Holley 4160 fuel inlet thread issue for AN banjo fitting - Chevelle Tech
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post #1 of 8 (permalink) Old Sep 21st, 19, 9:17 PM Thread Starter
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Holley 4160 fuel inlet thread issue for AN banjo fitting

I've had this Holley 4160 O-1850 600 CFM carb for over 20 years on my 350 small block. I want to convert it to a -6 AN banjo fitting. I purchased a 9/16-24 banjo fitting, which was the correct thread size according to everything I could find on the 4160. Well, the new part wouldn't fit! It simply just slides right into the hole, way too small.

I've looked all around and can't find anyone with this issue. Hopefully my photos will help, and someone can tell me what's up here. If I look at a stock 4160 photo online, it looks like there used to be a brass adapter fitting screwed into the fuel location. Mine must be long gone. From what I can figure, the current 90 degree adapter I currently have looks to have 3/8" NPT threads on it...?!

Any ideas on what is up here, or what size banjo fitting I actually need? Or, do I need an adapter here? When I look online at stock 4160 carbs (https://images.holley.com/0-9776_01.jpg), they have a brass adapter screwed in here; mine is long gone. Can't find a replacement part or part number.

Thanks,

Tom
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post #2 of 8 (permalink) Old Sep 21st, 19, 9:54 PM
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Re: Holley 4160 fuel inlet thread issue for AN banjo fitting

Do you have some way to take an internal measurement ? it should be a 7/8-20 Holley fitting (inside size) for that.That's the most common Holley size.
Like this one ?

https://www.summitracing.com/parts/h...waAucfEALw_wcB

Do a search for Holley 7/8-20 inlet fitting you can find something that is less than that one.Or just call Summit I'll bet they have someone who can help you get the right fitting.

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post #3 of 8 (permalink) Old Sep 21st, 19, 10:06 PM
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Re: Holley 4160 fuel inlet thread issue for AN banjo fitting

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Originally Posted by 71350SS View Post
Do you have some way to take an internal measurement ? it should be a 7/8-20 Holley fitting (inside size) for that.That's the most common Holley size.
Like this one ?

https://www.summitracing.com/parts/h...waAucfEALw_wcB

Do a search for Holley 7/8-20 inlet fitting you can find something that is less than that one.Or just call Summit I'll bet they have someone who can help you get the right fitting.
The 7/8-20 is for a dual feed center hung float bowl. He has the size thatís listed for Holley banjo fittings.

Was the package sealed when you got it? What brand is it? Have you compared it to the fitting you removed from the float bowl?

Steve R
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post #4 of 8 (permalink) Old Sep 22nd, 19, 9:31 AM Thread Starter
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Re: Holley 4160 fuel inlet thread issue for AN banjo fitting

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Originally Posted by Steve R View Post
The 7/8-20 is for a dual feed center hung float bowl. He has the size thatís listed for Holley banjo fittings.

Was the package sealed when you got it? What brand is it? Have you compared it to the fitting you removed from the float bowl?

Steve R
Yea, I saw references to the 7/8-20, but like Steve said, that wasn't the right fitting for my carburetor and seems like it would be much too big.

Here's a photo of my old fitting on the right and the new fittings I purchased on the left. Both of those parts on the left were separate parts, both in sealed Russell bags, and both say 9/16. And they do fit together nicely, so I think I have what the labels say.

I measured the outside diameter of the old fitting threads; they are 0.663" (between 5/8" and 11/16") and they do seem to be tapered. The OD of 3/8" NPT pipe threads is 0.675, that's why I mentioned that in the original post. Counting the threads per inch, this fitting has about 9 in the 1/2" that's there, so 18 per inch, which does match the 3/8" NPT. But again, that's just a good guess.

I just put an email into Holley. And I've been rummaging around the Summit website, but no luck yet in finding a banjo fitting. This should be easy!

Tom
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post #5 of 8 (permalink) Old Sep 22nd, 19, 10:34 AM
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Re: Holley 4160 fuel inlet thread issue for AN banjo fitting

Quote:
Originally Posted by Gunn317 View Post
Yea, I saw references to the 7/8-20, but like Steve said, that wasn't the right fitting for my carburetor and seems like it would be much too big.

Here's a photo of my old fitting on the right and the new fittings I purchased on the left. Both of those parts on the left were separate parts, both in sealed Russell bags, and both say 9/16. And they do fit together nicely, so I think I have what the labels say.

I measured the outside diameter of the old fitting threads; they are 0.663" (between 5/8" and 11/16") and they do seem to be tapered. The OD of 3/8" NPT pipe threads is 0.675, that's why I mentioned that in the original post. Counting the threads per inch, this fitting has about 9 in the 1/2" that's there, so 18 per inch, which does match the 3/8" NPT. But again, that's just a good guess.

I just put an email into Holley. And I've been rummaging around the Summit website, but no luck yet in finding a banjo fitting. This should be easy!

Tom
Tom, apparently someone in the past stripped the threads on your primary bowl and resorted to installing a pipe thread (tapered) fitting that is obviously larger than the original. A new primary bowl will fix the problem you are having.
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post #6 of 8 (permalink) Old Sep 22nd, 19, 10:34 AM
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Re: Holley 4160 fuel inlet thread issue for AN banjo fitting

That sure looks like pipe thread. Iíd bet the threads on the bowl were stripped at one time and they used this as a crutch. Iíd replace the bowl.

Steve R
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post #7 of 8 (permalink) Old Sep 22nd, 19, 8:52 PM Thread Starter
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Quote:
Originally Posted by Steve R View Post
That sure looks like pipe thread. I’d bet the threads on the bowl were stripped at one time and they used this as a crutch. I’d replace the bowl.

Steve R
Interesting. So I have owned the carb since new, around 1990. I dont recall stripping it. I do recall (very vaguely) having trouble with finding a fitting to clear the air cleaner back in the day.

But there's no way we could get the current fitting in there, if it was 9/16-24. We would have had to drill it out first. And I know we (my Dad and I) did not do that. Maybe the threads were different in 1990?

In any case the new float bowl is a great idea. I'll look into it.

Thanks, Tom

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post #8 of 8 (permalink) Old Sep 22nd, 19, 8:57 PM
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Re: Holley 4160 fuel inlet thread issue for AN banjo fitting

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Originally Posted by Gunn317 View Post
Maybe the threads were different in 1990?

Those fittings have been the same size since the beginning of time. You guys must have forced the pipe fitting in there for some reason.
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