Stripped threads in carburetor
Joe Dackman
I have a 1981 F-150 with 302 motor and automatic transmission. Bought it a
few months ago from a guy whose condo association made him get rid of it.
The fuel filter is the sort that screws into the carburetor. While
replacing it I managed to damage the threads in the carburetor inlet.
What I'm looking for is an inexpensive way to fix the problem, preferably
without removing the carburetor from the vehicle. I don't want to spend a
lot of money on this. The carburetor itself is working OK and I don't want
to replace it if I don't have to. As is the motor will run fine, but there
is a leak from the carb inlet due to the threads being stripped.
Thanks for any suggestions you can offer.
Joe
sdlomi2
"Joe Dackman" <jr...@SPAMimt.net> wrote in message
news:Xns9661C80C3...@216.168.3.44...
prevent leaks. Carefully replace the filter, after winding the tape on the
male threads in the direction such that it tightens the end rather than
loosen it when you screw the filter back in. HTH & good luck, s
LoLo
beats teflon tape 3 to 1
"Joe Dackman" <jr...@SPAMimt.net> wrote in message
news:Xns9661C80C3...@216.168.3.44...
>
>
Mike Romain
Teflon tape is 'not' a sealant, it is only a lubricant allowing you to
tighten a fitting easier and tighter. It will not work on stripped
threads.
Loctite 'might' work if it get a chance to cure before use or a helicoil
thread replacement can work.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's
Kevin Bottorff
news:4294854B...@sympatico.ca:
sorry but wrong. teflon tape is not a lub it is a sealant. it is
developed specificily for pipe threads and is made to seal the thread in
a liquid fitting. use enough wraps and it can sometimes crutch up and
seal buggered up threads if your carefull. it is worth a try. KB
--
ThunderSnake #9 Warn once, shoot twice
460 in the pkup, 460 on the stand for another pkup
and one in the shed for a fun project to yet be decided on
Daniel J. Stern
> teflon tape is not a lub it is a sealant. it is developed specificily
> for pipe threads and is made to seal the thread in a liquid fitting. use
> enough wraps and it can sometimes crutch up and seal buggered up threads
For *water* pipes, yes. The result when you attempt a halfassed "fix"
like wrapping teflon tape around stripped threads in a *water* pipe is
that you have a flood.
The result when you attempt a halfassed "fix" like wrapping teflon tape
around stripped threads in a *gasoline* pipe is you have a fire. Gasoline
dissolves teflon tape in short order.
To the original poster: there are repair fittings available that are
slightly oversized. They cut new threads in the carb body as you thread
them in. NAPA Echlin 2-75, see here:
http://www.napaonline.com/cgi-bin/ncommerce3/ExecMacro/NAPAonline/search_results_product_detail.d2w/report?prrfnbr=23502989&prmenbr=5806&usrcommgrpid=
DS
Mike Romain
I am a plumber..... I have 'never' seen or heard of teflon tape fixing
anything. It only allows you to tighten the fitting tighter so the real
sealing faces have a chance to stay tight.
If liquid is getting down the threads, nothing in my plumbers box short
of solder will hold it.
Threads are not sealing points.
He needs to be able to get the threads tight enough to have the washer
seal the faces of the fitting. Teflon tape will only help finish the
stripping job.
ray
>
> To the original poster: there are repair fittings available that are
> slightly oversized. They cut new threads in the carb body as you thread
> them in. NAPA Echlin 2-75, see here:
> http://www.napaonline.com/cgi-bin/ncommerce3/ExecMacro/NAPAonline/search_results_product_detail.d2w/report?prrfnbr=23502989&prmenbr=5806&usrcommgrpid=
>
> DS
I like that idea less than teflon tape. I had a piece of brass fitting
end up in my carb last year and jam the float open... not a pretty sight.
(It was my own damn fault trying to thread a pipe thread into a flare
fitting at 2am instead of calling it a day...)
Ray
Joe Dackman
news:Pine.GSO.4.58.05...@alumni.engin.umich.edu:
Thank you for the advice. I will get the repair fitting. Have been
unsuccessful with teflon tape on ordinary water pipe fittings in the past,
and certainly would not want to risk it with a carburetor.
Joe
Daniel J. Stern
> > To the original poster: there are repair fittings available that are
> > slightly oversized. They cut new threads in the carb body as you
> > thread them in. NAPA Echlin 2-75, see here:
> > http://www.napaonline.com/cgi-bin/ncommerce3/ExecMacro/NAPAonline/search_results_product_detail.d2w/report?prrfnbr=23502989&prmenbr=5806&usrcommgrpid=
> I like that idea less than teflon tape.
That makes you vs. the rest of the world, which has zero problem with
these repair fittings when they are installed properly.
ray
Is fine by me. I've stopped using bandaid solutions like that - I've
learned there IS enough time to do it right the first time. And
"temporary" solutions have a tendancy to become permanent.
(There are times when bailing wire, hose clamps and duct tape are
acceptable as transmission mounts.)
I'd use the repair kit if I had no other choice, but I'd still be
worried about getting crap in the inlet. I'd be inclined to remove the
carb from the engine and make sure you get EVERY last filing out before
firing it back up. Like I said, I've seen what happens when you get
chunks of brass in the float bowl.
Ray
Comboverfish
Mike Romain wrote:
> He needs to be able to get the threads tight enough to have the washer
> seal the faces of the fitting. Teflon tape will only help finish the
> stripping job.
Perfect answer and explanation, Mike. The *reason* why it is a futile
exercise is key here. And kudos for not suggesting a bad body ground
as the cause for stripped threads! :)
Kidding, kidding!!! I enjoy your posts!
Toyota MDT in MO
Daniel J. Stern
> I'd use the repair kit if I had no other choice, but I'd still be
> worried about getting crap in the inlet. I'd be inclined to remove the
> carb from the engine and make sure you get EVERY last filing out before
> firing it back up.
Well, yeah, duh. That's what's meant by "properly installed".
MisterSkippy
wrote:
Common problem with Fords. Go to your local parts place. I've seen a
repair kit for this in a blister pack on a rack. IIRC, it looked like
a self-tapping oversized thread adapter deal.
FWIW
YMMV
ray
Funny. Unfortunately, I've seen too many people's definition of
"properly installed" or "properly repaired" that is one step above
bailing wire and duct tape. And these were supposedly professionals.
That's why I fix my own car and most other things - I can butcher it for
a lot less money.
(and I'm not talking about just car stuff)
:)
Hugo Schmeisser
> Kevin Bottorff wrote:
> >
> > Mike Romain <rom...@sympatico.ca> wrote in
> > news:4294854B...@sympatico.ca:
> >
> > > sdlomi2 wrote:
> > > >
> > >> "Joe Dackman" <jr...@SPAMimt.net> wrote in message
> > >> news:Xns9661C80C3...@216.168.3.44...
> > >> >
> > >> >
> > >> > I have a 1981 F-150 with 302 motor and automatic transmission.
> > >> > Bought it a few months ago from a guy whose condo association
> > made >> > him get rid of it.
> > >> >
> > >> > The fuel filter is the sort that screws into the carburetor.
> > While >> > replacing it I managed to damage the threads in the
> > carburetor >> > inlet.
> > >> >
> > >> > What I'm looking for is an inexpensive way to fix the problem,
>
> I am a plumber..... I have 'never' seen or heard of teflon tape
> fixing anything. It only allows you to tighten the fitting tighter
> so the real sealing faces have a chance to stay tight.
>
> If liquid is getting down the threads, nothing in my plumbers box
> short of solder will hold it.
>
> Threads are not sealing points.
>
> He needs to be able to get the threads tight enough to have the washer
> seal the faces of the fitting. Teflon tape will only help finish the
> stripping job.
Pardon an ignoramus with an ignorant question:
If the above is true, then what seals air-line fittings? I always had
the idea they sealed on the threads, which is why everyone tells you to
use Teflon tape on them.
Daniel J. Stern
> > Threads are not sealing points.
> Pardon an ignoramus with an ignorant question: If the above is true,
> then what seals air-line fittings? I always had the idea they sealed on
> the threads, which is why everyone tells you to use Teflon tape on them.
You're right. The previous poster's assertion that "threads are not
sealing points" is not always correct. Tapered pipe threads (NPT, for
instance) and certain other thread types (e.g. Dryseal threads) are
sealing threads. I think what the previous poster was trying to convey is
that the threads on e.g. a flare fitting are not sealing threads, which is
correct.
DS
Mike Romain
I realized that as soon as I hit send and was expecting the above.
Daniel is correct, for any fitting with a sealing face or o-ring trying
to seal the threads is a waste of time.
Even with some tapered fittings, teflon isn't allowed by safety code.
Gas pipes need liquid pipe dope and we use it (dope) for hot water
heating pipes.
ray
>
>
> I realized that as soon as I hit send and was expecting the above.
>
> Daniel is correct, for any fitting with a sealing face or o-ring trying
> to seal the threads is a waste of time.
>
> Even with some tapered fittings, teflon isn't allowed by safety code.
> Gas pipes need liquid pipe dope and we use it (dope) for hot water
> heating pipes.
>
> Mike
> 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
> 88 Cherokee 235 BFG AT's
When I installed my nitrous system the instructions told me in no
uncertain terms NOT to use teflon tape on AN style fittings and use
teflon PASTE on pipe thread fittings. (In this case it's to prevent
teflon tape from plugging a nitrous line.)
I find that kind of neat working on cars - there's
fine/coarse/flared/pipe thread fittings - metric/standard, and I'm sure
more. Occasionally that's a pain, but it's still interesting - you
learn all sorts of new skills. :)
Ray
Mike Romain
You are right. That tape can also gall up so the threads don't end up
with a good metal to metal seal. This causes slow leaks eventually when
the built up pieces squash from vibration finally and the fitting comes
loose.
The poster was asking about air line fittings, those are a compression
tapered end if I remember right so the threads have to go on really
tight to seal the metal nipple to the cone. You can ball up enough
teflon tape to make a seal, but it will eventually leak, the least
amount that you can stick on is the best so the metal to metal at the
end tags. It is a lubricant. Teflon over the seal face end will
eventually fail or plug things.
Jeff Wisnia
I hope you will not take this the wrong way Mike, but I can't tell if
you fully appreciate the design principles of different kinds of tapered
pipe threads.
Take a look at the thread form of NPT threads in Machinery's Handbook
and you'll see that the crests of the male and female threads don't come
to a sharp point, but are flattened. The roots of the threads are closer
to a sharp point, so the crests don't fully fill the roots. This is done
on purpose to make sure that the flanks of the threads will contact each
other to support axial loads on the joints.
That flattening of the crests of the threads leaves a small trapezoidal
shaped path spiraling along the full length of properly torqued engaged
threads, sometimes referred to as a "spiral leak path". It's that path
which has to be filled up with some kind of "pipe dope" to keep it from
leaking, and the choice of what dope to use is yours to make, I still
prefer using Rectorseal or a paste type dope for water service.
NPTF threads are what's called "Dryseal" threads. Those threads have a
sharper crest on the male threads and are designed to create a metal to
metal crush seal along the spiraled thread path, without needing any
sealant to keep them from leaking. They are more often found on brass
fittings, where the mallability of the brass makes it easier for the
crush seal to occur.
The last letter in NPTF, the "F" stands for "fuel". When the thread form
was originally developed it wasn't easy to find pipe dopes which would
withstand fuels, to a thread which would seal without and dope was
designed.
A few lines swiped from Machinery's Handbook which describing NPTF
threads are:
+++++++++++++++++++++++++++++++++++++++++++++++++++
American National Standard Dryseal Pipe Threads for Pressure-Tight Joints.
Dryseal pipe threads are based on the USA (American) pipe thread;
however, they differ in that they are designed to seal pressure-tight
joints without the necessity of using sealing compounds. To accomplish
this, some modification of thread form and greater accuracy in
manufacture is required. The roots of both the external and internal
threads are truncated slightly more than the crests, i.e., roots have
wider flats than crests so that metal-to-metal contact occurs at the
crests and roots coincident with, or prior to, flank contact. Thus, as
the threads are assembled by wrenching, the roots of the threads crush
the sharper crests of the mating threads. This sealing action at both
major and minor diameters tends to prevent spiral leakage and makes the
joints pressure-tight without the necessity of using sealing compound.
+++++++++++++++++++++++++++++++++++++++++++++++++++++
All that's well and good if male and female threads are manufactured to
specs, something that doesn't always happen, particularly with some of
the cheap imported junk we're seeing nowadays.
And, I do agree with some of the things you have to say about teflon
tape as a sealing material for NPT threads. It's not always easy to make
sure the teflon squishes where it should go to completely fill the
spiral leak path. And backing off a joint a bit after proper tightening
and then retightening it can displace the teflon so the joint won't
seal. That generally doesen;y happen with paste type dopes while they
are still "fresh".
Jeff
--
Jeffry Wisnia
(W1BSV + Brass Rat '57 EE)
"Truth exists; only falsehood has to be invented."