Pipe thread and fittings questions

Big_B · Jul 17, 2007

I am finding out that I don't know jack about pipe threads and fittings, so hopefully someone can lend some insight into this. How do I figure out what size I need for the following applications?

Problem 1: I am trying to find a fitting that screws into the fuel pump and gives me a nipple to run a 3/8" fuel line (hose) to the carb. (Ditching the old steel line) I found one at Napa that looks just like the old fitting on the steel line, but it won't thread in.

Problem 2: I need a T fitting on the oil pressure extension so I can run the stock guage/sender and an aftermarket mechanical guage.

Problem 3: I can't get the old heater hose fitting out of the old manifold, and the only one I can find is a 2.5" tall monstrosity that looks horrible. What size is this fitting?

Can you usually find these things in the plumbing section at your local Ace/Lowes/Home Despot?
What else do I need to know? (NPS/NPT?)
Should I use some kind of pipe dope?

RogerC62 · Jul 17, 2007

Pipe thread size is based on the ID of the hole through the fitting or pipe and not the thread itself.

The fuel line may be straight thread. I've found the easiest thing to do is take the old line/fitting/or component with you to match the thread for what you need. The best place to get your fittings is a hydraulic supply store such as Parker or Lenz or possibly a farm supply store.

enferno · Jul 17, 2007

if memory serves, you cannot run a T fitting on the oil pressure and run both the stock + a mech. after market. when you add the T, i think it lowers the reading for the pressure.

i could be wrong though.

BullittStangV8 · Jul 17, 2007

I think you can run a T for the oil pressure, since the pressure on both fittings should be equal? I dunno, its been a while since ive taken physics.
Summit racing has allot of fittings, and the brass section i homedepot has some stuff as well.

D.Hearne · Jul 17, 2007

I've run a "TEE" on the oil line many times and the pressure is no different. The Oil pressure port is 1/4" or 3/8"NPT (National Pipe Thread) Intake heater hose can be either 3/8" or 1/2" NPT. The Fuel pump fittings are also likely pipe thread and can be anything from 1/4" to 1/2" NPT. All this stuff can be sourced at most hardware stores or parts houses in steel, brass or stainless. Heater hose fittings are also available locally thru your parts house. One vendor is Four Seasons, a look in their catalog at your parts house and you'll find what you're looking for.

enferno · Jul 18, 2007

i stand corrected then.

Jester67 · Jul 18, 2007

You can use Teflon tape or a pipe adhesive on the fittings. I would recommend Loctite/ permitex 567 it is high temperature high pressure oil resistant thread sealant that will work with all metals it is good for 1500psig instantly and 10000psig after a 24hour cure. 565 is almost as good but you must have at least one of the connectors copper based. I like the adhesives because unlike Teflon witch is a thread jammer it is an adhesive that is vibration resistance and is not affected by temperature variations. If you do use Teflon remember that the NRC states that no more than 3 turns of tape may be applied to any joint.

Big_B · Jul 18, 2007

Lots of good info, thanks all.

I was able to build a T using brass pipe fittings from Lowes, as <b>D.Hearne</b> states it was 3/8".

One of the interesting things I found out was that there are three different kinds of fittings (that Lowes stocks anyway) - Compression, Flare, and pipe thread. The heater (intake manifold) and oil pressure sending unit are pipe threads (NPT?), but the fuel pump is a 5/16 compression, and they didn't stock a barbed 5/16 compression fitting at my Lowes.

Thanks again.

D.Hearne · Jul 18, 2007

Jester67 said:
If you do use Teflon remember that the NRC states that no more than 3 turns of tape may be applied to any joint.

NRC ? Ok let us in on your build up secret.............................. We going for a Nuke supercharger or somethin here?

TOM B · Jul 18, 2007

NOTICE!!!!! When you use a sealant on the threads and you should, be sure its (thread sealant) and not thread locker!
do not use thread tape which is not recomended for any kind of sensor because it will clog up the sensor and maybe something worse.
When you use a sealer, start the sealant about 2 threads back so as to keep the sealant away from the sensor hole and never back it out or you will have to replace the sealant, get it at the right place the first time.

9and not

Jester67 · Jul 19, 2007

D.Hearne said:
NRC ? Ok let us in on your build up secret.............................. We going for a Nuke supercharger or somethin here?

My new Flux Capacitor is almost complete. I will see you guys Yesterday.

Jester67 · Jul 19, 2007

TOM B said:
NOTICE!!!!! When you use a sealant on the threads and you should, be sure its (thread sealant) and not thread locker!
do not use thread tape which is not recomended for any kind of sensor because it will clog up the sensor and maybe something worse.
When you use a sealer, start the sealant about 2 threads back so as to keep the sealant away from the sensor hole and never back it out or you will have to replace the sealant, get it at the right place the first time.
9and not

Good advise that is also how I apply it.
And no need to over apply two threads level with the major diameter is all that you will need.

D.Hearne · Jul 19, 2007

I do it the easy way, just use pipe thread sealer.(Teflon Paste) My computer just blinked...............was that you Jester?

Jester67 · Jul 20, 2007

Teflon pipe dope is not a good material to use in this environment because of the temperature and pressure. Because of the lack of a binder it has a tendency to creep over time and fail.

Nah but it might have been something I designed.

D.Hearne · Jul 20, 2007

I've been using the paste for years now and had no failures. It's a tad messier than the tape, but far easier to use. I always hated screwing with the damn tape.

Jester67 · Jul 20, 2007

D.Hearne said:
I've been using the paste for years now and had no failures. It's a tad messier than the tape, but far easier to use. I always hated screwing with the damn tape.

The loctite is messy as well but well worth the trouble I have never liked the tape.

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