Technical Inline Fuel Pressure Gauge

Simple device, simple installation right? Not for me, can swap out an engine, but this kind of thing always kicks my ass.

First thing, have pretty much eliminated rubber fuel hose from the equation for safety reasons, it's solid steel fuel line from pump to carb inlet. When I look up inline fuel gauges though, every one has those barbed fittings for rubber hose and hose clamps. Also when I look in the catalogs for fittings and connectors they have 50 gazillion different fittings, and my eyes start to glaze over.

I'm just a simple guy trying to do a simple job, want a pressure gauge that will screw into the fuel inlet of the carb, and the fuel line into the other end. Is that unobtanium?

 

Dickster here on the HAMB sells a nice low pressure gauge that you could easily tee into your hard line, but most likely will not screw directly into your carb:
https://www.jalopyjournal.com/forum...ic-fuel-pressure-gauge.1036051/#post-12179570

 

Hm, that might work. You're still gonna have to talk to me like I'm 5 though to install it. Otherwise I'll order the wrong parts.

I guess whatever gauge I end up with, could be installed at the fuel pump outlet or, at the carb inlet? Line itself is actually brake line I bent up, into a brass Autolite 2100 carb fitting.

 

Well get a tee that is inverted flare that fits your tubing on two ends and 1/8" pipe thread on the other side for the gauge and splice it into your line:

 

Are you sure you don't want to incorporate some rubber fuel line into the run from the pump to the carb to absorb vibration?

 

The OEM did not, was my thinking. They have two (short) separate rubber fuel lines, one under the cab and another between the frame and the fuel pump.

 

OEM did not think a gauge was necessary, either. Why not just say "Personal preference" instead of blaming OEM?

Ben

 

Vibration between pump and carb is in sync since they are both mounted solidly to the same engine. Just mount everything solid with good supports and no rubber hose is needed. Between the car body or frame and the engine is a different story, rubber line is required there.

 

I'll just add that the gague Dickster sells is a low pressure 5 PSI gauge and I used it as an example of a small gauge that would splice in easily. Your fuel is most likely a 5-7 PSI so a 10 or 15 PSI max gauge would work. Lots of choices. So a gauge, a tee, and two flare nuts and you are done. I'm assuming you have a double flare tool, or have a buddy with one.

 

Put a T in your fuel line and buy a screw in gauge. The screw in gauges are easy to find and they work.

 

Remember when I said ya gotta explain stuff like I'm 5 ? LOL These all look like barbed T fittings for rubber hoses. This is why I hate shit like this. Nothing is ever simple anymore.

 

You are looking at the wrong kind, as jmountainjr pictured here is what you need.

Pat

 

Well, pay attention or pay the price

Ben

 

I assume you used 3/8" tubing? If so, the flare nut threads are 5/8"-18. You are looking for a female inverted flare branch tee. The threads on each end will be the 5/8"-18 for the flare nuts that fit your 3/8" tubing. The side port on that size fitting is usually 1/4" tapered pipe thread. Parker, Dorman, etc. all make them and will come up on a Google search if you prefer that to going to a parts or hardware store. And also get two flare nuts to put on the ends of the tubing where you cut your splice. Once you have the tee fitting, just get a gauge with the same size pipe thread if you can. If not you'll most likely need a bushing down 1/8" pipe if that is what your gauge has for threads. The whole job won't take longer that a beer, or two.

 

Just remember there are about 10 “Different” types of fittings out there, flare, inverted flare, Farrell, jic, 45 degree, pipe, swedge, o ring etc and for the most part they don’t interchange. First determine what you have, second determine what you want, the buy an “Adapter” to change from one to the other. Yes I know most “fittings” are adapters. If you look long enough, yo may be able to find a street pipe tee with a inverted flare for the gas line, could get the job done with one fitting/adapter. Simple. Bones

 

64, also don’t be scared of some neoprene in your gas line. I know here on the forum it’s got a bum rap recently. But neoprene gas line properly installed and changed periodically, is still a good gas line in my opinion. Ford used it for years on their carburetors. A gas line that is solidly mounted on both ends can set up a vibration and cause a crack. I’ve been using neoprene gas lines for pushing fifty years with no problems. Bones

 

Get this: https://www.holley.com/products/acc...es/gauge_adapters_and_fittings/parts/16775NOS

and this: https://www.holley.com/products/fue..._gauges/gauges_and_components/parts/100189ERL

Screw the T fitting into your carb, then the gauge into the T, then your NPT to inverted flare fitting will screw into the other side of the T.

 

If you want to mount it into a hard line on your engine, do the brass tee with inverted flare on the run ends and a female pipe on the branch. You can get a low pressure gauge, usually with a male 1/8” male pipe thread you can screw into it. As far as vibration, you can also get a liquid filled gauge. These are made to absorb the vibrations such as being on an engine.


Sent from my iPhone using H.A.M.B.

 

I knew it was out there. Thanks for your help.

 

Did have some older hose split on me in the garage once and was surprised at how far and wide fuel can spray even at just a few psi, kinda made a believer out of me.

Looking at the the factory set up in photos and manuals there was no rubber line at all after the pump. Though you guys aren't talkin' for the hell of it either - could see flex cracks developing over time - maybe this is why any complete originals are always long gone, seem to have been cut at some point, and have hose sections 60 years later. Hm.

 

You are running a hard line, you just buy a T that is a flare fitting or a T that is for an AN fitting.

here is an An to pipe they also come with a female pipe instead of male if you don't want to use a coupling.


Or here it a flare to pipe fitting



or here is an inverted flare to pipe


An inverted flare to pipe would use a nut like on a brake line.

I do not know what size fuel line you are using, but most fuel pressure gauges are 1/8" NPT (national pipe thread) so you size your T appropriately. For instance if you are using 5/16 fuel line you would want a T that was 5/16 flare to 1/8 NPT.

 

Yeah, it's starting to make sense. What I didn't quite get was NPT fitting size is designated by the ID, not thread diameter unlike everything else. So someone would mention a 1/8" fitting and it didn't sound right.

But I thought the actual seal at the business end of the fuel line was done by the flare end of the line crushed against the brass fitting, just like brake line? The T fittings don't have that, or not needed??

 

This would fit inline with what I have right now correct? No cutting, flare tools, or jiggery-pokery required right? Permatex thread sealant, a decent gauge, and Bob's yer Uncle? $12 de-livered.

 

This would fit inline with what I have right now correct?
Is the Autolite adaptor fitting you have screwed into your carb now 1/8" pipe thread on the carb end? Not all carb inlets are pipe thread. At least some Autolite 2100 are not pipe thread. Many look to be 1/2"-20 straight thread. But if in your case it is 1/8" pipe, then that one would work. If the carb inlet is 1/4" pipe, then you would need the same fitting in 1/4" and then likely need to bush one side down to 1/8" pipe for the gauge. A 1/8" male pipe thread OD is just a bit bigger than 3/8" and the OD of a male 1/4" thread is just a bit bigger than 1/2". 1/8" pipe threads are 27 TPI and 1/4" pipe threads are 18 TPI.

 

64, in your pic, it looks to be the 1/2 inch straight thread. I looked closer at your pic and I think I can see the compression gasket. There for the fitting in the pic won’t work. You will have to use the tee with two inverted flares and one pipe thread and some short inverted flare lines. If you had the carb with pipe fittings, your street tee would be the ticket. Bones

 

That is what I am seeing also Bones.
He would need to cut his hard line and make up another line so he could install the T fitting.

 

Here is a 1/2-20 straight thread to 1/8 npt adapter: https://quadrajetparts.com/pipe-thread-inlet-fitting-p-1412.html

Using some calipers you should be able to tell if its 1/8 NPT or 1/2-20. NPT should measure about .405" OD (across the threads at its largest) and 1/2-20 should measure about .5".

 

That part in the picture looks like a female flare fitting but that is not what the caption says.

 

I noticed that as well, however I find it less likely they miss typed the description twice then used the wrong picture - if I were to buy it I would probably give them a call before ordering just to confirm.

 

The fuel line is just the steel double flare brake line in different lengths that NAPA sells on their racks. It takes a 1/2" wrench on the flats, the brass fitting on the 1963 2100 carburetor takes an 11/16" wrench, and has the SAE flare seat.

Looking at the idea again it may run into clearance issues with the gauge itself and the oil bath air filter body, not sure on that.