Quadrajet Fuel Inlet Threads Gaulled

Discussion in 'The Mixing shop.' started by SCamaroSS2000, Aug 22, 2023.

  1. SCamaroSS2000

    SCamaroSS2000 Well-Known Member


    I noticed I was leaking some fuel so I went to change my fuel filter and notice my inlet threads to the Quadrajet are gaulled. The fuel filter housing would twist in for a bit, then you could feel the miss and it would be lose.

    What can I do? I assume tap it but I need to watch for metal shavings. Anything else?


  2. DaWildcat

    DaWildcat Platinum Level Contributor

    Last edited: Aug 22, 2023
  3. SCamaroSS2000

    SCamaroSS2000 Well-Known Member

    Thanks. Unfortunately they are closed. I tried calling them. No luck. Any other options?
  4. Dano

    Dano Platinum Level Contributor

    kenny t likes this.
  5. Waterboy

    Waterboy Mullet Mafia since 6/20

    Dang, I used regular JB Weld on mine easily more than 15 years ago. Still works perfect. No leaks. I put a filter in the rubber line that goes from the frame tube to the fuel pump.
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    One of Cliff's posts,

    The only permanent reliable/effective repair is to install a heli-coil insert, it is stronger than the original material. You do loose a tiny amount of sealing surface for the gasket, but we've never had a problem with them sealing up.

    This repair should only be done by someone highly skilled with the correct equipment to make sure the filter housing is in correct alignment with main body for even contact all the way around the seal.

    Using the expanding fittings is NOT recomended, they can come out, and burn your expensive restoration or Muscle car to the ground. They also swell up the carb and make installing a heli-coil and getting a good seal at the housing more difficult.

    Same thing with oversize fittings, they chew up good material used to seat the heli-coil insert.

    We charge $45 plus shipping for this repair, and have done hundreds of them without any problems. The only carburetors which do NOT take this repair well, are very early 1967 units that have had an expanding fitting in them at any point, as they are extremely thin in this area to start with.

    We can also "spot face" the front of the housing if the seal area is damaged (common problem), and can machine off a small amount of the casting if an expanding fitting has it swelled up to much to get an effective seal at the gasket......Cliff



    TORQUED455 and mitch28 like this.
  7. SCamaroSS2000

    SCamaroSS2000 Well-Known Member

    So, I have that resolved. Helicoil done.

    Now I have a leak at the pump. I bought new stainless line from the carb to the pump. It appears to be going in correctly and it is threading well but I still have a leak. I removed the line yesterday and put on some of the white permatex thread sealer to see if that helps. I still have the leak though as of today. I will keep looking around but I am not sure what else it could be. It doesn't appear to be coming from the rubber inlet hose to the pump. I am looking on line and I am seeing that maybe it is the diaphragm. I see there are weep holes so I am going to see if fuel is leaking from there. The car did sit for about a month so maybe that did something? Any other things to look for?
  8. SCamaroSS2000

    SCamaroSS2000 Well-Known Member

    I did another look and it still seems like it is leaking from that the carb SS line connection to the pump. I did notice that the connection on the pump seems not to be fixed or cast into the pump housing. Am I supposed to be holding that connection which is hex shape while I tighten in the line. Maybe that is my problem?
  9. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    In an inverted flare fitting, the seal is accomplished by the flare and sealing surface. Make sure both surfaces are clean, no nicks or deformities. Make absolutely sure the line is going in straight. Any of these factors will cause a small leak. The threads are not where it seals.
    Max Damage and 1973gs like this.
  10. SCamaroSS2000

    SCamaroSS2000 Well-Known Member

    Thanks. I still have a leak. I tried it again. It appears to be going in straight but I assume it is not. The flare looks fine. I cannot really see inside the fuel pump inlet but maybe I will take a picture and see if that helps. The only think I can think of is that the fuel pump threads are gaulled or something. I unfortunately do not have a lift and I am big guy so it is a nightmare to get under there.

    One thing I have noticed is that when I thread the nut it does not thread in completely. There are some threads showing so maybe the mating of the flare in the line is not 100% on the pump input?
  11. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    The fitting isn't supposed to thread in all the way. It puts pressure on the flare and seat, and as long as they mate correctly, it should seal. The same way the carburetor seals at the opposite end.

    It's a pretty common problem to have a leak if everything isn't right. If originality isn't important to you, convert over to AN fittings at the pump, and at the carburetor. There are a number of ways to do that with adapter fittings. Let me know if you are interested.
  12. SCamaroSS2000

    SCamaroSS2000 Well-Known Member

    Thanks. Sure, I am interested. Do you change the line to something else too or stick with the hard metal line? I am just wondering because the current line just lines up and I would hate to have to try and bend the line or I guess bend a new line from scratch.

    The line to the carb has no issues now. Originally though, that is where I had my leak and what caused me to go to the helicoil per your recommendations. It lines up well.

    I am going to give this route another try first.
  13. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    No, you go to a braided line, or, push lok hose. The AN fittings seal up easily. All you need to are 2 adapter fittings. One at the fuel pump, one at the carburetor,


    Summit has the cheapest price if you don't mind the finish,


    Push Lok hose fittings,



    Then you just make up a braided line or push lok line with female -6AN fittings.
    Last edited: Sep 17, 2023
  14. 1973gs

    1973gs Well-Known Member

    All SS lines, brake, fuel or anything else needs lubricant on the threads and between the fitting and the line. Both fittings should be tightened. Then loosen both fittings a turn or two, wiggle the line around and tighten. SS lines do not need to be tightened any more than steel lines. At this point, if you cranked down the fittings excessively, the threads on the fuel inlet and the fuel pump may be damaged because they are softer than the stainless fittings. If you do this from the start, they will not leak.
  15. SCamaroSS2000

    SCamaroSS2000 Well-Known Member

    Bummer. So if I did damage the pump threads, I have to tap the inlet or replace the pump?

    Would the AN fittings and connection be OK in the fuel pump inlet if the threads are a little gaulled? I will try to lubricating and redoing the hard line first, probably tomorrow. If that doesn't work, I can go the AN line route but still may have an inlet threads issue on the fuel pump.
  16. 1973gs

    1973gs Well-Known Member

    You might be fine. Just try to install the fuel pump fitting first, without installing the fuel filter end. If it goes in fairly easy, leave it loose and install the fuel filter end and then tighten both. If they don't leak, you're good to go.
  17. SCamaroSS2000

    SCamaroSS2000 Well-Known Member

    I think I resolved it. I did not have a leak on startup. I used antiseaze on the threads. I read that it would have been better to use a multipurpose grease or a wax. Oh well, hope I am OK. I was careful to not get it into the flare opening.

    I did the tighten, loosen slightly, jiggle the line, tighten, slightly loosen, jiggle the line like 4 or 5 times. It felt like it was engaged well. The flare and the threads all looked good from my perspective.

    I will start it later, let it sit to operating temp, check for leaks, do a check on the nut tightness. If all good, I will drive around the neighborhood and if that is good, I will do a 30 minute spin....

    Thanks everyone.
    69WILD, 1973gs and DaWildcat like this.
  18. 1973gs

    1973gs Well-Known Member

    Antiseize is what I always use. I use the silver at home and copper at work. Both seem to work fine.
  19. SCamaroSS2000

    SCamaroSS2000 Well-Known Member

    I think I am good to go. I stomped on it a few times and drove for 30 minutes. No issues. I will just check it every day for awhile but i think I am good. One thing though. I had my carb rebuilt when I did the helicoil. Holy cow does it have a sucking in air sound now. It sounded like a vacuum leak but I do not see any open ports or cracked rubber. The carb was over jetted and mismatched rods when I had it. Actually it ran pretty good outside of having some fuel smell right after being parked. Cliff rebuilt it and changed it to stock 1970 350 parameters, so 69 rods, 44B rods. He noticed a few other things too.

    I adjusted the idle speed to 750. I need to get the a vacuum gauge on it for the idle mixture. But other than that, how loud of a sucking noise is normal? I took a video and I can upload. It sounds way more than before but maybe I am forgetting. It had been a month since I ran the car.

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