Speedster fuel line: Fuel Bulb threads for the outlet are 1/2-18: What is that used for in modern times ?

[FireDan]

First off, this is not a debate of whether or not to use an inline fuel filter : that argument has been beat into the ground by both sides pro and con ......

This is about a modern safe fuel line for a Speedster where safety is more important than originality . And yes, Henry's system worked as well as it was designed to , but as a Firefighter for 20 plus years who has been on his share of vehicle fires , well, I will say no more .

The Fuel Bulb threads for the outlet are 1/2-18 straight thread where the FORD compression type fitting screws onto the bulb with the felt compression material. 1/2-18 does not seem to be a common thread for much that I can figure out, yet there are 1/2-18 UN taps made and sold .

What is that thread size used for in modern times ?

I am making an adapter out of a piece of 1" x 1-3/4 long brass rod , 5/16 hole drilled through , then tapped 1/2-18 on one end , and 1/8 Pipe on the other end , so I can screw it on my fuel bulb with a 1/8 Pipe x 5/16 Barb 90 degree and use 5/16 rubber fuel line , a 5/16 inline Fuel filter ( let's not argue the merits or not of that ), then onto 5/16 steel line with bubble flares to slip the rubber fuel line on, and at the carb a 5/16 double barb fuel shut off into a 5/16 barb x 1/8 pipe 90 degree......

the reason is , A) need to replace the old nasty copper line B) Not keen on the felt packing, or using a section of rubber hose as a packing material , brass compression ferrules don't belong there , C) 5/16 line and 1/8 Pipe fittings are all 5/16 internal diameter which is better flow that 1/4 inch fuel line , which May or May not have bearing on whether or not an inline fuel filter will or will not starve a Model t of fuel .

By Putting the fuel filter at the top , more head pressure , gravity flow , maybe yes, maybe no ?

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[FireDan]

Found this thread / fittings chart , a lot of information , I did not see 1/2-18 listed there for anything .

https://www.essentracomponents.com/en-u ... ectors#npt

According to Royce and the late Stan Howe, it IS 1/2-18 at the fuel bulb ........
"
By Stan Howe Helena, Montana on Wednesday, February 22, 2017 - 02:58 pm:
It is not straight pipe nps, it is 1 2 x 18. Royce is right."

I checked Whitworth threads , It's not Whitworth: Whitworth is 1/2-12. I did find this relating to 1/2-18 threads:

Dryseal Fine Taper Thread Series, F-PTF: The need for finer pitches for nominal pipe sizes has brought into use applications of 27 threads per inch to 1⁄4- and 3⁄8-inch pipe sizes. There may be other needs that require finer pitches for larger pipe sizes. It is recommended that the existing threads per inch be applied to the next larger pipe size for a fine thread series, thus: 1⁄4-27, 3⁄8-27, 1⁄2-18, 3⁄4-18, 1-14, 1 1⁄4-14, 1 1⁄2-14, and 2-14. This series applies to external and internal threads of full length and is suitable for applications where threads finer than NPTF are required.

https://www.thomasnet.com/articles/cust ... e-threads/


Everything you ever wanted to know about Dry Seal thread types, but were afraid to ask :

https://pppars.com/wp-content/uploads/2 ... 3-1976.pdf


5/16 tubing uses 1/2-20 and 1/2-24 depending on what type of flare:

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[FireDan]

I will post this here too: Thread and end connection Identification Guide. It did not show anything that was 1/2-18 but it is a wealth of information for thread types and fittings, whether you will ever use them on a Model T or not ....

https://www.swagelok.com/downloads/webc ... -13-77.pdf

[FireDan]

Here's something that is 1/2-18 , and guess who used it (again)? would you believe :
"Anybody know a supplier who has nuts to fit the 1/2-18 threads on back of the 36 Ford rumble seat pads -- or who supplies a tap that size so someone could fabricate the nut?"

It's starting to remind me of an Alfred Hitchcock movie: You know he's going to turn up in his own movie somewhere, you just have no idea where .

Still have not answered my own question of "What is 1/2-18 used for in modern times "?

[Dan Hatch]

https://www.victornet.com/flypage.html

Try here. Dan

[Scott_Conger]

You've made a bunch of declarations and followed up basically with "don't question me on this", so there really is no point in offering any suggestions from experience. Instead, I'll offer 2 statements and a question:

S1: 1/2-18 is the thread used universally for liquid fuel lines on cars of the period, along with flared fittings on carbs for larger cars. As for modern applications for that particular thread, I have never seen one, but that doesn't mean they don't exist.

S2: If you use a 5/16 line, you are still trying to dribble it past a too-small hole in the float valve (assuming you are using an NH)...you could hook up a fire hose to it and not get more fuel than can be delivered by a correct 1/4" line. One small constriction will undo any manner of changes performed elsewhere short of increasing delivery pressure (and that is not necessary). There is a solution to that restriction, but that is not what is being asked in this thread so there is no point in going there.

Q1: Do rubber hoses and plastic fittings belong anywhere on a gravity feed fuel system?

Now, for the benefit of anyone who is interested in these things, below is a reproduction of a factory adapter to adapt a Model T to an accessory carb Zenith S4BF...where both 1/2-18 as well as flared fittings are involved:

[Jerry VanOoteghem]

Q1: Do rubber hoses and plastic fittings belong anywhere on a gravity feed fuel system?

Not on my car!

A nice runabout burned up several years ago on an MFTCI Int'l. Tour, due to a failed rubber fuel line. Several fire extinguishers were emptied on the blaze to no avail. The 90-year-old driver got out with singed ankles.

[Dan Haynes]

I agree with Scott.

[DHort]

1. What type of carburetor are you using? Does it need a larger fuel line for that carb? Stromberg OF does fine with Henry's fuel line.

2. I believe the felt or rubber packing gives the fuel line some flexibility. If you are using rigid connections at the sediment bulb and the carburetor, I would think the rubber fuel line would help. Use 2 pipe clamps at each end, and replace it every couple of years.

If I am wrong, please advise me.

[Dan McEachern]

You can always cut the 1/2-18 spud off of the outlet and tap the hole for a pipe thread and then use a pipe thread to tube flare adapter.

[Kevin Pharis]

There is more to a thread profile than simply pitch. Witworth threads are 55 degree, UN threads are 60 degree. You may also be surprised at the size of 1 Whitworth, approximately 1-5/8”

I am impressed at the amount of effort that the OP went thru to find an off the shelf tap in this size, but sometimes tools simply need to be custom made. Most any lathe will cut just about any thread pitch, regardless of diameter, and so a little effort can save the cost of custom tooling. Many folks fear cutting internal threads on a lathe, with a little practice they are just as easy as external threads. You can always try running the spindle in reverse so that you are not threading to a blind stop

[FireDan]

https://www.victornet.com/flypage.html

Try here. Dan
4AA045BF-2EA3-46C4-885F-A3EC90E8F8FE.png

I did order one Dan... thanks !

[FireDan]

You've made a bunch of declarations and followed up basically with "don't question me on this", so there really is no point in offering any suggestions from experience. Instead, I'll offer 2 statements and a question:

S1: 1/2-18 is the thread used universally for liquid fuel lines on cars of the period, along with flared fittings on carbs for larger cars. As for modern applications for that particular thread, I have never seen one, but that doesn't mean they don't exist.

S2: If you use a 5/16 line, you are still trying to dribble it past a too-small hole in the float valve (assuming you are using an NH)...you could hook up a fire hose to it and not get more fuel than can be delivered by a correct 1/4" line. One small constriction will undo any manner of changes performed elsewhere short of increasing delivery pressure (and that is not necessary). There is a solution to that restriction, but that is not what is being asked in this thread so there is no point in going there.

Q1: Do rubber hoses and plastic fittings belong anywhere on a gravity feed fuel system?

Now, for the benefit of anyone who is interested in these things, below is a reproduction of a factory adapter to adapt a Model T to an accessory carb Zenith S4BF...where both 1/2-18 as well as flared fittings are involved:

S4BF fuel line adapter - 37 degree flare.png

That's good Scott ....and useful. But my intent was not to argue any benefits or drawbacks ... we all have opinions . And yes , you are correct , my hope here was and is to overcome ANY fuel loss or starvation WHILE using an inline filter of the minimal type as used in gravity feed systems like tractors, motorcycles, etc. Basically this is an experiment. I may be right , I may be wrong. but easy enough to take an inline fuel filter out and replace it with a piece of rubber fuel line.

One thing there is no argument for , fire in a Model T is ugly , dangerous and destructive......

IN regards to do rubber hose and plastic belong anywhere ? The answer would be yes, many cars and vehicles have had rubber hose and plastic in gravity feed systems.

[FireDan]

1. What type of carburetor are you using? Does it need a larger fuel line for that carb? Stromberg OF does fine with Henry's fuel line.

2. I believe the felt or rubber packing gives the fuel line some flexibility. If you are using rigid connections at the sediment bulb and the carburetor, I would think the rubber fuel line would help. Use 2 pipe clamps at each end, and replace it every couple of years.

If I am wrong, please advise me.

That is sound advice DHort ! Rubber fuel line can be had that is for Fuel injection systems relatively cheap , and also is stainless steel braided, though that might be over kill. Also, the stainless coil that is on newer cars can be purchased cheap on that auction site . I bought 10 feet of 5/16 to run the steel or stainless fuel line through to protect from any vibration for $16.

[FireDan]

You can always cut the 1/2-18 spud off of the outlet and tap the hole for a pipe thread and then use a pipe thread to tube flare adapter.

That would probably work Dan , but I would like to leave the Bulb as is . That is why will make the adapter...easy enough to do .
Appreciate the input.

[FireDan]

There is more to a thread profile than simply pitch. Witworth threads are 55 degree, UN threads are 60 degree. You may also be surprised at the size of 1 Whitworth, approximately 1-5/8”

I am impressed at the amount of effort that the OP went thru to find an off the shelf tap in this size, but sometimes tools simply need to be custom made. Most any lathe will cut just about any thread pitch, regardless of diameter, and so a little effort can save the cost of custom tooling. Many folks fear cutting internal threads on a lathe, with a little practice they are just as easy as external threads. You can always try running the spindle in reverse so that you are not threading to a blind stop

That one is beyond my scope of training or budget , but yes, if one were a machinist and had the time , money, tooling and knowledge , that would be a good solution. At one time my 87 year old Dad could have done it, buy age has caught up to him . Sadly , as folks get older and die off, we have lost great resources .

[TXGOAT2]

Concerning an inline filter: Most old tractors and motorcyles had the fuel tank located directly over and well above the carburetor with a short fuel line. Most tractor filters were a bowl and screen type, designed for use on a gravity system, not a paper filter for general use on pumped systems. If your speedster has a clean tank, the original type filter is entirely adequate and capable of trapping a good deal of dirt and water without clogging. If you are using a hand pump or some type of fuel pump, a modern type filter would be OK. Most modern filters are for use on fuel injected, pumped systems. They have very high filtration, and very little tolerance for any significant amount of water or the kind of debris found in most older fuel systems. As for rubber fuel line, I've had a number of issues with it failing, both on automobiles and on lawn mower type engines. I suspect that modern fuel blends are very hard on rubber-type fuel line not specifically designed for them.

[Art M]

The fire from a rubber hose concerns me. If just plain rubber hose, i understand the deterioration. The modern rubber hose used with fuel injection should work without a problem.

Art Mirtes

[Wayne Sheldon]

I am sorry. I am afraid all I can do is frustrate you some more! However, maybe it can trigger a thought in someone that knows something I don't?
When I was making the fuel lines for my 1915 runabout (about a year ago), after buying a new gasoline tank, restoring an old brass fuel "potato", and having the era carburetor "restored" and digging out all the original fittings I had and wanted to use? I still needed those two special thread fittings. Being on a tight budget and having boxes and buckets of plumbing materials and hardware, I dug through all the small stuff I could find. I had already eliminated the cans full of original era stuff which did have a couple really odd/special pieces I could have made work, but I didn't want to destroy them for whatever era thing for which they might actually be needed.
Between my own hoarder tendencies, and my dad's true hoarder status, I had a few boxes and buckets of all sorts of odd, stupid, junk, in the small plumbing and brass fitting lines of stuff.
In there, I found TWO odd fittings, that the internal thread on one end was a perfect fit onto both the "potato's" threads and the original elbow fitting to go into the carburetor. The other end had something different (a type of flare fitting), and was connected to short ends of what appeared to be aluminum tubing. A simple modification using a hack saw and the drill press made them work perfectly to connect my fuel line.
Something out there does exist. I don't know what it is, and don't think at this point I could find the removed ends that I cut off.
Pure speculation on my part. A few things they were in a box with had me thinking they MIGHT have had something to do with automotive air conditioning????

Good luck! And don't go crazy over this.

Another thought? Years ago, I couldn't find a proper fitting, and wanted to use a larger fuel line on a speedster. I found that a small (3/8 pipe maybe?) coupler fitting would thread onto the "potato's" threads with some minor difficulty due to close but not proper threads. Thread count was close, but not right, and of course taper versus straight threads. However, some good sealant and it made a solid and reliable adapter to standard available brass fittings.
Not the smartest thing I ever did? And today I wouldn't trust the sealant with modern gasoline. However, you should be able to get a pipe fitting coupler in brass for that size! That, threaded on not too tight, and then soldered should make a solid and reliable adapter. Again, not the best suggestion. But not the worst either.

[Scott_Conger]

...for $1.75 plus shipping for a pack nut, I'd be inclined to do it right, but then again, that would leave one less thing for the next guy to do over, and where's the fun in that?

[FireDan]

Concerning an inline filter: Most old tractors and motorcyles had the fuel tank located directly over and well above the carburetor with a short fuel line. Most tractor filters were a bowl and screen type, designed for use on a gravity system, not a paper filter for general use on pumped systems. If your speedster has a clean tank, the original type filter is entirely adequate and capable of trapping a good deal of dirt and water without clogging. If you are using a hand pump or some type of fuel pump, a modern type filter would be OK. Most modern filters are for use on fuel injected, pumped systems. They have very high filtration, and very little tolerance for any significant amount of water or the kind of debris found in most older fuel systems. As for rubber fuel line, I've had a number of issues with it failing, both on automobiles and on lawn mower type engines. I suspect that modern fuel blends are very hard on rubber-type fuel line not specifically designed for them.

Appreciate the input . I think ( again, not certain) those filters I posted are meant for a gravity system . Maybe not . It's kind of an experiment . I can always take it out . I have high pressure fuel injection type rubber fuel line. Definitely no problem using that in a gravity system .

[FireDan]

I am sorry. I am afraid all I can do is frustrate you some more! However, maybe it can trigger a thought in someone that knows something I don't?
When I was making the fuel lines for my 1915 runabout (about a year ago), after buying a new gasoline tank, restoring an old brass fuel "potato", and having the era carburetor "restored" and digging out all the original fittings I had and wanted to use? I still needed those two special thread fittings. Being on a tight budget and having boxes and buckets of plumbing materials and hardware, I dug through all the small stuff I could find. I had already eliminated the cans full of original era stuff which did have a couple really odd/special pieces I could have made work, but I didn't want to destroy them for whatever era thing for which they might actually be needed.
Between my own hoarder tendencies, and my dad's true hoarder status, I had a few boxes and buckets of all sorts of odd, stupid, junk, in the small plumbing and brass fitting lines of stuff.
In there, I found TWO odd fittings, that the internal thread on one end was a perfect fit onto both the "potato's" threads and the original elbow fitting to go into the carburetor. The other end had something different (a type of flare fitting), and was connected to short ends of what appeared to be aluminum tubing. A simple modification using a hack saw and the drill press made them work perfectly to connect my fuel line.
Something out there does exist. I don't know what it is, and don't think at this point I could find the removed ends that I cut off.
Pure speculation on my part. A few things they were in a box with had me thinking they MIGHT have had something to do with automotive air conditioning????

Good luck! And don't go crazy over this.

Another thought? Years ago, I couldn't find a proper fitting, and wanted to use a larger fuel line on a speedster. I found that a small (3/8 pipe maybe?) coupler fitting would thread onto the "potato's" threads with some minor difficulty due to close but not proper threads. Thread count was close, but not right, and of course taper versus straight threads. However, some good sealant and it made a solid and reliable adapter to standard available brass fittings.
Not the smartest thing I ever did? And today I wouldn't trust the sealant with modern gasoline. However, you should be able to get a pipe fitting coupler in brass for that size! That, threaded on not too tight, and then soldered should make a solid and reliable adapter. Again, not the best suggestion. But not the worst either.

Good stuff Wayne! And yes, my dad said " go out and look through my fittings..... that is a whole drawer on an old navy battle ship machinist cabinet ! He is 87 .... and had I had that potato in my hand , I might have done it ! I may yet ! I get the feeling from some folks here that if it isn't original it is sacrilege....But this is a Speedster , it will never be original ....it certainly wasn't the way I bought it and the way it was built 40 years ago in Oregon.... and I can say , without a doubt , it is far better now than when I got it ...no plexiglass windshield , real safety glass ! Speaking of not original, I am out the door to get my last 2 rims and an extra from the powder coater , and two green ones for the camp trailer !!! Ca-ching $$$$...

[TXGOAT2]

A screen and bowl type filter will usually give the best results on a gravity-fed, carburetor system with a vented fuel tank. Regardless of any filter type used, a reaonabley clean fuel tank is a must.

A dirty tank will quickly clog most modern throwaway paper filters, and will require frequent filter service on the earlier, bowl and screen type filters. A functional fuel shut off valve is a good thing to have on any gravity fed fuel system. A Model T and other early cars with a gravity system and updraft carburetor are capable of draining an entire tank full of gasoline onto a garage floor if the float valve should leak, or if the float istelf develops a leak and no fuel shut off is present, or not used, or itself leaking. I would never park an early car with a vented carburetor and fuel tank in any enclosed space with an ignition source, such as a hot water heater or other heating device that had a pilot light or spark igniter. Any car, lawn mower, ATV, etc ought to be stored in a well ventilated space with absolutely no source of ignition present.

[FireDan]

A screen and bowl type filter will usually give the best results on a gravity-fed, carburetor system with a vented fuel tank. Regardless of any filter type used, a reaonabley clean fuel tank is a must.

A dirty tank will quickly clog most modern throwaway paper filters, and will require frequent filter service on the earlier, bowl and screen type filters. A functional fuel shut off valve is a good thing to have on any gravity fed fuel system. A Model T and other early cars with a gravity system and updraft carburetor are capable of draining an entire tank full of gasoline onto a garage floor if the float valve should leak, or if the float istelf develops a leak and no fuel shut off is present, or not used, or itself leaking. I would never park an early car with a vented carburetor and fuel tank in any enclosed space with an ignition source, such as a hot water heater or other heating device that had a pilot light or spark igniter. Any car, lawn mower, ATV, etc ought to be stored in a well ventilated space with absolutely no source of ignition present.

.
That is truly sound advice about the shut off and parking with an ignition source. 20 years or more ago , there was a Central Fire fire Captain here who was cleaning a motorcycle tank in front of his garage, outside, with a gas water heater in the back corner of an attached garage. The vapors carried back into the garage , it flashed , and the short version is , he died because of it . Fuel is very dangerous ! I have witnessed while camping at Big Basin , someone throw white gas on a campfire in the next camp site : It went through the fire , hit the tent behind , and POOF in 3 seconds that tent was fully ablaze on the ground , and it was a huge tent . Thank god no one was in it .

[TXGOAT2]

Gasoline vapor is highly flammable, if not outright explosive, and it is heavier than air. Absent air currents, it can do some remarkable things.