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Technical Sand casters inside (single blade throttle body)

Discussion in 'The Hokey Ass Message Board' started by blue88coupe, Aug 24, 2017.

  1. blue88coupe
    Joined: Jul 16, 2011
    Posts: 11

    from TX

    I'm working on casting a single blade throttle body for use with old school style mechanical fuel injection, much like the toilet designs of today. I have a couple questions on the pattern piece.

    I see in this thread: That @alchemy has his pattern looking much more refined in terms of paint / finish. In the thread he says he "primes" then uses a "smooth coat of krylon." Are these rattle can deals? Sorry if im paint stupid, I've always just rattle canned my cars flat black or shot a rattle can of this on my parts and then scotch brite / light sand them:
    Any information on making my part look more refined would be greatly appreciated.

    I need to make a 3.5" x 6" core. I'm gonna go scavenge a piece of PVC or something with a. 3.5" ID that i could use as a core box. If that doesnt work out I do have a boring head on the mill that would get the job done, but it would probably suck going that in wood. Other option is a hole saw which would leave the hole finish pretty rough and take up a ton of time to smooth out. Any "outside the box" ideas?

    This is where im at with the pattern right now, its a split casting, i still need to make bosses for the throttle shaft and stop. I need to turn the two split halves of the "core" for the top and bottom to size and glue them on to the larger pattern. I'm thinking I might sandwich them between two smaller solid patterns and they'll hold together on the lathe long enough to get the OD to the right size on the split pattern.

    As always the answer to "why dont ya buy" or "billet" is "because I can!"
    chryslerfan55 likes this.
  2. ghornbostel
    Joined: Jan 3, 2012
    Posts: 131


    Core box is split same as pattern. Use a ball end mill and cut most of the material out of the core half first. Then with a small amount of trig you plot the path of the end mill radius to the radius you need for the core you want. Using a rotary table works for curves should you have any in the port or choke. The smaller the XZ dimensions determines the finish. Make the box half twice the length you need, cut it in half so you only have to go through the XZ moves once.

    Sent from my iPhone using H.A.M.B.[​IMG]
    Last edited: Aug 24, 2017
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  3. blue88coupe
    Joined: Jul 16, 2011
    Posts: 11

    from TX

    I see! I dont have a rotary table. The picture looks like it could be done on a basic manual mill. It might take some time but thats better than what I've come up with. I have quite a few ball end mills to work with

  4. ghornbostel
    Joined: Jan 3, 2012
    Posts: 131


    Yes. The finish is fluted and can be sanded out easily.
    The rotary table is used for a curved core.

    Sent from my iPhone using H.A.M.B.
    Last edited: Aug 24, 2017
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  5. blue88coupe
    Joined: Jul 16, 2011
    Posts: 11

    from TX

    Got the core box started, its glued and nailed on the edges so it can be cut in half and bored out. Got the core prints attached to the main mold body as well as some bosses on each side to give the throttle shaft a little extra support. Next couple days I'll fill in the holes where I drilled for the dowels and fillet everything. Making progress
    turboroadster, cadillacoffin and fauj like this.
  6. Three Widow's Garage
    Joined: Jan 18, 2010
    Posts: 203

    Three Widow's Garage

    As far as surface finish goes aluminum ill pick up pretty fine detail if poured right. Rattle cans are fine but you will need several coats with sanding between I usually go down to 220 / 240 grit then spray a good full coat on top of that.
    most of the Rustoleum products don't sand worth crap unless the dry for several days. Deft lacquer dries quick and sands good just don't get the water based type. Another thing to keep in mind try to keep the metal thickness uniform as practical throughout the part, thick areas will cool slower than thin causes weird shrinkage issues. Also hard to get aluminum to flow much thinner than 1/8. " JJ
    turboroadster likes this.
  7. Here are some shots of a couple sand castings I have done. First is a 4bbl, divided runner manifold for a 230 series Chevy 6. Had to also divide the Siamese ports in the head but the thing worked great.

    The second is a fake 4-hole Hilborn injector for my Willys. I used a real Hilborn scoop on it. Was a real fresh air scoop!

    Here are the cope and drag for the casting for the Hilborn scoop


    This is the pattern for the cores that hollow out the stacks. Made from ASB pipe.

    This is the pattern for the scoop. Two halves are identical.

    This is the cut-off from the final casting when I sized it for my hood.

    The final product.

    Not just a pretty face, it is a function fresh air scoop!

    Drawings for my Chevy 6 intake manifold

    Here is the mahogany pattern I carved
    manifold 1.JPG
    Here is the way I made the runner core patterns using plaster and clay
    manifold 3.jpg

    Here are the plaster runner patterns I made from which I made the core molds looking from the bottom of the manifold. It is a 180deg design with two separated paths.
    manifold 4.JPG

    Next step was to make the runner core molds in fiberglass
    manifold 7.JPG

    Here is the final casting. I never got really good pictures of the manifold.
    manifold 10.jpg manifold 11.jpg

    her is the head with the divided Siamese ports. brazed bars on the front, made walls of perforated steel sheet embedded in hi-temp epoxy walls inside.
    manifold 12.jpg

    And the final product.
    Last edited: Aug 25, 2017
    mgtstumpy, j-jock and Stueeee like this.
  8. blue88coupe
    Joined: Jul 16, 2011
    Posts: 11

    from TX

    Dude.... badass. That core for the intake is insane. How many hours do you have in that? I'm not even sure how you came up with the core pattern yet, I'll probably have to study it for a couple hours lol.

    That hilborn deal... how come you didnt use the flange you made(never mind i see the flange bolts to the scooop!)? The crower 8 port style is on my list of things to try and make later. They all seem to use a blower top flange though. So to do it without a blower im thinking of an intake with a blower top in it or maybe adapting it to a tunnel ram that you can take the top off of. Like one of those old weiand 2 piece intakes, take the top off, cast another top that bolts to the weiand but has a blower flange instead of a carb / 2 carbs and then putting one of these hillborn/crower tops on it. I think that would look badass.

    Also on the hilborn mold... how did you get them so uniform and smooth? That pattern looks flawless and perfectly symmetrical! If you got any more pictures of how you build up that pattern I'd love to see them.
  9. Thanx for the kudos. I never figure $$ or hours for my projects. This is my shrink so I don't care as long as the money doesn't run out! Have you seen the fake tall injector stacks that Don Garlits sells? They are pretty convincing and fit over a standard 4bbl carb. Event he big guys do cheesy fake stuff so I don't feel too bad!

    The intake manifold is a bit complicated, I wanted long, equal length runners for street torque, thus the tortuous path, especially for the two middle ones.

    That Hilborn mold was assembled really carefully to the base board (3/4" plywood) so both the cope and drag could be formed over it and they would like up. There are matching 1" dowel rods and holes on that board, and the cope and drag so everything lines up perfectly for the casting using that single half-pattern. It has the outer surface of the body and core prints on either end so the cores I made in the ABS tube would drop snugly into them. To make it I just cut some ABS pipe in half and glued it to the board, glued on a piece of thin plywood for the top flange and I think those are bondo ends I mande in the core tube and glued to the board. I formed fillets with finger and bondo. Got it smooth like you would a car paint job; primer, lots of sanding to fine finish, finally a couple coats of good rattle can gloss enamel. As you can see I used gold color which is what I had on the shelf at the time!
    j-jock likes this.
  10. blue88coupe
    Joined: Jul 16, 2011
    Posts: 11

    from TX

    Not too sure about that hilborn over edelbrock carb deal! :D

    The ABS tube is a fantastic idea. I'm sure getting everything centered so it would flip for cope and drag took some time. I'm gonna try that when I get that far. Thanks again for your replies the stuff you've shown in this thread is extremely inspiring!
  11. It's pretty easy to do. Drill your indexing holes in the base plate, put a dowel in one then carefully draw indexing lines on the board and your half pattern. Glue the sucker down perfectly centered based on your layout lines and you will be pleased how good the resulting cope and drag match up. Each of those of course have precisely the same measurements as the base board with precisely the same 1" hole and pin on opposite ends.I did my casting probably 20 years ago so don't remember the details but I am pretty sure it came out so well I could barely see a parting line. You can do it.

    I split one side of the ABS core box and used the clamp shown to pack the sand, then released the clamp and the pipe sprung open slightly releasing the core.

    I couldn't use a flat match-plate for the intake manifold obviously so I made this one from fiberglass with a white gel coat.
    manifold 8.JPG manifold 9.JPG

    I don't have any other pictures of these projects, wasn't into the picture shooting phase back then.
    Last edited: Aug 25, 2017
    j-jock and mgtstumpy like this.
  12. blue88coupe
    Joined: Jul 16, 2011
    Posts: 11

    from TX

    Lots of bondo and sanding today
    Sitting on an old intake a guy at one of our swap meets traded me.... not too big on the intake but he wanted some motor mounts that i had for sale so we worked it out

    Drew up a throttle linkage and traced it out onto some wood. Gonna be a 3/8" shaft like everything else
    Gonna cast 5 at a time since they're so small... maybe I'll get one that works
    Roughed the center of the core box on the shopsmith band saw
    This part sucked since the hole saw is only so deep, I'd cut down then cut the inside section with a Dremel to help and then chisel out the meat and then hit it with the hole saw again till i made it all the way through
    Finally made it, inside is pretty rough
    This is where I'll end the day, bondo'ed the core box inside and put a couple coats of primer on the pattern I'll probably spend the weekend fine sanding everything down. Its starting to look legit though, we'll see how it goes

    I saw a badass crower injection system on one of the sale sites im on today... Scooped up a couple pics for later days
    mgtstumpy and willys36 like this.

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