The Stovebolt Site Forums The Shop Area Engine Shop Fuel bowl carburetor fitting

Does anybody know where I can find one of these fuel filter to carburetor fittings? I can get one from the truck shop in Concord but wondering if there is a better place to try first. Would a local hardware store have something like this?

I find almost all of my brass fittings like that at Ace Hardware..

Advance, Auto Zone, and O'Reilly have lots of brass fittings on racks behind the counter so people can't steal them. Ask about them and they'll let you back there to search through them. Whatever I can't get at Ace, I almost always find at one of the chain parts stores.

That should be a standard NPT x compression ferrule fitting for 5/16 OD tubing. Available at about any hardware store or plumbing shop.

Ace is the place

How does the compression thread seal? Those are a straight(non-tapered) thread that would require something more to seal the joint. Or am I missing something in this application, is there a section of 5/16 tube between the filter and carb?

Here's an example of a compression fitting. It doesn't seal on the threads, but with a ferrule inside the nut. The ferrule is the second item from the left in the pic.
As far as whether there's a tubing section between the filter and carb, I don't know, but in order to use that type of fitting on the carb, the filter would need a female thread nut and a tubing stub that's shaped like the ferrule on the end.

Autozone doesn’t have it. Napa doesn’t have it. Ace doesn’t have it. Lowe’s doesn’t have it. 🥴

What sort of fuel filter needs a compression fitting? Not familiar with that sort of setup

Trying to use one of these but having trouble connecting it straight to the carburetor. Need to be able to use an adapter that goes from 1/8 to 5/16 male to male.

My Rochester 2G is 1/8" NPT, my AC filter is 1/8" NPT, should be a simple 1/8"NPT hex nipple. As far as I know, all of them used inverted flare for the hard lines up to the filter. Compression fittings aren't really safe for fuel.

The inline fuel filters I've seen on the vendor sites have female pipe threads on both inlet and outlet. To adapt one to a carb with female pipe threads, you'd just need an mpt x mpt nipple. LINK

Double check the thread size and type. There's no such thing as 5/16 taper pipe threads. Are you looking at the adapter screwed into the Rochester carb? If so, remove that and you'll find the threads in the carb are 1/8 female pipe thread. You can use that on the inlet of the filter and connect your fuel line to it, which as 78buckshot says is an inverted flare.

That fitting is the seat for needle & seat on some Carter carbs. It screws into the carb with a gasket between them. The needle is inside the fitting at back .
It will come with a carb kit or might be available from a carb parts supplier as a needle & seat assembly. The other end is 1/8 in. pipe & the filter will screw onto it.

George

I tried to use a simple 1/8 to 1/8 male and male adapter to connect it straight to the carburetor but when I tried to crank it, gas sprayed out all over the place.

Were both ends of your adapter tapered threads? If one was straight thread, it wouldn't work correctly in a female tapered thread.

Here is what I used.

PastorMatt, the threads are both MNPT, male national pipe thread, looks like 1/8" pipe thread, it's known as a hex nipple. Is the filter a new item, do you think the carburetor threads are damaged? Did the nipple thread in without cross-threading or binding?

Maybe I didn't explain it correctly. The fitting circled in the top photo is part of the Carter carb. It has the inlet needle inside of it. Standard pipe fittings are not going to work.

George

Thank you Wrenchbender for clearing that up, I've not had any experience with 6 cylinder carbs. The Rochester 2G on my 283 is not the same type of inlet.

I’m still super confused. Are you dealing with a Carter or Rochester, PastorMatt?

I just checked both a Rochester C and Carter YF carbs that I have and the inlet threads are definitely 1/8" female NPT. All of the carbs I have just have an inverted flare adapter on them for connecting the fuel line. The Carter needle valve fitting is mounted vertically inside the top of the fuel bowl and has nothing to do with the inlet fitting. It has no threads on one end where the needle goes, just a screwdriver slot. Here's a shot of the YF rebuild instructions from The Carburetor shop that came with my YF rebuild kit.

So PastorMatt, unless your carb inlet fitting has been overtightened so the female tapered threads are too large to seal, that fitting you have (1/8" NPT on both ends) should work to install the filter on the inlet of the carb. If it leaks, put multiple wraps of teflon tape around it (being careful not to get the tape over the ends of the fitting), and carefully tighten it down.

Kevin, I’d agree that any Carter or Rochester I’ve ever had is 1/8 NPT at the inlet. However I do seem to think there’s a version of the B (maybe later ones?) that has a funky and large looking inlet.

Matt - could you post a pic of your carb so we know what you’re looking at?

I’m working with a reproduction of a Rochester B. I think the 1/8 fitting I have should work. It looks like what happened was the filter seal was not sealing right against the bowl.

Thanks! I figure it should work too. I hate use teflon tape because I’ve heard it will break down and can clog the carburetor. Some say to do it like you suggest. Would you advise white teflon or the yellow? Yellow is rated for gas and is thicker I think. I have a roll of yellow in my toolbox.

If you're worried about teflon tape (either white or yellow) clogging things up - very unlikely in my opinion unless you lap it over the leading edge of the fitting, then get some Gasoila pipe dope. But the same caution applies - don't goop it over the leading edge of the fitting.

To add to Kevin’s initial advice about teflon tape, wrap it so it tightens as you thread it in otherwise it unravels and breaks off before you get it tight. In other words, your fitting threads in clockwise, wrap the tape counterclockwise.

PastorMatt, I had to use teflon tape on mine due to the threads in the carburetor being enlarged, I used white teflon so that I could wrap it tightly and it would conform to the fitting very accurately, several wraps to take up the needed diameter. I have not had any leakage nor tape contamination in the carburetor. tighten it only enough to keep it from leaking, you don't' want to split the casting with too much torque.

For many years I have used Permatex No. 2 which is thick, non hardening, oil and gasoline proof they say and comes or came in a tube. I haven't bought any for years so I'm not sure it's still available. I've used it in place of various pipe dopes and tapes. It seems to work well an be permanent. DO NOT use it on potable water applications. There's no reason you couldn't use this in addition to tape. I have.

Be careful about over-tightening the tapered pipe fittings in these delicate castings. They will crack, as in split, from the force of the tapered fitting. Teflon tape greatly reduces the friction as the fitting turns in the casting so you can split the casting well before it seems to be over tight. Be careful.

I also would be reluctant to hang a filter by the MTM fitting off the carb air horn because over time the vibration and road shock can stress the air horn and cause a crack where the fitting goes in. I would suggest plumbing the filter down by the fuel pump where you can support it with some sort of bracket. You'll note that the fuel line that runs behind the thermostat housing is captured in a clip screwed to the housing. That keeps the fuel line itself from vibrating and ruining the carburetor, itself or the fuel pump. It also can serve as a support for the fuel filter you are proposing to mount to the carb. In any case don't leave the clip off. GM didn't spend any money on these things that they didn't have to so I assume it was necessary. The same clip also captured the vacuum line going from the carb to the distributor vacuum advance.

Permatex No. 2 is a good solution. It's still available. I have a tube of it that's been in my tool box for years.

Good suggestions on filter mounting as well.

Would suggest you contact the importer; the thread might be metric.

Good luck.

Jon

NPT threads are pretty much worldwide, but the comment is valid.
Have you seen metric threads on anything that should normally have NPT threads?

Kevin - I have not had one of the imitation Rochester B's here, and won't; they, and ALL other imitations are now permanently banned from our shop.

But a few years ago, had an imitation Carter YF come in with metric threads, at least I think they were metric. At least the screws that Carter used would not fit.

I have suggested this is a problem with these off-shore imitations; there is no available documentation. If it were a real Rochester, someone would be able to determine exactly what it was, and I have original bill-of-material for all of the Rochesters, and could easily look up the part.

This is why I suggested to PastorMatt to try contacting the importer, as the importer might be able to help; the rest of us are simply guessing.

Jon

To anyone who has never before used either Teflon paste or Teflon tape:

Take the quote from 1 Ton Tommy, print it in large bold print, and tape it to your toolbox!

Over the decades, I have recycled (fancy word for scrapped) some really high dollar carburetors (at least a dozen Pontiac GTO tripower carbs) simply because the previous owner (often the guy/gal that sent it to us for restoration) had split the housing. BE CAREFUL! Depending on the state of your health, a wrench may not be necessary, tighten it with your fingers.

To those who use it, I won't try to convince you not to; however, when we were still restoring carbs, one that came in for a restoration estimate with Teflon remnants in the threads automatically got the estimate doubled! Other carb restorers whom I knew did the same!

If the threads in the carb are clean, and the threads on the fitting are clean, NOTHING ELSE IS NEEDED.

Comment was made that tape was used because the tapered threads would no longer tighten. We have fabricated many new oversize fittings for carbs such as these.

Jon

Please enter a photo of this carb. The early model B carbs had the 1/8 in. pipe thread inlet at the front of the carb. The latter ones, about 1960 up had a large fitting on the side of the carb. with a 1 in. hex head to install it. I t had a small fuel filter behind it with a 5/16 inverted female flare threads. This fitting needs a 5/16" tube with an inverted flare nut. If this is what you have you can use a section of 5/16 tube w/an inverted flare nut & flared on both ends. Then you can use fittings with 1/8 in. pipe treads & 5/16 tube on each side of the filter.

George