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Can Boiling Point of Gas Be Raised?


Steve_Mack_CT

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Take a look at the article below. Interesting that the writer suggests certain additives can raise boiling point of gas in the first section. This is another vexing problem with Ethanol mix, which is about all you can get here in CT.

I have largely eliminated this problem with all fuel system components rebuilt, and an electric fuel pump but will get occasional stumble with a hot (after say, an hour run) engine idling or in traffic if it is say, 80 or hotter out. I suspect as the article suggests even with all these steps you can still get the crap gas to boil if it is hot enough under the hood.

Any thoughts on this? What if any additives would do this and why? I have heard true lead (LeadMax2000 or simillar) may do this as well?

Can anyone speak to the validity of this or is anyone currently using an additive for this?

Troubleshooting Carburetor Problems and Vaporlock Blues Revisited - Hagerty Lifestyle

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Add some heavy ends. Kerosene diesel fuel or stove oil will work. These will raise the boiling point of the fuel but reduce the octane. Lower octane will not hurt your car if the compression is low. Generally speaking if your car was made before 1953 it has low compression. Prewar cars have very low compression and will run better on gas that has some kerosene added. Depending what your compression is you could add 5% kerosene up to 25% for cars from the 20s with very low compression, like 5:1 or less.

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Steve, gasoline isn't a single chemical compound but a mixture of hundreds of individual chemical compounds which have a large range of boiling points. Adding some additives can raise the AVERGE boiling point but cannot remove the lower-boiling components, so regardless of what higher ends are present, the initial boiling point will remain that of the most volatile components. That's not to say that adding something like kersene won't help, but it can't eliminate the volatile components.

Some cars are much more apparent to vapor locking than others, I"ve never experienced here in NJ with either of my older Packards which see all kind of hot summer driving conditions.

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Changing the vapor pressure (and thus the boiling point) of gasoline is not new. Refineries have been doing this for decades. Typically there are "winter" and "summer" blends with different vapor pressures to promote atomization at cold temps and to discourage vapor lock at hot temps. One common problem is when you have an abnormally warm day in the winter, and the low vapor pressure gasoline in the car will vapor lock on that hot day.

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Guest Bob Call

I remember when I was a teen in the 50's and everyone had a flathead Ford V8 or a Chevy stovebolt 6. Vapor lock was just a fact of life for the Fords. The fuel pump and fuel line setting top center of the engine was not only in the hottest ambient temp, except for the exhaust manifolds, under the hood they acted as a heat sink transferring heat from the block to the air. All kinds of remedies were tried. Spring clothes pins, aluminium foil, wet burlap, etc. wrapped around the fuel lines. None of them worked. Just open the hood and let things cool. The reliable, albiet slower, stovebolts never suffered vapor lock because the fuel pump and lines were up front in the airstream of the engine fan. Rich boys replaced their 216 stovebolt 6's with GMC 270 or 302 sixes with a performance "full race" cam.

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I found this document on my local Oil Refinery's web site and it may help explain some of the problems with vapor lock and hard start.

http://www.frontieroil.com/attachments/contentmanagers/106/PrdctsSpec_UnleadGasSpecs.pdf

In this document is a chart for Seasonal Gasoline Specifications. Gasoline vaporizes according to fuel system pressure.

December - February gas mixture begins to vaporize at 11-15psi at 105 deg F

April gasoline is 9-11.5 psi at 124 deg F

and May gasoline is 7-9 psi at 140 deg F

If you had winter gasoline in your Antique car on a 100 deg day you would only be about 5 degrees from vapor bubbles in the fuel. A vapor lock condition would be caused.

If you purchased April gas when you take your Antique out of winter storage it is only a month until the switch from 124 deg F to 140 deg F. This might explain a lot of problems in early summer.

I Have problems with the fuel temp in my 1937 Buick. I can start my car instantly after sitting in a cool garage at about 75 deg F. Drive 30 miles and then park for 20 minutes. As the car is parked Temperature

Will rise to above 180 degrees on the Temperature gauge. Much of the excess engine heat will end up soaking the fuel system under the hood. The fuel pressure is at 1 - 3 psig since the pump is not running.

The summer gasoline vaporizes in the line and the heat soak is quicker and longer on hot day's. If I wait a hour for the system to cool to ambient temperature then it starts easy.

I have a electric pump at the tank to try and speed up the fuel cooling process but if you have a 100 deg F day you may have fuel near 100 deg F in the tank.

If I could get 75-85 octane, non-ethanol, Regular gasoline that vaporized at above 180 deg F, I think my car would run fine all the time.

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Steve, gasoline isn't a single chemical compound but a mixture of hundreds of individual chemical compounds which have a large range of boiling points. Adding some additives can raise the AVERGE boiling point but cannot remove the lower-boiling components, so regardless of what higher ends are present, the initial boiling point will remain that of the most volatile components. That's not to say that adding something like kersene won't help, but it can't eliminate the volatile components.

Some cars are much more apparent to vapor locking than others, I"ve never experienced here in NJ with either of my older Packards which see all kind of hot summer driving conditions.

Interesting theory. If this is true, how come adding antifreeze to water raises the boiling point? Wouldn't the water still evaporate at the same temp?

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Great feedback from a knowledgeable group, guys! I appreciate it. couple more questions, Rusty, what exactly are "heavy ends"? Also, what is it about Kerosine, and possibly the products like LeadMx or Marvel Mystery Oil (mentioned specifically in the article) that drive some improvement?

I feel I am 95% there, and a slight improvement would be all I need - for now, that is unless the ethanal mix changes (your tax dollars at work...). I will be trying one of these but am curious what is the active ingredient(s). Thinking Kerosene is probably the way I will go at this point. Never tried it with my old Model A Ford but I heard that they will actually run on Kerosene..

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The term heavy ends may be old fashioned and obsolete. A long time ago it was in use in the oil business.

In refining crude oil they distill it to separate out the different products. The thinner, lighter products are at the light end of the scale the thicker heavier products are at heavy end. You could arrange them on a scale from naptha gas, gasoline, kerosene, stove oil, diesel fuel, light lubricating oil, heavy lubricating oil, grease, asphalt.

Gasoline at the pump is a blend of different chemicals. Octane is an actual chemical which would be at the light end of the scale for gas, kerosene would be at the heavy end.

There is no hard and fast cutoff for any of these. In the early days of the oil business the demand was for kerosene or coal oil. They put everything they could into the coal oil including what we would consider low grade gasoline. In those days before 1905 kerosene had a strong piercing odor and coal oil lamps sometimes exploded. Gasoline was so light if you left the cap off a gallon can it would all evaporate in a few days.

By 1913 it was the other way around. They sold more gas than coal oil. So they started putting more of the low grade gas, or high grade kerosene into the gas. It was about this time that car makers lowered the compression ratios, went to long stroke motors, and developed hot spots and vaporizers on their intakes to burn the new low grade or low octane gas.

This went on until they developed the cracking process which allowed more flexibility in what they got out of the crude. From that time on octane ratings slowly rose, helped by the addition of more and more tetraethyl lead.

The peak was reached in the sixties when heavily leaded gas of over 100 octane was available.

Starting in 1970 leaded gas was taken off the market resulting in the gas we have today.

Today's cars are all fuel injection so it doesn't matter how easily the gas evaporates, it is under pressure in a closed system from the tank to the intake.

I'm suggesting to raise the boiling point by adding heavier or oilier substances such as kerosene.

Yes the light elements will still be in there. But the heavier elements will raise the boiling point of the mixture.

Edited by Rusty_OToole (see edit history)
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Rusty, if you can find a cooperative local high school chemistry class, take a small amount of gasoline, split it into 2 portions, add 5% or so kerosene to one half, and have them do a fractional distillation on both. You'll find they both have the same initial boiling point - been there and done it.

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  • 2 years later...
Guest bobburns

Owen_Dyneto:

I realize this is an old post - but when people write things that are WRONG - it leaves the next Joe who comes along thinking that is the correct answer when especially in this case - it is NOT.

What you write in post 12 is NOT correct. The chemistry class experiment you are referring to will yield the approximate boiling (vapor) point at STP - Standard Temperature and Pressure ONLY. The two will be very close to the same just as would Water and Anti-Freeze boiled in an open pot.

What Rusty writes IS correct. Adding heavier weight hydrocarbons WILL raise the vapor point under pressure - usually enough to keep the fuel from vaporizing in the line or boiling off in the carburetor bowl while flowing.

Volatility is a measure of the gasoline’s tendency to vaporize under a given set of conditions. Reid Vapor Pressure (RVP) is a commonly used indicator of gasoline volatility. Boiling is a violent version of vaporizing. The higher the RVP, the greater the tendency to vaporize or vapor lock.

Among other places on the web - you will find a fairly good dissertation of the issue at => Evergreen Performance Systems, Inc. and Hydrogen Power Central | The true source for powering engines with Hydrogen - not "HHO"

I mix Industrial Maintenance Coating Thinner (IMCT) around 1 oz per gallon - which is basically a blend of petroleum distillate in the paint thinner / mineral spirits (once called also "white gas") family and ethyl acetate and not only does it cure vapor lock it increases octane because you can feel it in the power and acceleration. When it burns however, it is an eye and throat irritant, even though it raises octane, burns hotter, easier, and cleaner.

Google ethyl acetate and pay attention to it's "pure" boiling point, and remember IMCT is a blend of a white gas family of a petroleum distillate and ethyl acetate. "Pure" Ethyl Acetate could be called an "alcohol" as Ethyl acetate is the ester of ethanol and acetic acid; and it is manufactured on a large scale for use as a solvent.

What we call gasoline - as Rusty showed; is blended today - and the various chemicals blended into it for the various regions and state laws make it a special product where you BUY it. It is not all the same.

One must understand the chemical reactions and interactions of blending other hydrocarbons into what we call gasoline and then still have it able to have the same properties desired of the product called gasoline.

Putting kerosene into gasoline - while both are hydrocarbons - and they will blend - the lighter oil nature of the kerosene to the solvent of gasoline; in an amount of 5% is not enough to change the STP vapor point of the gasoline, but it will weaken the octane rating of the gasoline enough to feel it under acceleration AND under pressure will raise the vapor point enough to perhaps prevent vapor lock depending on the ambient and under hood temperatures of where one is located.

So - you cannot just say whether it will work or not

But, . . . YES the boiling point of gasoline can be raised (or lowered) by an additive - depending on what it is - as can the autoignition temperature which will increase "knock" - using the right additive for the fuel you just bought and put in your tank is the trick and it is always going to be hit and miss - depending on what refinery produced the gasoline in the first place.

One needs to have studied Chemistry as I have to actually know how this works

Bob

Rusty, if you can find a cooperative local high school chemistry class, take a small amount of gasoline, split it into 2 portions, add 5% or so kerosene to one half, and have them do a fractional distillation on both. You'll find they both have the same initial boiling point - been there and done it.
Edited by bobburns (see edit history)
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Bob,

I am having problems understanding why you say OD is wrong and Rusty is correct, it seems to me you are all saying much the same and that is that gasoline is made up of many components each having different boiling points and the components with the lowest boiling point are the cause of vapour lock.

I have used kerosene to avoid vapor lock and there is no doubt it helps, the more the better up to 20% in a low compression 1920's car. It makes no discernible difference to power but if the conditions are sufficiently adverse it will still vapour lock and then you just have to wait until it cools.

I would like to try IMCT, how is it sold? Is it a product that would be sold by a panel beater's supply shop? Is there a brand name?

In answer to Rusty's comment about adding anti freeze to water, the difference is that water is only one material, H2O, with a single boiling point (varied only by pressure).

I like the attached simple explanation of the issue.

David

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Check "Reid Vapor Pressure" in Wikipedia, or similar. It is a measure, as I understand it, of how readily the fuel will evaporate in open air. It IS variable and a result of the various fuel blend components.

I recall when Texaco used to advertise their "customized for your area" gasoline, in the earlier 1960s. Seems like the first "RFG" was closer to the old "winter" blend, which had more higher-end distillates so it'd vaporize nicely in cooler weather. Then, we got what was loosely described as winter gas, all year round, with RFG. That was in the 1990s, so you can project to more current times and suspect we have something more sophisticated now. In the fuel use map in the Exxon or Mobil gasoline websites, there are a few places where the Reid Vapor Pressure spec is varied from other fuels. In some areas, according to the map, RVP can vary from about 7.0 to 9.0 in some of the fuels.

I wanted to upload the map, but at 2.73mb, it was too big. You can do a Google search for it, though.

Just some thoughts,

NTX5467

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Guest Al Brass

On occasions here in NZ, we get extreme heat and old cars vaporlock. A quart of diesel added to the gas tank solves the problem without any more in side effects than a slight smell from the exhaust. A larger tank might need two quarts. Try it, I think you will find it works.

Regards

Al

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Bobburns thank you for the confirmation and technical explanation. I prefer to keep things simple but I appreciate the more correct technical approach.

To keep it on simple terms, several people have confirmed that adding some kerosene, diesel fuel or stove oil will reduce the tendency to vapor lock and will NOT hurt an older model, low compression engine. Some have reported more power, easier starting and cooler running especially in very low compression cars of the twenties and early 30s.

This approach is not recommended for higher compression cars made from the mid fifties onwards.

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In the later 1960s, it was somewhat common for people who were going on vacation, in the summer, to add a gallon or two of diesel to a full tank of gasoline for their trip. No mention of vapor lock issues, but engine de-carbon activities. Might have been along the same lines as adding a quart of atf to the engine oil to help quiet noisy hydraulic valve lifters, or for "sludge clean-up" activities?

Just some recollections . . .

NTX5467

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Guest bobburns

DavidMC: (re post #14)

IMCT is found in the paint isle of any hardware or home improvement store usually in quart or gallon cans.

OD says the Boiling point of gasoline cannot be raised by adding a heavier hydrocarbon - such as kerosene or diesel - and points to a high school chemistry class experiment as his proof. Rusty said any heavier hydrocarbon WILL raise the boiling point - and I said Rusty is correct and OD is wrong.

Once these chemicals are blended - the over-all resulting chemical properties - especially boiling point under pressure is changed - they are NO LONGER SEPARATE boiling points in play. Thus the "lowest boiling point are the cause of vapour lock" is also NOT CORRECT thinking.

What one is after is new "liquid" fuel which vaporizes easily in open air, lights easily and has a rapid flame spread but NOT a hot explosive one, and burns easily and completely under one atmosphere of pressure - what we call 14.7 to 1 - BUT - and this is most important; does not auto-ignite at a low temperature and WAITS to be lit by the spark after being compressed in the cylinder.

Vapor lock is caused by usually a fuel that vaporizes too easily at too low a pressure (in the line) due to under-hood heat and not enough pressure on it - which would run great if it could make it to the combustion chamber first. So the goal is to raise the vapor point temperature without lowering the auto-ignition temperature or flash point or flame spread speed - or increasing the flame spread speed too much. Easier said than done - especially without a "chemistry set"

OD says a simple high school chemistry experiment will show this - BUT I said the boiling points will appear the same under STP (Standard Temperature and Pressure - which is one atmosphere of pressure at 77 degrees F - commonly room temperature ) - BUT under pressure in a fuel line the boiling point (vapor point) will be raised enough to prevent vapor lock at higher temperatures. See Standard conditions for temperature and pressure - Wikipedia, the free encyclopedia

In fractional distillation (the refining of oil) - what we call "mineral spirits", "paint thinner", "kerosene" and "diesel fuel" all ALL "heavier" hydrocarbons (pretty much in that order) than what we call gasoline - in that they occur lower in the distillation tower and condense at lower temperatures back into liquid before what we call "gasoline" does.

Refining of oil is basically heating it into vapors and then capturing those vapors various degrees of cooling - at the top is "propane" - at the bottom is "pitch" or "road or roof tar"

Any of these heavier than gasoline petroleum distillates above will raise the vapor point of gasoline if mixed into it.

IMCT is a "new product" from Klean-Strip® they call "Industrial Maintenance Coating Thinner" that provides good solvency and can be used in place of MEK, Toluene, Xylene and VM&P Naphtha for thinning Industrial Maintenance Coatings. This product is intended only for the thinning of industrial maintenance coatings. It is not intended to be sold or used for any other purpose.

As you can see from what it replaces - it is "hot" solvent - but not quite as hot as acetone in its ability to dissolve other things

It is as said - of the "paint thinner" family in weight with ehtyl acetate blended in to make it's solvency properties a little "hotter " and stronger.

A small amount of IMCT in gasoline - depending on whether it is the winter or summer blend - depending on what that is as a fuel where you are - raises the boiling point like kerosene or diesel - but also raises or maintains the octane level slightly as ethyl acetate tends to loosen the hydrogen bonds and lets mixture burn more completely without causing pre-ignition we call "detonation" - which is really simply a slight lowering of the "autoignition temperature". When it does light - the flame spread is faster but not so fast as to "knock" or be a violent explosive hard burn of the fuel.

It does however produce an irritating fume that irritates the eyes and mucous membranes when burning in gasoline.

The BP article does not address how to re-blend your own fuel, and indeed - each batch of gasoline - and even how long it has been sitting in a tank will change it's properties as certain things evaporate out of the fuel changing it's properties if in a vented tank.

The issue is boiling points UNDER PRESSURE we are talking about here - though the BP article speaks to other issues of engine and carburetor design contributing to the vapor lock problem. Plain WATER has great cooling properties, but under pressure will boil at a lower temperature than anti-freeze mixed with water - up to a certain point. Too much anti-freeze - (typically ethylene glycol) causes the opposite effect even under pressure of the cooling system. Note also that PURE ethylene glycol is also flammable but also miscible with water. So in an open cup the boiling points would also appear the same as water but under pressure the boiling point is different. As an example water would boil and thus "vapor lock" at a really low temperature without ethylene glycol.

The BP article explains causes - not how to change fuel formulations - so for this discussion it explains nothing. BP cannot by law tell you what you can blend into fuel to change its properties - but any petroleum distillate can be used - and the ester family - many of the alcohols we call them - can also be used.

There is no "chemistry set" method to measure fuel vapor points. I can only say acetone will lower flash point (light easier) but also lower auto-ignition temperature and thus create knock into too much of a quantity - while a very little bit will raise octane but not lower auto-ignition - so if you go TOO low with kerosene or diesel you can bring back some kick to the fuel with SMALL amounts of acetone. Conversely if you go too high and it knocks - you can bring it down with kerosene or the paint thinner family.

I have found IMCT is a happy medium that does both in the right quantities - raise boiling point and octane just enough to be a "goldie-locks" kind of additive to help prevent vapor lock. If you put in too much you can return the fuel to some "kick" without knock with a small amount of acetone. The ethyl acetate in the IMCT loosens hydrogen bonds on the gasoline making it easier to light to burn, but the "oil" - heavier hydro-carbon nature keeps the vapor point higher and flash point still low enough to give good performance

None of these contain lead and so should not damage a catalytic converter if you have one, HOWEVER too much IMCT will prolong the burn and may result in unburnt - STILL burning HOT gas being exhausted in the exhaust cycle. It takes a lot to hurt today's stainless steel valves, but in an older car be careful - and an exhaust gas temperature gauge is not a bad idea to invest in.

It is an experimental thing and MORE IS NOT BETTER - less is better until you find the happy medium based the fuel you buy or have in the tank already. 1 oz per gallon - not more than 2 is usually in the right "goldie-locks" range.

Bob,

I am having problems understanding why you say OD is wrong and Rusty is correct, it seems to me you are all saying much the same and that is that gasoline is made up of many components each having different boiling points and the components with the lowest boiling point are the cause of vapour lock.

I have used kerosene to avoid vapor lock and there is no doubt it helps, the more the better up to 20% in a low compression 1920's car. It makes no discernible difference to power but if the conditions are sufficiently adverse it will still vapour lock and then you just have to wait until it cools.

I would like to try IMCT, how is it sold? Is it a product that would be sold by a panel beater's supply shop? Is there a brand name?

In answer to Rusty's comment about adding anti freeze to water, the difference is that water is only one material, H2O, with a single boiling point (varied only by pressure).

I like the attached simple explanation of the issue.

David

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Edited by bobburns
direct name to poster question (see edit history)
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Bob,

<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:PunctuationKerning/> <w:ValidateAgainstSchemas/> <w:SaveIfXMLInvalid>false</w:SaveIfXMLInvalid> <w:IgnoreMixedContent>false</w:IgnoreMixedContent> <w:AlwaysShowPlaceholderText>false</w:AlwaysShowPlaceholderText> <w:Compatibility> <w:BreakWrappedTables/> <w:SnapToGridInCell/> <w:WrapTextWithPunct/> <w:UseAsianBreakRules/> <w:DontGrowAutofit/> </w:Compatibility> <w:BrowserLevel>MicrosoftInternetExplorer4</w:BrowserLevel> </w:WordDocument> </xml><![endif]--> Many thanks for taking the time to clarify this interesting subject . I am intrigued by you statement

"Once these chemicals are blended - the over-all resulting chemical properties - especially boiling point under pressure is changed - they are NO LONGER SEPARATE boiling points in play."

I take this to mean that the separate boiling points of the constituents occur at atmospheric pressure but at higher pressure the resulting mix has a single boiling point. Why does this occur only under increased pressure? We tend to speak of pressure as higher or lower than atmospheric however it is a relative measure and pressure applies under all conditions.

The vapor lock issues that I have are with 1920's Packards where the fuel system is essentially at atmospheric pressure throughout.

They use gravity feed from vacuum tank mounted under the hood and directly over the exhaust manifold. (Maybe this arrangement was intentional to assist in vaporising the fuels of the day but it is all bad in hot weather with today's fuels).

With this set up, pressures throughout system varies only very slightly from atmospheric, lower up to the vacuum tank and higher in the gravity feed from the vacuum tank to the carburettor. Does this mean that we are back to the situation described by OD where the lower boiling point additive reduces only the average boiling point?

You refer to the problem of the additive increasing the propensity for the fuel to self ignite however in my case the compression ratio of the cars is so low (around 4 : 1) that I doubt that it would be a problem. I have used up to 20% kerosene with no discernible change and have spoken to people who told me that years ago on farms these old cars would run fine if started on gasoline then switched to 100% kerosene.

However I would welcome you advice on the following.

I recently fitted an electric fuel pump to one of the cars. Its a bypass arrangement with non return valves to prevent reverse flow and is operated by a switch for use in event of vapor lock. It feeds fuel directly from the tank to the carburettor. The intent being to get "cool" fuel to the carburettor bypassing the areas where the system heats the fuel.

The first opportunity to try it occurred recently. Driving on a warm day in heavy stop start traffic it started vapor locking on a climb - using 10% ethanol fuel with no additive . I switched on the electric pump and it instantly picked up and ran for a few seconds then reverted to the classic vapor lock symptoms. I turned into a side street and opened the hood. The carburettor was flooding, the electric pump was still running. I had hoped that the cooler fuel from the electric pump would solve the problem but it did not. The float has a needle that projects through the top of the carburettor so it is possible to see whether the float is "floating" or not. It was not.

I now think that what was happening was that there was sufficient heat in the carburettor to boil the fuel, the vapor from the boiling increased the pressure above the float preventing it from rising and shutting off the supply. There is clearance around the needle which I would have thought would be enough to vent the increased pressure but maybe not. The other possibility is that it is due to the higher pump pressure. I do not have a pressure regulating valve to reduce the pressure from the pump but it works fine with no flooding under normal conditions and I have fitted a modern soft seat to the float cut off needle.

This experience ties with that the owner of a very early Twin Six Packard. These cars have the carburettor mounted in "V" of the engine with exhaust manifolds running along each side of the carburettor which combined with under hood engine heat makes these cars very susceptible to vapor lock. The owner had tried all practical means to reduce the heat gain of the fuel system but with little improvement. He finally achieved significant improvement by fitting a vent to the carburettor top (which is routed away and under the car for safety). I commented that it was already vented by the clearance around where the float needle projects through the top but he advised that this was not enough and the vent needed to be at least a 1/4" tube and that he could see it venting vapor.

I would welcome your advice on this - with apologies for the length of this post.

David

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Guest bobburns

DavidMC

I am not going to quote all you said, but the flooding from the electric pump was caused by too much fuel pressure over coming the needle seat (or whatever kind of seat it has for the bowl) of the carburetor. Depending on what kind of electric fuel pump you used you will need a regulator - or series of regulators to step down the pressure getting to the carburetor like a Holley 12-803 type at the very least. The 12-803 BP is a By-Pass design of the same style. To avoid extra back pressure on the pump, and to keep cool fuel flow past the lowest pressure point in the fuel system; a by-pass line should be used and it should NOT "dead head" to the carburetor - that is put the return line as close to the carburetor inlet as possible.

There are two kinds and they look the same. One is a deadhead and one is a by-pass. Some can be used for either - or. Lots of Chinese Holley 12-803, 804 etc knock-offs are available.

In a deadhead design the fuel comes into the regulator from the bottom past a check ball which is held open by a pin on the diaphragm. (that is this one in the image below) The adjustment spring under the adjustment screw is pushing down on the diaphragm holding the ball off it's seat. Once the fuel fills up the float bowls in the carburetor and the needles and seats shut, it starts to build pressure, pushing the diaphragm against the adjustment spring under the adjustment screw and allowing the ball to go "up" against the seat, effectively shutting off fuel flow to the carb. There is a light spring that helps push the ball against the the seat in the direction of the fuel flow. The BALL shuts off the fuel flow until the pressure on the other side of it lets fuel get past it to keep the pressure constant

A by-pass style regulator has the fuel coming in the same side of the check ball as where the fuel comes out to the carb. The check ball is held shut with the diaphragm and spring and once the desired fuel pressure builds up it opens that valve and allows fuel to go back to the tank.

I have the one I have set up in a deadhead setup. (see reg-setp.pdf)

This is the same design as a Holley 12-803 or 804 knock off, so I looked up Holley's instructions. => https://www.holley.com/data/<wbr>Products/Technical/199R7914-<wbr>3rev3.pdf

Though I once has it working with only two 0-140 regulators, and since I had messed with the 0-140 regulator on the carb feed side trying to get it to work previously - it popped up to 50 psi - but the 15 psi reg held at 9 psi to the carb - for about 5 minutes, until I tried to reduce the 0-140 below 50 psi.

The point is the 0-140 regulators (they are all coming out of China now-a-days) will not regulate lower than about 20 reliably so you need a staged system - and even Holley says so on the 803BP design set up

I tried to bring the 0-140 pressure feed regulator down to 30 by adjusting the two - to up the return flow and lower the feed pressure - but the 15 psi reg I had just worked on started to climb past 9. Quadrajets should have 6 to 9 at the inlet or they flood past the needle seats. 9 really is max.

When I got it to down to 30 - then the 0-15 psi reg would not hold anymore and climbed to 15 flooding out the engine.

The point being here - you need enough steady high enough pressure on the ball to allow it to regulate down reliably too.

Holley's instructions say, ". . . Loosening the regulator locknut and turning the adjustment screw clockwise increases the pressure. Decrease pressure by turning the adjustment screw counter-clockwise. . . ."

So . . . on this design the adjusting screw all the way out should decrease the pressure the most - IF the ball valve will seat TIGHT

When I adjusted pressure below 30 - it would not seat any longer even with the adjustment screw all the way out

Neither the Holley instructions nor anywhere I can find says what the maximum inlet PSI should be allowed to the regulator - but I was told it was 16 psi and one other spot on the web says something similar. It appears this one needs 40 to 50 minimum.

Of course you may already have this setup - that is the first issue.

THE SECOND ISSUE - the vapor system on the Packard is going to be a problem no matter what today.

Today's fuel is made for high compression engines - and it has an intentionally lower vapor point, with a higher flash point and autoignition point. See also Tom Ogle's "modern" vapor fueling system - google it.

In theory the vapor carburetor was the way to go in that day - with lower flash point fuels like poor grade fuels that all pretty much resembled the weight of kerosene in that early day of motor fuels. Remember STILL transporting fuels was a dangerous thing - and higher grade fuel could just as easily have exploded on it's way to the fueling station or in those glass top hand operated early gas pumps on a hot day.

So with that vapor fueling system - you are stuck "downgrading it" to a lower quality fuel. ESPECIALLY a 10% ethanol blend - once generically called the gasohol summer blend in that vapor system would really be a problem.

LASTLY on your first issue of understanding vapor lock and boiling point. The issue is simple that one is seeking to "re-blend" their own gasoline from one already sold. That is why fuel injection systems push usually 45 to 60 psi on the fuel at all times with a by-pass line - to keep it liquid and keep it moving - so it cannot turn to vapor in the lines.

All petroleum distillates have different chemical properties which change depending on what you mix them with. This is the complex world of Chemistry - which is far too complex to go into here. It is no different than mixing water with ethylene glycol to make what we call anti freeze or with methanol to make windshield washer fluid - you get a completely different product - it is not just water any more; and nor can you separate them back into their original separate entities - so you cannot think of them that way any more either.

reg_setup.pdf

post-88908-143139233281_thumb.jpg

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Bob,

Thanks for the comments, I am aware of the need for a regulating valve to reduce the pump pressure and would have fitted one except that I was advised by the owner of an identical car to mine that his car does not flood using the same electric pump without a regulator, it is only a 2.5 -4 psi pump. Also I fitted a modern soft seat to the carburettor to assist in shutting off the higher pressure from the pump - the original shut off is a brass tapered needle on a brass seat. My car runs and idles fine with no flooding when running with the electric pump, the flooding only occurred once when it vapor locked. I still suspect the flooding was due at least in part to fuel boiling in the carburettor bowl and venting the vapor above the float could assist.

I will be fitting a pressure regulator, it can only help and will have to wait for the next vapor lock to occur to see if it overcomes the flooding.

I think we have hijacked Steve's thread where he asked the question about raising the boiling point of gas which hopefully has been fully answered by these side issues.

David

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Guest bobburns

DavidMC

The Holley 12-804 is a 1 to 4 range PSI regulator. The carb should not flood even with the pump running unless it is putting out enough pressure to over come the float bowl shut off mannerism mechanism of the carb. Another thing you can do is wire the fuel pump to be hot in run and start through an oil pressure switch - so if the motor shuts off or looses oil pressure the fuel pump shuts off too. You can wire a by-pass switch for priming if it is really required.

My last reply.

I do not think we hi-jacked the thread - the article is not even available anymore online to read. He asked about issues and thoughts of what causes vapor lock, so it is just answered in more detail and suggested solutions on how to fix vapor lock.

Edited by bobburns
mis-spelled word (see edit history)
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  • 4 months later...
Guest JWPATE

Boy am I glad to have happened on this thread. Thanks to all contributors, particularly the information from Rusty, Bob and David.

Like many others, I have been considering what to do recently. The '54 Bentley already has an electric SU pump back near the tank, and it's low pressure output is just about right for the two SU H6 type carbs. Everything does just fine, until temperatures rise above 80 degrees or so, as they are soon to do. Never had it act up while running, but since E10 fuel came along it is borderline getting started after hot shutdowns. Usually, just runs really lean for a couple of minutes, and will not go above idle until fresh fuel finally clears through.

I have just this Spring started taking temp. readings of the carb. bowls after each run, just to see exactly at what temperature the problems become apparent. For now, in 70 degrees ambient, the bowls are 100 F. at shut-down and after 15 minutes they rise to 115 F. At these temperatures the engine starts back up fine, but I believe another ten degrees will be in the problem zone.

I have already been thinking about switching over to a modern fuel pump, say the Mallory 110, plumbing in a regulator just downstream of the carbs, and taking the bypass fuel back to the fuel tank. I look upon that effort with a heavy heart though, for I have been religious about keeping the old car original as possible.

So this thread has been a great find for me particularly at this time. Most certainly it will be my plan to fully explore the possibility of "treating the Fuel", with hopes that diesel fuel will make just enough difference to avoid any re-engineering. Most certainly also, should that be successful, I will then experiment with IMCT as well.

Thanks again fellows, for such informative posts.

Edited by JWPATE (see edit history)
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  • 2 months later...
Guest rileybig4

Hi Bob, I can get a hold of some 99.7% pure ethyl acetate cheap. How much should I add to every gallon of gas.I believe they are adding about 5% ethanol to the fuel here. Regards, Mike.

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Guest bobburns
Hi Bob, I can get a hold of some 99.7% pure ethyl acetate cheap. How much should I add to every gallon of gas.I believe they are adding about 5% ethanol to the fuel here. Regards, Mike.

I have no idea - you are in uncharted territory. But it is not the ethyl acetate alone that causes the effect to raise the vapor temperature point of fuel.

Chemistry does NOT work that way - just like adding more any one ingredient to a cake mix will make the cake better

I cannot help you - and no one can without knowing the exact make up of the gasoline being refined where you are.

Bob

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