Dual stromberg delta airbox wing nuts

I need the 2 wing nuts that attach the carb trumpet baseplate to the delta airbox on my Series 1.5 OTS, so I ordered p/n C12734 from one of the usuals. Not cheap considering we’re talking about wing nuts, but I prefer the look of the larger English style vs the smallish ones I could probably find at a local h/w store.

They arrived yesterday, and they don’t fit. Can anyone tell me if I have the wrong p/n for my application, or if it’s a known issue that the ones available today are known to not fit?

The threaded stud on the delta airbox is 5/16-24. I verified that with a nut from the carb-to-intake manifold attachment, which fits the airbox stud and is of that measure. The wing nut is apparently a metric thread, and it fits nicely on a M8x1.25 test stud -

Thanks all!

From what I’ve seen, you ordered the right part number. For example:

I’d say the seller you used made a mistake. At $8.34 to $13.50 each from the usuals they darn well ought to be correct. I’d call them, and ask that they send you two proper, wingnuts and if they want the old one’s back to send you a prepaid shipping label.

I also have fancy chrome ones, that look much better, for the postage.

I’ll snap a pic.

The ergonomic offset “wings” work really well, especially for old, arthritic fingers!

Given the low stress of the part in question I’d think you could run a 5/16 NF tap through the wing nuts to make them work fine. They won’t be perfect threads but they’ll certainly hold for that. It’s better than messing up the studs.

That’s what I do with these: works just fine.

Before I started trying to modify a part that’s not fit for purpose I’d contact the vendor and give them the opportunity to correct their error. That also alerts the vendor to a problem that hopefully they don’t share with future customers.

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Prediction, Karnac-style…

“We’ve sold hundreds of those ( :roll_eyes:), and never had a complaint before.”

McMaster sells 5/16-24 in steel and SS. I’ve never found fine thread at any of my local stores


Thanks folks! I plan to give them a call tomorrow to see what’s-what, and I’ll go from there. The bags these were in were labeled with the c12734 part number. I’m wondering - I believe the factory battery hold down (which I don’t have) uses wing nuts too. Does anyone have an idea what thread those are - maybe these are those? On second thought - hard for me to believe metric fasteners came from the factory…

Wigs - I appreciate the offer! I’ll pass for now and see what the company has to say. For the future though, are those pretty chrome ones the UNF thread?

John - the website you linked isn’t where I bought these from, but at least that one stated they wouldn’t be the proper thread. I did see that site before I ordered from the other place, which kinda played into my question/ bewilderment too.


I make them UNF thread…no charge! :slight_smile:

I bought a couple of those wing nuts from Xks a few years ago and they fit perfectly and were pretty close to original looking so correct ones are available.

Oh, I know that. I provided it to show that that more than one vendor says that number is correct for that part. I also checked XKS and SNG, they also show that number for that part.

To enter the world of overkill. You could drill the wingnuts out and tap for a thread repair insert of the proper size. A good project if you happen to be stuck “working” from home and/or have lots of time on your hands. :smile:

Maybe there’s been a run on the correct nut stocks for the respirator/ventilator production ramp-up. Not that I’ve heard CORVID-19 affects your nuts…yet.

Someone did say two cases have been identified at Gaithersburg airport.

Left by a forgetful passenger :slight_smile:

No need: a 5/16"-24 tap thru it works a charm. I do that on the chromies.

I’ll make a video, if anyone wants.

A 5/16" 24 tpi tap would work fine on M8 x1.0 as it is 25.4tpi but an M8x1.25 is only 20 tpi so might be less than ideal.

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I did this about four years ago on my SU plenum. Just have to be careful refitting making sure to pick up the correct thread start.

I talked to the vendor today. The guy on the phone was really surprised to hear about the metric thread. Not much they can do at the moment, with their warehouses closed down, but they did make a note to get in touch with their supplier. Asked me to call back once life returns to normal and things open back up.

This, by far, isn’t holding me up so I can be patient.


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If you are looking for a “factory correct” style for a concourse car, I believe McMaster Carr has them unplated with the correct wing style and 5/16-18 thread. Run a 5/16-24 tap through it and no one will know the difference.

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They have steel in 24 pitch as well I believe

So are my blingy chromies…:wink: