Thread: Fuel vent

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According to Magnafuel's website, their lowest pressure carburetor pump is 18#, and requires a return line?
QuickStar 275 |MagnaFuel

I personally don't like the liquid filled gauges but could care less what others want to use---a pressure guage will read the pressure in the line and will only be effected by the outside atmospheric pressure------- the dips/swings of a gauges needle is a result of the IMPULSES in pressure-maybe effected by pump and/or regulater action. The larger Holley type carbs have larger diameter needle/seat assemblies and so are more sensitive to line pressure leaking past-

The fuel system with a BIG pump and a return line circulates the fuel in and out of the tank causing under vehicle heat to warm up the entire load to whatever temp the under side of car is seeing.

In this guys case he could shut off electric pump and run car til it quits--------also check tank temp after a road trip to see what the fluid temp rises-

How do I insert pictures

Originally Posted by Ken1960

How do I insert pictures

open a post ... look for " Go Advanced "on the right side of your screen ...click on that ...scroll down a bit and you will see " attachments " .. next to that you will see . " manage attachments " open that and you will see " add files " at the top right of the page ...click on that and you will see " select files " .. click on that and your pictures will pop up .. click in any picture you wish to add and hit " open " .. man !! i dint realise how hard it is to add a picture here .. i may have left out a dozen or so steps ...

When I hit inline trying to upload pictures they won't do nothing trying to import pictures

Well it did work

I have tried to load pictures but got one so far , but my motor just makes 7 1/2 vacuum and got a 950 qf An I had a 4.5 power vale in there holly says I need a 3.5 in there ,would that help on being so rich and would a 3.5 be enough what would changing them out do to it

The vacume numbers divided by 2 is a good guide line for the power valve--------But--with all you issues, you need to be sure that possibly a back fire pop or two hasn't blown out the diaphragm in the PV.

If your into your carb, check your floats-if they are brass make sure that they aren't leaking and partally filled with fuel which will make them JUNK-if they are the nitol plastic type ones they are probably ok-check that they aren't rubbing on anything because they are bent, etc------If your carb has any of those jet extender tubes make sure the bottom of the floats have the clearance notches for them.

From your pic----I think where you have the regulator mounted makes the lines to the float housing bent/twisted too much and may restrict fuel at higher flow ( of course now we are trying to slow fuel down) No matter what type of guage you have it will show the pressure that is there relative to outside atmospheric pressure irregarlis to whether the guage is liguid filled or not-------I DO NOT recommend liguid filled gauges for any application. People seem to want them to dampen fluation of the needle but the needle movement is because of the pressure it is seeing.

Also-I see that your feed line up to the engine is laying on the head?????? nice way to warm the fuel up to 240*--------I'm thinking you probably should start reconsidering your complete fuel system routing and configuration

Very good points, but liquid filled gauges have a purpose. I don't believe that liquid filled is necessary on an auto fuel pressure, but I'd still buy one because of their benefits. This is from the sales literature, guidance for proper selection of pressure gauges:

SO, WHAT ABOUT LIQUID-FILLED PRESSURE GAUGES? DO THEY PERFORM DIFFERENTLY?

Yes, they do.Liquid Filled Pressure Gauge

If dry gauges are work horses, then liquid-filled pressure gauges are like the Budweiser Clydesdales, doing the same job but with greater precision and yeah, I’ll say it...style.

Liquid-filled pressure gauges are available in pressure ranges equal to or higher than their dry counterparts.

Their casings are filled with fluid, usually glycerine, although silicone or other liquids are sometimes used. The liquid coats the internal parts and is visible on the gauge’s face.

Having the liquid inside works to dampen the effect of pulsation and pressure spikes - which is another advantage over choosing a dry gauge.

This means the pressure gauges are less likely to give inaccurate readings due to wear and tear that mechanical vibration and pulsation tends to cause.

The liquid in these pressure gauges does double duty when it comes to fighting those effects. Not only does it help mitigate the effect of vibration, the liquid also lubricates the gauge’s moving parts, reducing everyday friction.

The filling also has the benefit of preventing internal corrosion. As the bourdon tube and movement are covered by a liquid that keeps moisture and other corrosive substances at bay.

All of those factors add up to longer service life and lower replacement costs for liquid-filled pressure gauges over dry pressure gauges. And in environments where vibration and condensation are a factor, they are definitely a consideration.

Roger-The only thing the liquid filling does is to dampen the fluatuation of the needle because of the immersion of the needle in the fluid-the lubing of the moving parts of the guage is highly questionable as an asset because more of these gauges are replaced because of leakage of the fluid than other dry gauges are because of worn out needles.

If you guage needle is fluactuating its because your pressure is also--------fix the cause and the needle wobble will go away.

Originally Posted by Ken1960

holly says I need a 3.5 in there ,would that help on being so rich

Is this a new symptom? Is your motor rich now, or are you referring it to the cause of the gas smell in your garage?

IMHO, the power valve's vacuum rating only relates to when the valve opens and would not cause a gas smell. Also, unless the valve's diaphragm is ruptured, the higher vacuum valve should not cause a rich mixture condition, but rather a momentary lean condition under power. The lower value valve will help eliminate a stumble under hard acceleration.

Jerry, the liquid fill surrounds the entire internal mechanism of the gauge, and the viscous fluid damps the vibration of the bourdon tube, the linkage from the bourdon tube to the needle and the needle itself. As Denny points out, another approach when one is dealing with a pulsating pressure is a pulsation dampner. Often, in severe services like a fluid pump discharge pressure the answer is both, a pulsation dampner to chop the highs & lows, and liquid fill to dampen the result. It is not a question of "fixing" the pulsation. The pulsation in a fluid pressure is there because of the process, not something wrong to be "fixed". With that, I'm done.

Isn't it sort of hard to set the correct pressure if the gauge is pulsating? Then you just are averaging the distance the needle travels and cutting it in half and calling it good. We have several liquid filled gauges on equipment at work. I'd only use a non liquid filled one if it were the last one I had. The only failure I've seen with these gauges are from vibration from the equipment cracking the bordon tube. And these aren't cheap gauges. The pressure settings are pretty critical to the equipment's operation, and I can't see a non liquid filled gauge being ideal. Just my .02.

Meanwhile, back to our regularly scheduled program.

It just dawn on me, I have two hot rods in my garage both carbureted and vented tanks, seldom do I smell gas, occasionally a small wiff. If you have enough gas fumes to stink up your garage and house, you have a leak.

It is well known that the fluid in the gauge (glycerin) swells with heat and the reading will become lower the hotter the fluid becomes.

That's why his readings at home were higher, then he drives to town and the readings fall. No big deal as long as he's comparing these readings , say at each startup, when the motors is cool / cold.