying around. Some pine , MDF and two old yardsticks, I think they are maple. I coated the moulds with fibreglass resin and sanded them to 400 grit. I tried casting the top and had some issues but my proof of concept says that this will work. I need to get some more petrobond as I kinda ran a little lean in some areas and had a couple minor collapses but as an exercise it worked out ok. mcgurk top - 1 (1).jpg mcgurk top - 1 (2).jpg mcgurk top - 1.jpg
     
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  9. Neat!
     
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  10. Jethro
    Joined: Mar 5, 2001
    Posts: 1,344

    Jethro
    ALLIANCE MEMBER

    I finished the "log" and top and then Bippity Boppity Boo.... Bell GMC - 1 (5).jpg Bell GMC - 1 (4).jpg Bell GMC - 1 (3).jpg Bell GMC - 1 (2).jpg Bell GMC - 1.jpg Bell GMC - 1 (1).jpg

    Whenever I post any progress on anything on the weekend or near a holiday it gets buried pretty fast ,I hope it will get some views. I'm pretty happy with this one!....Geez that sounded pretty needy huh?
     
  11. captainjunk#2
    Joined: Mar 13, 2008
    Posts: 4,271

    captainjunk#2
    Member

    thats some nice work and an eye candy engine
     
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  12. Tim
    Joined: Mar 2, 2001
    Posts: 8,701

    Tim
    Member
    from Raytown Mo

    Great work!
     
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  13. J. A. Miller
    Joined: Dec 30, 2010
    Posts: 1,050

    J. A. Miller
    ALLIANCE MEMBER
    from Central NY

    Nice work!
     
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  14. catdad49
    Joined: Sep 25, 2005
    Posts: 2,547

    catdad49
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    Great Work, Jethro! Merry Christmas to You and your Family.
     
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  15. slim38
    Joined: Dec 27, 2015
    Posts: 234

    slim38
    Member
    from Sudan TX
    1. H.A.M.B. Chapel

    Great work. Wish I had that talent. I might. Lol
     
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  16. Jethro
    Joined: Mar 5, 2001
    Posts: 1,344

    Jethro
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    Thanks catdad! Same wishes to you and yours!
     
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  17. jebbesen
    Joined: Aug 18, 2015
    Posts: 252

    jebbesen
    Member
    from Winona, MN

    Very Nice!
     
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  18. I don’t like it! But, I Love it!


    Sent from my iPhone using The H.A.M.B. mobile app
     
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  19. Patrick Crumley
    Joined: Sep 12, 2018
    Posts: 21

    Patrick Crumley

    That is absolutely awesome. Would love to have the ability to do this for my 250.

    Sent from my moto z3 using The H.A.M.B. mobile app
     
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  20. Duke
    Joined: Mar 21, 2001
    Posts: 557

    Duke
    Member

    That is excellent! Is this for the A?
     
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  21. Jethro
    Joined: Mar 5, 2001
    Posts: 1,344

    Jethro
    ALLIANCE MEMBER

    Hey Duke....it's been a while! How've you been?
    Yeah, going in the model A. since we can go fenderless now and I found a real vintage mill I can be like you and BCT and make a traditional car
     
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  22. Duke
    Joined: Mar 21, 2001
    Posts: 557

    Duke
    Member

    Things are going well. Still working on the A. Other projects keep getting in the way. Spent the afternoon fixing a 34 ford frame, instead of the A.
     
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  23. patsurf
    Joined: Jan 18, 2018
    Posts: 144

    patsurf

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  24. '51 Norm
    Joined: Dec 6, 2010
    Posts: 620

    '51 Norm
    Member
    from colorado

    I love making stuff out of plastic plumbing pipe. It's easy to work with and cheap enough that I don't worry too much if I scrap a part.
    Great job with the casting!
     
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  25. 50John
    Joined: Jun 24, 2005
    Posts: 130

    50John
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    Very impressive. Came out great. Do have a lot of experience casting before you started with your adapters?
     
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  26. 4woody
    Joined: Sep 4, 2002
    Posts: 2,063

    4woody
    Member

    Love it when Jethro posts a how-to piece!
     
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  27. Dick Stevens
    Joined: Aug 7, 2012
    Posts: 2,281

    Dick Stevens
    Member

    Very impressive, I love the design and the resulting intake system!!! :cool:
     
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  28. Jethro
    Joined: Mar 5, 2001
    Posts: 1,344

    Jethro
    ALLIANCE MEMBER

    Actually , I only started doing sand casting this year. Up until then I had done a little(very little) lost foam casting. I have spent quite a bit of time reading backyard metal casting articles and watching Youtube videos. I'm a trial and error (lots of error) kind of guy. The nice thing about having failures in aluminum is they can go right back into the pot. You lose a little each pour but you can recycle your mistakes . If you have basic woodworking skills and can visualize a negative space you can make basic patterns for casting.
     
  29. bct
    Joined: Apr 4, 2005
    Posts: 2,897

    bct
    Member

    I find your creativity astounding.... every single time.
     
    loudbang and 56premiere like this.
  30. ^^^^^^me too!
     
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