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The Young One
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Discussion Starter · #63 · (Edited)
So, you can see that I am trying to make the inlets sort of like a bowl / funnel leading into each port.
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I may sharpen the transition between each port for a cleaner cut of the air. But what should I do with the circled yellow portion in the middle? Should I build up metal there and make it a 4 pointed divider? Or should I keep it smooth to facilitate cross flow between ports?
 

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In that center section I’d think a smooth convex rounded off shape would work well. Think about the cigar shape of a submarine hull.
 
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Opeler
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I was working on my Sniper today and notice that there is dado, or circumferential recess around the barrels at the intake plate. Would it be possible to trim the plate, and produce a couple of velocity stacks, maybe in a twist formation (to look awesome), and eventually point the forward with a filter, or sponge filter at the intake side?
 

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So, you can see that I am trying to make the inlets sort of like a bowl / funnel leading into each port. View attachment 444082
I may sharpen the transition between each port for a cleaner cut of the air. But what should I do with the circled yellow portion in the middle? Should I build up metal there and make it a 4 pointed divider? Or should I keep it smooth to facilitate cross flow between ports?
Radiused leading edges work fine. I would not raise that center too high as it may disrupt air/fuel emulsion. It would be different if you had injectors in each runner.
 

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Discussion Starter · #67 · (Edited)
So, while reinstalling the tented torquer intake and Weber carb (so I can drive my Opel GT today!), I measured the thickness of the sprinter exhaust manifold flange ears. They seem to be about 11 mm thick. And the new intake flange was cut out of 1/2” thick aluminum at about 12.7 mm thick.

What is the best practice to deal with the difference?
  1. Machine the new flange down to 11 mm thick
  2. Use a spacer 1/2 washer so that the manifold bolts provide even force across both when torqued?
  3. Ignore the difference (this seems like a bad idea)

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The original flanges on intakes and exhaust manifolds should be 12 mm thick, or .472”.

1/2” thick is close enough that it will work, though admittedly the closer they are to being the same thickness, the better off you are.

I once made an intake flange from scratch (years before I had them water-jet), and I used the material I had laying around. It happened to be 5/8” thick aluminum, so this was my solution. I countersunk the flange at the bolt/washer junction.

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You definitely want those thicknesses to be as close to the same as possible, a mismatch, especially if the exhaust is thicker than the intake, will worsen the chronic Opel flaw of vacuum leaks at the manifolds. It's not so bad if the exhaust leaks a little, but it's very bad if the intake leaks. Considering that machining and milling to correct the mismatch is expensive and difficult to do, using "half washer" shims seems to be the easiest fix to try.
 

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Discussion Starter · #71 · (Edited)
I am still scrounging around in the design space for a little more room in each direction.

7. trim the Holley Sniper air cleaner mount surface to prevent interference with hood latch

I was working on my Sniper today and notice that there is dado, or circumferential recess around the barrels at the intake plate. Would it be possible to trim the plate
Something I am contemplating is trimming the air filter base on the Holley Sniper 2300. It is a 5.125" circular base, and it extends too far towards the firewall. So, I am thinking about making a straight cut at the back of the circle (see red line in photo below) where there are no components underneath and then machining the routed edge to match routed edge of the circle. Below is a picture of where I propose to make the cut and the new routing. I am going to hold off on making the cut until final installation, which is a ways off yet. I still need to either refurbish my gas tank and add the in tank fuel pump, or possibly even weld up a fuel tank out of 5052 1/8" aluminum. I'll start a thread on that if I go in that direction.

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And the Sniper Air Intake Hat for the cold air intake would look something the this initial rough design. It is essentially a loft that goes from the circle with the flat cut line to the round forward facing air inlet pipe.

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I would first print it out of plastic to run through a few iterations to make it fit well, as I usually don't get it right out of the gate. Then, I would make a sand core and cast it out of aluminum in the backyard foundry. Pouring hot metal into the sand mold and ending up with a solid part in front of you minutes later is my favorite and most rewarding part of the design process. It is always fun to have the vision of what is in your head a tangible reality sitting in front of you.
 

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Discussion Starter · #72 ·
I once made an intake flange from scratch (years before I had them water-jet), and I used the material I had laying around. It happened to be 5/8” thick aluminum, so this was my solution. I countersunk the flange at the bolt/washer junction.
Brilliant! That is what I will do. So simple and practical. Thank you!
 

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When I installed a header on my Gt the flange was way thinner that the intake so what my grandpa and I did was weld some small pieces of metal to the header and made a little indent for the bolts. I seems like it was worked pretty good and I have 19 vacuum and it runs amazing.
 

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What are the advantages to this over the 1.9 FI intake? Is it just a matter of simplicity or did the stock set up just not flow for.... 🤔
Anyway, nice build on the intake. I love to see people cast their own parts. Have you considered lost foam casting? Seems perfect for creating rapid prototypes of intakes and such.
This guy does some crazy stuff with lost foam. Figure it's right up your alley 😀
 

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Discussion Starter · #75 · (Edited)
What are the advantages to this over the 1.9 FI intake? Is it just a matter of simplicity or did the stock set up just not flow for.... 🤔
1) The stock Opel GT manifold has some serious flow limitations (you are correct) and would require extensive modifications to overcome.

2) I built a rally bob style tented torquer manifold last summer. Fabulous project (learned to TIG weld, port, flow principles, etc). The gains were great and I wanted more, but had reached point of diminishing returns for that approach.

3) back in the beginning of the thread you will see that Rally Bob had found a lot of airflow ( read horsepower potential) in one of his custom intake fabrications. The aim of this fabrication is to get as much of that flow as possible and fit under the hood of the Opel GT.

4) I want a snappy throttle response and improvements over range of RPMs that unlocks the Opel GTs potential without losing its agility, nimbleness, reliability, drivability.

5) The Slant Draft Intake approach has slow gentle minimal curves and fits under the Opel GT hood. Instead of 2 constrictive 90 degree turns (one at bottom of plenum and one mid runner) it has 1 gentle sweeping curve of maybe 70 degrees. plus, the plenum exits are at the bottom instead of the sides. It is delivering over 50% less pressure drop (flow potential) and can utilize Holley Sniper all in one fuel throttle body injection which enables me to run at an angle and get rid of some carburetor limitations.

6) not sure how the stock 1.9 Opel mechanical FI manifold flows (maybe others have experience and could comment). However, it would require a complex long ECU engine management system install and I like to drive the Opel and am not willing to take it out of commission.

Anyway, nice build on the intake. I love to see people cast their own parts. Have you considered lost foam casting?
I have seen some of this videos. Quite amazing designs, intricacies equipment and results. For me, 3D Printing technique for cope and drag style and casting is the way to go. It is more computer aided design work and I don’t have to hand machine the foam for each iteration (I never get it right first time). This, I have developed a technique that works for me with very limited equipment and expense that I really enjoy. I will be posting some of my approach in another thread abs some of my models here. It is one thing to come up with a cool design for a component, but it gets more interesting, challenging, and complex when the additional constraints of design for manufacturing are taken into consideration. What’s the point of a new design if you can’t make it? It is so rewarding and satisfying to dream something up and make it real!
 

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Discussion Starter · #76 · (Edited)
Before I cast my own intake cap, I am going try to see if I can make this low profile air intake from Spectre work.
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In a SLANT DRAFT configuration, the long smooth curve on the edge goes up in the Opel GT’s tear drop shaped hood bubble. I think that the profile is actually a pretty decent match.
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Discussion Starter · #77 ·
The next steps on the SLANT draft include:
  1. Final fitting of the cast / machines manifold complements. This requires removing carburetor and intake and thus taking car out of commission. So, I will coordinate this with gas tank removal / refurb and installation of the custom in tank fuel pump module
  2. TIG welding the cast aluminum intake runner arms to the machines aluminum head flange
  3. TIG welding Holley 2300 flange to cast aluminum intake runner arms
  4. Iterative porting and flow testing
  5. Adjustment of hood hooks and latch assembly for adequate clearance
  6. Prepping for Holley Sniper EFI install (fuel tank removal and refurbishment, install new fuel supply line, complete in tank fuel pump fabrication and install, etc)
 

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Discussion Starter · #78 ·
New potential twist to project and resolution to under hood tightness. Holley seems to have a 2 barrel Sniper Throttle Body Injection unit called the 2GC that is based on the Rochester 2GC footprint. I actually really Ike the Holley 2300 footprint, but I am struggling to get the air cleaner base to fit under the Opel GT hood.
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Discussion Starter · #80 · (Edited)
Well, I took the Ibeam cross member off of my 12 ton shop press and drilled and tapped it and bolted the intake head flange to it and started TIG welding the runner arms to the head flange tonight! I am not a great welder by any means, but love to learn and make stuff!
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