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06-04-2010, 10:42 AM | #61 | |
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Re: For vapor lock nonbelievers
Quote:
Thanks for the clarifications and putting us on to the industry standards business. Surely no need to apologize to me for "being so nerdy"; I think of it as providing facts--which is good! In case anyone is interested, there is a bible of-sorts regarding this stuff that you can see through Google Books. Here's the link: http://books.google.com/books?id=J_A...0V%2FL&f=false The vapor lock discussion is around page 78. Also, contains a lot more details about the butane and ethanol issues discussed earlier. The standard involving the temperature at which the vapor/liquid ratio is 20 was apparently developed based on conditions under which diaphragm type fuel pumps for carbureted engines start having issues causing stalling or running rough. I was interested to see that they seem to define "vapor lock" as including running rough. I had assumed it meant engine "locked" or completely shut down. So, I guess I've had more true vapor lock issues than I realized after all. Steve |
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06-04-2010, 05:58 PM | #62 |
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Re: For vapor lock nonbelievers
Thanks, Steve. Another tidbit that might shed more light on these problems: In SAE's Automotive Fuels Reference Book, 2nd Edition, page 180, it explains the phenomenon of Carburetor Foaming: "...caused by the rapid boiling of fuel as it enters a hot carburetor, thereby generating a foam which causes the float to sink. This allows more and more fuel to enter the bowl so that it fills with foam, thereby blocking the air vent and causing an increase in pressure inside the bowl. This pressure increase, in turn, forces excess fuel through the metering jet and vent so that the vehicle suffers similar malfunctions to those caused by vapor lock, even though they are caused by excessive enrichment of the mixture rather than the overleaning that occurs with vapor lock. In cases where the vent goes directly to atmosphere, fuel can be forced out into the engine compartment and cause a fire hazard." Sound familiar? I do remember vapor lock (or was it carb foaming?) problems with my diaphragm fuel pump small block Chevy with lopey cam, headers, etc. until I installed an electric fuel pump in the trunk to feed it. Problem solved. I spoke with several Model A folks from our club today at a car show and they have seen bubbles in clear filters and one had fuel bubble from the carburetor vent on their engines, but neither experienced vapor lock. Hmmm.
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06-04-2010, 08:08 PM | #63 | |
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Re: For vapor lock nonbelievers
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The phenomenom you describe above is commonly referred to in the MoToR's and Chilton's manuals of the '40s & '50s, as "percolation", and was a fairly common problem with down-draft carbs. This is the first time I've heard it described as "foaming", but the symptoms jive with percolation. The only vehicles I had a consistent percolation problem with were 216 & 235 Chevy sixes running the Rochester B carburetor. When it occurred, it was always as a "hot start" problem: come back to the vehicle after a five or ten minute stop in hot weather, and the engine doesn't want to start. The "smoking gun" is when the vehicle finally starts, it usually belches a cloud of black smoke until the excess fuel is cleared. |
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06-04-2010, 08:26 PM | #64 | |
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Re: For vapor lock nonbelievers
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Please give me and the "non believers" the reason the guys you spoke to in your club That didn't experience vapor lock. On another note I was out driving today in 90 degree weather with the same crap fuel everybody else uses in stop and go traffic and my car ran fine. I did notice that temperature of the coolant went as high as 185 degrees. I'm going to wait until we get a really hot day and I'm going to clamp the wife's oven thermometer to the fuel line and see what the fuel line/engine compartment is running at. I'm just curious. I will post the results when that happens.
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06-05-2010, 10:56 AM | #65 |
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Re: For vapor lock nonbelievers
Good idea. I bought a Sears IR thermometer to solve another problem and will take it with me today to be in parade in Florida, NY. It's hot and humid (bet we get wet) and will check the temp of fuel at the filter, line, and carburetor right after. I'll be with the club member who experienced the boiling through the vent during a parade. That turned ugly when he took off from a stop with spark retarded, heard a backfire, and found his carburetor was on fire! With a carburetor attached to a cast iron intake manifold attached to a cast iron exhaust manifold and no cooling air flow, things can get nasty in a hurry. More to come....
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06-05-2010, 07:05 PM | #66 |
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Re: For vapor lock nonbelievers
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06-05-2010, 08:31 PM | #67 |
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Re: For vapor lock nonbelievers
Thanks for the information. Tomorrow I'm supposed to go to a car show/swap meet at Flowrerfield in St. James. Perhaps we'll have the same weather as today on Long Island (Hot & Humid). I'll try to run the same test as you did and post the results.
I'm posting pictures of my arsenal of tools for the test.
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"Some Talk the Walk while others Walk the Walk" Last edited by Bob A.; 08-04-2010 at 09:30 AM. |
06-05-2010, 09:05 PM | #68 | |
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Re: For vapor lock nonbelievers
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06-06-2010, 08:19 AM | #69 |
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Re: For vapor lock nonbelievers
check the steel fuel line to see if it is absolutely clear of rust particles sticking to the walls of the tubing , as the gas flows past it will create turbulance and drag on the fuel as it passes over the obstruction.
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06-06-2010, 03:18 PM | #70 |
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Re: For vapor lock nonbelievers
Well I was somewhat disappointed today, No traffic and not so hot for my test. These are my results:
Glass bowl Temp. 108* Steel fuel line 151* Carburetor 141* Upper Radiator surface 179* Ambient temperature 84* and very humid Highway temp. running ( fuel line) 116* Although some temperatures match "Olds182", It just wasn't hot enough. The wife won't let me use her oven thermometer anymore, she told me she'll take my temperature with it if I tried again!!! I'm posting some actual pictures while I was driving.I took one when I was Idling for twenty minutes with the spark retarded all other times the spark was advanced about 5/8's down. . You can tell by the speedometer and temperature gauges what was going on.
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"Some Talk the Walk while others Walk the Walk" Last edited by Bob A.; 08-04-2010 at 09:30 AM. |
06-06-2010, 03:30 PM | #71 |
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Re: For vapor lock nonbelievers
and shes not going to take your temperature orally either
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06-06-2010, 04:16 PM | #72 |
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Re: For vapor lock nonbelievers
ouch!!!
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06-07-2010, 10:22 AM | #73 |
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Re: For vapor lock nonbelievers
This my first post on the new Ford Barn. Finally I was approved today. There have been several very good posts by people who obviously have some Chemical Engineering experience that are leading them in the right direction. I have more than 30 years experience in the refining industry, mostly in gasoline component refining for a company that licenses refining processes.
There are many factors involved in formulating gasoline. Gasoline is formulated for modern cars with fuel injection and pumps in the tank. This increases the fuel pressure. Higher pressure will inhibit vaporization. Modern cars have high underhood temperatures, higher than our Model A's. The important factor to consider is Reid Vapor Pressure (RVP). Over the last 25-30 years refiners have had to control RVP at the direction of the EPA. RVP is a variable that is somewhat different for every market in the US. The addition of various components will change the vapor pressure. The best components are most expensive. A few tenths of a cent per gallon really makes a difference in the refiners cost and the profitability of the single most important product of any refinery. You should use an infrared non-contact thermometer to take the temperature at various places in the engine compartment, especially the carburator bowl just after shutting off the engine. I expect that the temperature will show a drop as the gasoline in the carburator bowl is boiled off. This should happen in cars that show problems with "vapor lock". I have just written an article for the Smoky Mountain Model A Club that will be published in a few weeks. There is enough interest in this subject that I should do some hands on research and review the written materials prior to writing an article for one of our magazines. This might take a few months. I hope that it will be published by the end of the year. Meanwhile, if you are experiencing problems or want to do a little preventative work for vapor lock insurance you should insulate your fuel line with rubber fuel hose and flex electric loom over the rubber line. Carefully split the rubber line and install it on the metal line. I am looking at a light gauge metal shroud for the carburator. All of this should be easily removable for judging. Any comments are welcome, either directly to me or by posting them. Thanks. Vic in E-TN |
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