I recently repaired the center carb on a 70 Cuda so I replaced the metal fuel lines with a repro set. I decided to use the original brass fuel blocks because the repro didn't look correct. After tightening and re-tightening all the fittings from the carbs to the fuel blocks, they are still leaking. Is there a lube or trick to prevent the fittings from leaking gas?

If stainless lines you need to cinch them and loosen them multiple times. I have even seen that on plain steel lines. Each time you tighten them go a tad tighter. I just went through this again on my maxwedge lines.

Hi Glenn,
This is what you do. Permatex makes a high temp sealant # 59235.
Use this it works. Let it dry for at least a day or two before you run it with gas.
Bob

Pretty sure they are flare fittings, in which case sealant is useless.

Flare a piece of 5/16" copper tubing,cut off the flare,insert in fuel inlet fitting and no more leaks.

I ran into that issue last year when I was putting my T/A together.
My lines were leaking like crazy at the carbs, and nothing seemed to help, until my engine builder told me to put some grease on the threads before installing the lines. I never thought that would work, but was running out of ideas.
Greased the threads up with red grease, installed and tightened them, fired up the engine, and dry as a bone!

The seal takes place between the inverted tubing flare and the corresponding "male" flare in the fitting.

If you have done the "loosen / tighten" routine more than 3 or more times, 1. Either the flare on the tube is bad,
2. The nut is bad,
3. The "seat" in the fitting is bad,
4. Or there is debris preventing the seal.

Disassemble, inspect the flare on the tube and seat in the fitting. Your problem should become apparent.

I'll use either a teflon paste or grease to lube the threads so that they help seat the flare and prevent galling of the threads, using a tube wrench instead of a "regular" wrench will also prevent you from "egging" the flare nut causing leaks by making it harder to fully seat the tube nut sealing the flare, stainless or steel

In spite of all the naysayers,,,,,teflon tape has always been my go to fix for leaky fuel lines. Has worked perfectly on my six pack. Be certain to use correctly and not allow any into fuel line tubing.

Thanks for all the Trouble shooting ideas!

Glenn, where did your get that trouble shooting trophy? I was in the 1969 Chrysler/Plymouth contest in New York.
Bob

Grease or oil is best and should always be used on flare fittings to allow you to get them tight.

IMO never use teflon tape anywhere on a fuel system, never. Because it is near impossible to get all the little pieces out when you take it apart. Plus it looks like sh!t and tells everyone you don't understand flare fittings.

AMEN!

Joe

Since theres inverted flares on these , the threads dont
Really hold any pressure
Listen to Mr Bill 62 maxwagon
This is the proper way - if you cant titen them properly

Generally the use of copper is avoided with gasoline use, as the gasoline with slowly dissolution the copper and actually "plate" the fuel system/carbs/etc with copper thru an electroless process

not to mention you have now doubled the sealing surfaces and potential for leaks

Not really,neither of these have leaked with stainless lines since I finished them,the bird in 92 and the other in 2011,both have been apart numerous times,put the lines on and never had a leak problem and I have yet to see any sign of copper plating anywhere.You do as you see fit,I'll stick with what works for me!

Show me the time lapse results of the dissolution
of copper when used with gasoline.
There would be a fraction of a zillionth of an inch
exposed on a flare . I m o
These arent space shuttles ..
if you really want ---use a torque wrench on them
And adjust to 29 neuton meters .

I suppose you might still even have some electrolysis
occuring when brass meets steel - if you dont use a non
Conducive type gasket.

Im with the ol timer - use what works ..
lol - im only here to argue

Wow those are kool where can one get them?

I will provide my solution to the "leaking lines" on a 6-pack. I resorted to using a small black O-ring that was just small enough to fit inside the Carburetor nut (it the same diameter as the flared fuel line) that the fuel line bolts to. Because the O-ring is actually sealing against the fuel line "flare" and the Carb nut, you can't tighten it real tight like you normally would or it will destroy the O-ring. I tightened it "extra snug". I did this as a "last resort" when I couldn't get my new lines to seal. It has been 2 years since this fix and I haven't had to touch them and they are not leaking.

Posted above by 62maxwgn

Flare a piece of 5/16" copper tubing,cut off the flare,insert in fuel inlet fitting and no more leaks.

I have used this method for 20+ years. Sounds wrong, but it works. I can't explain why it works except for the lubrication properties. A dab, not a blob, on the threads and flare. I didn't believe it when I was told either. One night as a last resort I tried it. Made a believer out of me. No leaks ever.
Doug

Google flare washers

I tried thread greasing on my six pack lines, still had 2 fitting that leaked. Perhaps fittings are a bit worn as must undo them each time I wish to remove carbs. Any six pack owner understands this dilemma. Teflon tape relieved immediately.

Have never a problem easily removing it.

As I happen to use an use an air cleaner, impossible to see any teflon tape on fittings.

Leaking fuel lines are a more certain sign that someone does not know what they are they are doing,,,,not to mention the risk of burning the vehicle down.

To each their own

Typical moparts...the experts weigh in with good advice and you guys kick them with your cave man automotive fixes and opinions. The only reason I am even attempting to help the uninformed is to keep you guys from giving the six pak more negative internet BS. We give you a "procedure" [tuning guide] and you can't even take the time to read it, but you come on here & expect one of us to just give you that quick answer to the quick question. For free no less.

When you install 6 pak fuel lines all the lines need to be installed together and tightened simultaneously. The lines are leaking because the flare end is not seating against the seat on the fitting. DOH!! Teflon tape on the threads does not seal anything. Lubricating the nut threads and the between the nut and tube will allow the nut to turn and not grab the tube when tightening. You need QUALITY flare wrenches as well.

A properly tuned six pak will outrun it's 4bbl equal...

Well said, and I am beginning to ask why I even try

I am well aware of the sealing mechanism of how flared fuel lines do their business.

Again I repeat that I have had circumstances where lubrication of threads(this is not exactly new science in automotive repairs,,,every Model T shade tree mechanic understood this) has not resolved a leak, where teflon tape has.

Have any of the experts considered the possibility that perhaps the teflon tape itself serves the purpose of lubrication of the threads more effectively than mere oil or grease that gets squished out of the threads because of the intense pressure generated per square inch as the fitting is increasingly tightened,,,,whereas the structure of the tape's chemistry maintains its lubricating capabilities no matter how much pressure is generated?

I thought not! I do not necessarily subscribe to my anecdotal guess on this,,,perhaps one of our members with expertise in this science might chime in.

I have already agreed that perhaps effectiveness of my fittings and/or line flares may be below perfection.

As an aside as a six pack owner,,,,I have several times referred to and read well the "white" paper on six pack tuning,,,,still does not make me an expert, just as I am not on Rochester fuel injections with which I am familiar,,,but have learned much of value,,,just as reading many great books on tennis or golf does not make us great players. However cannot remember ever reading a single one of those books where the reader was belittled as not ready to go on the tour because they are not as expert as the author.

Yea teflon tape provides lubrication and anti seize properties.

But like I said above it leaves many pieces of tape inside the fittings when removed and is not good to use around auto fuel systems.

And teflon tape in this case provides no lubrication between the sleeve nut and the back of the flare where it is needed most like pointed out above. Got to read what is posted.

Grease or oil has no harmful effects to the fuel system if it gets inside.

And yes tubing wrenches are used, didn't even think I had to point that out since it was posted above already.

I do not use copper flare washers but can understand how they might be beneficial in some cases. But they reduce the thread engagement if used and doubles the places for it to leak like pointed out above.

Type R copper would be best because it is thinner than type L soft copper tubing.

Would I buy them somewhere? No

This how you make them like what was said above. That groove in your tubing cutter is for cutting off the least amount of tubing if your tubing is flared already. Not really for making flare washers.


The only time I have put something between my flare fittings is a cone screen to protect against dirt, not to help seal it.

I'll throw in my I can't find where the original poster said he was using stainless or steel lines. The corrective action is the same regardless. If the fittings are leaking, unless the machining on the fittings is poor, the tubing flare is defective in some way. Otherwise the fitting wouldn't be leaking. I have a selection of stainless steel female fittings and with a GOOD tubing wrench and lubrication on the nut, I tighten the bejesus out of them. This re-forms the flare on the tubing so it will seal. Never failed me yet. As a note, I've only used stainless lines one time (brakes) and never again. I had to tighten them so tight to stop them from leaking I was afraid I would either strip the fitting or gall it. Again, just my , feel free to do whatever turns your individual crank.

I know about stainless lines, they are hard as heck and hard to get sealed.
But not only that, but since you have to tighten them so tight the first time, the second time could be even tougher to get them to seal because the seat is indented from the hard stainless and sometimes they don't go back together exactly the same as the first time.

Mild steel on brass is the best sealing combo and longest lasting imo.

Stainless is more prone to cracking because it is so hard.

Tom q always told me to lube fittings
I guess thats common sense.
At a semi last resort copper washers are a fix

A friend had the same problem on his 440 Challenger, took a while but I plumbed the miserable thing with braided stainless. Kept it all close and short as possible.

Ed

One more vote for putting some lube on the fittings. I had the same problem and was amazed at how easily this solved it.

And bumblebees can't fly!

I've used teflon tape numerous times when R&Ring carbs. Has never failed me. . Using red engine assembly grease, have found been unable to guarantee no leaks,,,possibly unless I am willing to tighten ferrules tighter than I deem safe.

Have often used in other applications over my many years as is recommended, but at a few times of memory tape has been my go to solution for recalcitrant leaks.

Always cautious to ensure that tape not find its way into undesired areas, understanding the implications.

If it did not work for me, I certainly would be unable to use the car and would be forced to buy a replacement fuel line system or devise another solution.

There is a reason inline tube dumped about 500 sets of these lines in the last year.

Not sure what you paid but when they first dumped them it was the upper and lower for like 254 shipped, I bought a few, a little time has passed and the flippers are 3-4x the price.

But it doesnt seem they were a big seller for inline or maybe they just decided to rid themselves of a headache.

Id bet you have the ss ones from inline vs like the mopar performance ones.

I read online that duct tape works better than teflon

If you read it online then it must be true.

Reading your posting reminded me that I too likely have stainless repro's that is the root to my unique difficultly in ensuring a good seal. And the comments from others posting reminded me of the problems caused by using stainless tubing with braking systems,,,which I have on my 59 Vette with disc brakes which has always been a problem with only one caliper. It is generally believed by many that stainless brake lines can be a real bear and strongly advise usage. No reason why the same could apply to fuel lines. Likely why the copper solution as recommended by earlier postings has worked well, as copper and even steel are far more malleable than stainless and will conform and accommodate idiosyncratic fittings better.

When first installed on my Six Pack, I experienced no leaks. It was only subsequent R&R's where I had problems. The first time seal likely made male and female 'conform' but subsequent R&R's were unable no matter how tightly cinched were unable to undo the original 'set' and adjust to a new set as female and male matings were not exactly the same,,,,even though I would carefully before tightening of ferrules 'wiggle' fuel lines within them about as I tighten them to ensure an exact mating. Yes I do use only the correct flare wrenches.

The next time I have fuel lines removed, I will examine very closely brass connectors and lines.

Using a magnet, I just now checked the lines and ferrules on the theory that some stainless, not all is magnetic just as regular steel. Lines and ferrules both are magnetic so still do not know if steel or magnetic stainless. However as brass is likely softer than either, will be curious to find if any damage preventing proper mating is in the brass fitting itself. Again copper being softer than steel or stainless it could conform to brass and accommodate ok.

The advice on greasing behind the flare on the line is well taken,,,,even when using my teflon tape approach. When using the lubricant approach I do lube this area,,,,but have been negligent in doing so when forced to teflon solution.

I forgot to suggest the most likely cause of sealing difficulties with fuel lines. Ma Mopar required a quality product that could be R&R'd many times over the life of the car.

Is there anyone that assumes that offshore manufacturers give any consideration to this critical requirement when designing or building their third rate products!

I've used for the last several plus decades, the HS/DC/Mopar Performance, Right Stuff, Fine Lines, In-Line tube Steel and Stainless six pack lines, I use Stainless fuel/brake/emission/etc lines almost exclusively in my customers and personal builds....ZERO LEAKS, ZERO ISSUES, most problems can be traced to, and are usually operator/installation ignorance and or error

Hey DC, try the duct tape, it really does work,