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Potential vapor luck problem?


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Leaving here Sacramento we endure 100+ temps. I am concerned about the potential problem of vapor lock and the time required to recover from it.

I believe the location of the fuel line is correct as shown in pic.

1) Should I wrap section of line with insulation tape?

2) What is the best way to recover?

 

 

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I don’t believe a vacuum tank can “vapor lock”.  Vapor lock is when gasoline turns to a vapor in a fuel pump.  A fuel pump can pump liquid, but not a gaseous vapor.

 

Your tank uses vacuum to draw gas to tank, then gravity feeds to carb.

 

Make sure you’re vacuum tank is in perfect condition, you should have no issue.

 

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The fuel line can get hot and with this new gas, it can boil and the gas only will flow down the tubing at a low rate. You can idle, but, that is about as fast as you will go. As far as recovery. you will have to shut it off and wait about 10 minutes for it to cool off.

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I have experienced vapor lock with 1920's Packards with vacuum tanks.  I have removed the tank top on the side of the road to see fuel boiling in the tank,  I don't think this stops it flowing to the carburetor but the carburetor is also hot so the fuel continues to boil in the float bowl and flows to the venturi and the engine as a a mixture of liquid and vapor.  The vapor has very little energy so the engine coughs and splutters.  Insulation, heat shield under the vacuum tank help but in 100deg F I would add at least 10% kerosene to the fuel, 20% is better.  I have done it many times.  It usually gets you going but in really hot weather the car is almost impossible to drive.  I once got home by stopping every minute or two on hills to cool the carburetor and vacuum tank with a very wet rag, the problem is much worse on long steep climbs.   I avoid using the cars in very hot weather.  Vapor lock, percolation, fuel boiling call it what you like the effect is the same and its a big PITA in hot weather.  The colder the weather the better they run.

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On my since-sold 1925 Pierce coupe with an aftermarket-of-the era "Gascolator" sediment bowl at the top of the vacuum tank (it came to me that way), I found it necessary to fabricate a jacket made of quilted aluminum heat resistant material sold at performance stores.  Added velcro fasteners for almost-easy on, easy off for show.  The exhaust manifold just below the vac tank on those cars makes the vac tank reservoir a pretty hot place.  Sorry, I don't have a photo to offer.

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Modern gas will boil at 117 degrees.......add a car to being parked on black top...........and then a vacuum tank to draw fuel at such a close number to the boiling point.......you can certainly get vapor lock drawing from the fuel tank to Stewart Warner dash unit. I’m not sure how adding Desiel will effect it.......but was told by a Shell engineer that exclusively worked in auto fuels that it would not help very much.......almost nothing according to the expert. I have no idea.

Edited by edinmass (see edit history)
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I have tried adding diesel, it did not help.  I called a local fuel company many years ago and spoke to technical person.  He told me that kerosene would be much better that diesel and not detrimental.   

The problem is in getting enough kerosene  to make a difference.    As has been said, ethanol fuels are many times worse but its not a new problem, Packard was issuing technical letters back in the early 1930s advising dealers of remedies for vapor lock, its just much worse now with modern more volatile fuels.    I started driving in 1960 and back then certain makes of cars were notorious for vapor lock on hot summer days here. (Australia).  

Incidentally vapor lock has nothing to do with octane rating.

 

 

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I have had the same problem for about three years now and have tried a number of ideas with limited success. a possible problem with modern fuel is slow ignition, resulting in some of the petrol burning in the manifold,this cause overheating, by setting the advance a few degrees more than the manual setting does help.

I am tuning my Senior at the moment and have spent some time making sure the points and spark plugs are in good condition with accent gape setting .Today I will check everything  with my digital timing kit.

Have a read of  Matt's "Restoration of Victory Six sports roadster"? There is a very useful bit about converting his victory six manifold and a senior manifold. Matt has fitted electronic ignition in his car ,I will be doing the same soon.

 

Update.

I took my time and was very careful to get the settings absolutely right (adding 2 degrees of advance) I still need to check all by setting digitally. i took the Dodge for a 10 mile run, driving fairly hard to get the engine nice and hot, no sputtering and  ran very smoothly; it  remains to be seen if it cuts out when idling in traffic. Perhaps using moden speck petrol  means we now need to regularly check our cars are in tune.

Edited by gundog99
update (see edit history)
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I was following a similar thread on another forum and the best alternative offered was to use premium non-ethanol fuel. There is a web site  www.pure-gas.org that lists many of the known locations where non-ethanol gas can be found in the US and Canada. One of the forum members found that he cured his vapour lock problems on a 2500+ mile Michigan - Sacramento run in his Chrysler Airflow this way. When he had to resort to ethanol diluted fuel. the problem came back but disappeared again when he could get non-ethanol fuel. He said the lack of problems made up for the extra cost of premium fuel.

I'm no expert, only reporting what my friend says worked for him. 

Edited by 36 D2 Coupe (see edit history)
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My experience and my comments are only with cars with vacuum tanks, I have not owned later cars with fuel pumps.  I do not want to sound negative but most fixes work on those cars with a low tendency to vapour lock or because the car has not been driven in the conditions that cause vapor lock.  

 I have driven my cars many thousands of miles and they ran fine under most conditions, they  still ran fine in hot weather providing there were no long steep climbs or lots of delays at traffic lights.  Leaving the hood closed after a run then trying to start it while still hot is another potential vaporization condition.

If the car in question does not tend to vapor lock in adverse conditions then just avoiding ethanol is probably all that is needed. 

But if, for example,  it has a vacuum tank right over the exhaust manifold or the carburetor in the "V" between the cylinders such as a an early Twin Six Packard, then it has been my experience that despite adopting all the usual preventative measures, if the conditions are sufficiently adverse, the fuel will occasionally vaporise.   

 I have run my Packards many thousands of miles mostly without a problem but occasionally nothing would prevent vaporisation of the fuel and the consequent problems.  Avoid those driving conditions, fit heat shields etc and there will not be a problem.  

 

How about this for a wild idea to cool the vacuum tank when necessary?   Fit a shroud  around it, and release CO2 from a small concealed CO2 bottle into the shroud to cool the vacuum tank.  This is not a serious suggestion!

Edited by DavidMc (see edit history)
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  • 2 weeks later...

I believe these 29 DB trucks had an insulated fabric on fuel lines. I am using this fabric obtained at Carquest Auto. I also raised the fuel line 1” higher.

Thanks for suggesting different fuel.

Advancing the spark helps also.

I am getting my engine dialed in with short trips.

 

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