All dual feeds leaking. ANNOYED.

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JamesRR

JamesRR

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Hey there. Recently installed a QFT 750 on my car and can't get the dual feed fuel lines to stop leaking. I have tried 2 different kinds. The cheapo Holley chrome style, and it leaked at the plug for the pressure gauge and leaked where the NPT to hose barb screws into the unit. The got a russell set up and it leaked at the outlet into the bowls as well as the plug for the pressure gauge. I have been told to NOT use teflon tape as it will break down over time. Anyone else have problems like this? This is a very simple thing but its giving me hell. Im considering making my own that has flares all around. NTP fittings seem awful.

Best,
James
:banghead:
 
I never knew you weren't suppose to use PTFE (teflon) tape on those...I always have used PTFE tape on the NPT style connections, no fuel leaks in over 20 years of doing it this way.
 
flyfish said:
I never knew you weren't suppose to use PTFE (teflon) tape on those...I always have used PTFE tape on the NPT style connections, no fuel leaks in over 20 years of doing it this way.
Click to expand...

Im to the point of using it. I don't see how NPT seals without it. Thank you!

J
 
Teflon tape does break down in fuel and when it does it will plug any small hole it happens to get sucked into.

I wouldn't waste my time on an inverted flare type of dual feed, get one that has AN fittings at the bowls. In the long run it will be the better buy.

Sealing NPT with fuel running thru it can be done with PST though it has some caveats, but I prefer to use Hylomar. Hylomar is semi-hardening polyurethane sealant developed by someone tired of dealing with leaking English stuff. I use it on o-rings to aid assembly, I use it on gaskets that I want to be able to take apart and then reuse, and I use it on most things that I'm tired of leaking. It isn't cheap, so I don't use it exclusively.

A word of caution about Hylomar, do not get it on your clothes! It will never come out. Lacquer thinner and a lot of elbow grease will slowly remove it. I was told that either MEK or Acetone works better on it, but I've yet to try either.
 
I know for nitrous setups you are not suppose to use the tape, but they recommend using PTFE paste instead. I think the reasoning was pieces of the tape could come loose and clog or jam a solenoid or something....idk.
 
Same issue, and PST = PTFE paste (or close to it anyway). If you go with the paste you want to leave the first full thread clean of the paste and this isn't always easy to do.
 
ARE you installing the line when the carb is on your motor ? every line Ihave ever installed on duel feed i do it on the bench first,lay it on its side bend the tub were it will fit perfect,i have never seen 1 to this day that did not need a slight bend.that fitting will screw easy and tighten with no leak.
 
You don't use tape on flare fittings at all. The threads don't have a thing to do with sealing. Now on pipe threads, it's a different story. I never heard of tape breaking down. I've used it all my life on regular pipe fittings and never had one problem.
 
I learned the hard way about it and gasoline. Safer to use the PST paste. Wipe the first NPT thread clean, and install.
 
I've had very good luck with this one so far. For the seals to the bowl, I re-used the QuickFuel ones.

aed-60946_xl.jpg


http://www.summitracing.com/parts/aed-60946/overview/
 
Ahhh ,the old days.... A hot rodder's experience learning curve,always included a leaking Holley fuel transfer tube. Old stuff gets bend occasionally, and the hard lines never seat correctly again. Used Teflon tape,never fixed the problem.The above post,brings up a point: You do have float bowl to fitting gaskets?....
 
must be a really bad fitting to leak with only 8# of pressure.use dope or tape ,never had problems with either
 
ntsqd said:
Yea, this. No pipe tape or anything else on the AN threads, only on the NPT threaded plug in the 'T'.
Click to expand...

Got a dual feed from quick fuel. No leaks except from the 1/8" NTP for the pressure gauge. The npt was tapped poorly. A bit off center will only a couple threads on the left side of the port. I have ordered a tee fitting with no pressure gauge port. Hopefully this works. Thank you so much.

J
 
Snake said:
ARE you installing the line when the carb is on your motor ? every line Ihave ever installed on duel feed i do it on the bench first,lay it on its side bend the tub were it will fit perfect,i have never seen 1 to this day that did not need a slight bend.that fitting will screw easy and tighten with no leak.
Click to expand...

I got a set up from quick fuel and I think it will work out. Assembled on the bench and no leaks except for the poorly tapped fuel pressure gauge at the front T. Ordered an AN T with no port and I think this will set me straight! Thank you!
 
Abodybomber said:
Ahhh ,the old days.... A hot rodder's experience learning curve,always included a leaking Holley fuel transfer tube. Old stuff gets bend occasionally, and the hard lines never seat correctly again. Used Teflon tape,never fixed the problem.The above post,brings up a point: You do have float bowl to fitting gaskets?....
Click to expand...

Yes sir! I got a new set up from quick fuel and it is a much better seal. One tiny leak at the port for the pressure gauge. Ordered a Tee with no pressure gauge port. Hopefully I am all set! Thank you!

J
 
had the same issue a few years ago.. a friend said to use teflon tape. i argued for an hour that teflon tape has nothing to do with sealing a flare joint. finally since nothing else was working i used the tape on just the threads and bang no more leak. no idea why. maybe the tape lubed things up just enough to get that little tighter not to leak i really don't know. not i like i didn't clean and lube the threads numerous times before.
 
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