Fuel Tank Oops Fittings

General Everything Else
1

I am hoping that someone might be able to identify a source for the oops fittings. I could be wrong, but I doubt they are Sonex IP/engineered parts.

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2

I asked Grok AI the very same question. Here is the suggestion Grok provided.

Fabricate Your Own OOPS-Style Fitting (Most Common Builder Approach)

  • Many builders have successfully made equivalents using basic machining or hardware store/lathe work.

  • Basic design (matches Sonex instructions):

    • Internal boss: A short threaded aluminum piece (3/8 NPT male on the outside) with a shoulder and O-ring groove on the tank-side face.

    • External: Large hex nut (or custom plate) that clamps the tank wall against the internal boss via the O-ring.

  • Materials: 6061 aluminum bar stock for the boss; standard nuts/washers.

  • Key dimensions from Sonex docs: Drill hole to ~1" final for the 3/8 NPT version; use a Viton O-ring compatible with 100LL (replacement O-rings were SNX-G01-33).

  • Builders often add a groove for the O-ring on the internal piece and sometimes make a custom spanner or backing plate for better clamping.

  • If you (or a friend/local machine shop) have access to a lathe, this is straightforward and inexpensive. Several forum threads show photos of homemade versions that have held for years.

3

Hi Kevin,

Here is a source for plastic ā€œOops Fittingsā€. Might be worth evaluating.

Bulkhead Fittings.

Edit: They have metal ones too.

BanjoĀ® 316 Stainless Steel Bulkhead Fittings with EPDM Gaskets.

And more from Zoro.
Bulkhead Tank Fitting.

We should be able to find something suitable.

Wes

4

Good find. Could work. Looks like the fittings that Sonex sold had a o-ring vs these that have a thicker rubber piece. Also, Sonex sold them for <$30, and no amount of buying in bulk will get the cost down from $90+ to that price.

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5

I checked my inventory and have 5 of the small !/8ā€ fpt oops fittings that came with my latest project purchase. The builder was a machinist and made these. If anyone needs any of these, let me know.

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6

Hi Ron,

I could use one. I looked back at my build and I did replace all three of the main fittings. One of them ended up with a fuel level probe. So, I need one more. Iā€™ll PM you.

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Wes

7

I know Sonex had a 1/8ā€, 1/4ā€, and 3/8ā€ - I donā€™t even know yet if I need one of each - or what exactly. Bu I would like to get at least one of the 1/8ā€ ones you have. Iā€™ll PM also.

8

HI Kevin,

This might help.

SNX-G02 Fuel Tank Fittings Installation.

Wes.

9

Thanks. It looks to me (if no sight tube is used), it would take (2) 1/8ā€ fittings, and (1) 3/8ā€ fitting. I donā€™t see any reference to a 1/4ā€ fitting - I guess that would be for a custom/extra application.

10

Summit Racingā„¢ Fuel Cell Bulkhead Adapter Fittings SUM-220882B

4.5 out of 5 stars ( 7 )

Part Number: SUM-220882B

$13.99

Summit Racingā„¢ Fuel Cell Bulkhead Adapter Fittings

Fitting, Fuel Cell, Male Bulkhead, -8 AN, Aluminum, Black Anodized, Each
See More Specifications

Various sizes

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11

That looks pretty promising.

12

Those look like they could be an option.

On the positive side, those are AN fittings - better than fuel system applications than the NTP thread fittings that were on the Sonex supplied fittings. Also, those PTFE washers look like they might have a better chance of a leak free seal than the o-ring on the Sonex version.

But ā€¦

  1. How would you tighten the fitting if you canā€™t get to the inside of the tank to hold that inside hex in place? The Sonex supplied version has the flats on the end of the NTP threaded section to hold the whole unit while you tighten the nut.

  2. If there is a way to hold the whole fitting and tighten the nut, what would be the AN equivalent sizing to the 1/8ā€, 1/4ā€, 3/8ā€ Sonex fitting sizes? I found this:

ā€œā€¦ the following NPT Port to AN adapters will provide a common I.D. through hole:
Maximum AN line for NPT port size:
1/4ā€ NPT is compatible with up to -6 AN (3/8ā€ hard line)
3/8ā€ NPT is compatible with up to ā€“8 AN (1/2ā€ hard line) ā€¦ā€

13

Just spitballing here on this question:

  1. Using a crowsfoot wrench with an extension to hold the fitting on the inside of the tank; or
  2. Since AN threads are straight, ā€˜double nuttingā€™ (making sure not to overdo it and stretch the threads at all) after getting the fittingā€™s nut in place.

I wouldnā€™t expect a high torque on the fitting nut itself would be required.

14

Double nutting sounds like a good idea. We could also make a tool that would expand inside the fitting and clamp inside it. I would choose the fitting to match the line and not worry about the Sonex equivalent.

The one thing to consider, you need to drill out all of the original molded fitting. So if you install an AN6 fitting, is the OD big enough?

15

Where thereā€™s a will, thereā€™s a way, but those Summit bulkhead fittings just arenā€™t quite what we need. Close though, and a good thought.
Rusty

16

Ah - just realized that with those Summit fittings, the nut would be on the inside of the tank and the AN treads/fitting/port on the outside. So yeah, that wonā€™t work.

17

I missed that before. I think if we have a good drawing, they would not be hard to make on the lathe.

18

Hi Ron

I definitely need one if any are left.

thanks

19

Kevin, let me know address to ship to and I will check on shipping.

20

Let me know address and I will check on shipping. Looks like 3 will be sold and I will have 2 left.

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