Author Topic: vapor lock  (Read 1805 times)

Offline fwjack

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vapor lock
« on: May 22, 2012, 07:50:17 AM »
I own 1932  and 1941 Cadillacs, both are V8's. Any suggestions on how to deal with vapor lock? Engines start fine when cold, but not after running at 50 mph for an hour.
Thanks,
Fred Jackson
Fred Jackson

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Offline Bill Ingler #7799

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Re: vapor lock
« Reply #1 on: May 22, 2012, 04:17:07 PM »
Hi Fred: Vapor lock has had so many postings over the years I would be safe in saying it takes the number one spot on what has appeared on this forum. To answer your question I first would go up to the top of of this page and click on search. Then type in Vapor Lock. You will probably get 3 or 4 pages of answers on vapor lock. If you still need to get an answer for your vapor lock question, please post again and I am sure you will get many replies.  Bill

Online 47bigcadillac

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Re: vapor lock
« Reply #2 on: May 23, 2012, 07:57:13 AM »
Fred, I also happen to own a 1932 Cadillac V8 and a 1947, both same engine as yours.

I did quite a lot of work on the 1932 to fix the percolation issues with modern gasoline, which is what your problem sounds like, rather than vapor lock, which more rare and depends on where you drive (heat and elevation)

I can go over the list of things I did to those cars but before that, can you perhaps explain more in details the symptoms and how/when the issues appears.

Rob
« Last Edit: May 23, 2012, 07:59:07 AM by 47bigcadillac »
R. Brandys
e-mail   47@bigcadillac.com

1932 355B  Victoria Coupe            
1935 LaSalle Coupe  5077
1946 Club Coupe      6207
1947 Club Coupe      6207

Offline fwjack

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Re: vapor lock
« Reply #3 on: May 25, 2012, 06:15:20 PM »
Thanks for your answer Rob - My hard starting only happens after a half to one hour drive doing 55mph. If I try to start the car after shutting it off, it won't start. I have an Optima battery and the motor is completely stock. Once cooled down, it starts fine. By the way, you have good taste in old cars!!

Fred J.
Fred Jackson

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Offline fwjack

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Re: vapor lock
« Reply #4 on: May 25, 2012, 06:20:47 PM »
Thanks for your help, Bill. I guess I am not the only one with the problem.

Fred J
Fred Jackson

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Online 47bigcadillac

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Re: vapor lock
« Reply #5 on: May 29, 2012, 06:02:59 AM »
Fred,
The goal is to bring the gasoline temperature down. Easy on the 346, harder on the 355b.

The 355B intake is mated to the exhaust headers, and in the middle of it, with hot air blowing from the fan right into the carb and filter as a bonus.
The 355B carb has a very long neck so that hot air from the fan and engine bay will heat it up over time.

Gasoline in the early 30's must have been very heavy stuff to require such a setup.

My 1932 car engine did stop a few times in traffic, at low RPM so I had to take some drastic measures to avoid blocking everyone for the next 30 minutes. I could smell the gasoline before the engine would quit.

Here is what I did:

1) draw cool air from the bottom - this had by far the greatest impact on reducing percolation
2) wrap the fuel lines, fuel pump and carb in heat reflecting material.
3) Place a phenolic spacer between the carb and intake - not much space in there but every step helps
Also, another thing to keep in mind: high octane gasoline does boil at lower temp than low octane, and winter/summer gasoline formulation does change quite a bit; my problems were worse in winter (lighter gasoline).

Here are the photos for the 355B
http://cadillac.gs/1932engine/

For the 346, just wrap the header behind the carb and the fuel line from the pump to the carb, maybe the pump as well. That should be sufficient as the percolation is not that big of an issue on these engines. The intake is separated from the exhaust and the carb neck is short.
The original metal air filter is also a way to gather heat, beside poor air filtration I use the K&N filters in all my cars, they have so many shapes which fits any car.

http://cadillac.gs/1947engine/engine-left1.JPG

Rob
« Last Edit: May 29, 2012, 06:12:48 AM by 47bigcadillac »
R. Brandys
e-mail   47@bigcadillac.com

1932 355B  Victoria Coupe            
1935 LaSalle Coupe  5077
1946 Club Coupe      6207
1947 Club Coupe      6207

Offline fwjack

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Re: vapor lock
« Reply #6 on: June 01, 2012, 06:57:20 PM »
Thanks again, Rob - I will go to work on these suggestions.

Fred J
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Offline Classic

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Re: vapor lock
« Reply #7 on: June 01, 2012, 08:45:19 PM »
Some thoughts and questions about vapor lock:

1.   I believe the 1937-48 flat head V8s have exhaust crossover passage in the INTAKE manifold that runs under the carburetor.  I assume this was included to provide heat under the carburetor to help vaporize the low quality fuels available back then.  Today's fuels vaporize easily without assistance.  So can this exhaust passage be blocked to reduce heat going to the carburetor?  One way to block the passage could be to use a thin metal plate on each end of the passage where the intake manifold bolts to the block.  I suspect the 32 V8 has a similar carburetor heating arrangement.

2.   I have heard of people adding a small amount of kerosene or diesel fuel to gasoline to reduce its volatility.  Has anyone tried this?  Does it work?  What ratio should be used?

3.   There is an in-line fuel filter with a 3rd port to allow a portion of the fuel to return to the fuel tank.  An example is a Fram G3587:  http://shopping.yahoo.com/751510533-g3587-fram-filter-g3587/  Installed between the fuel pump and carburetor, this would allow cooler fuel to continue to circulate through the fuel line and fuel pump.  Of course that would mean adding a return port to the fuel tank.  Has anyone tried this?

What do you experts think?
Gene Menne
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Online 47bigcadillac

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Re: vapor lock
« Reply #8 on: June 02, 2012, 09:43:20 AM »
Interesting ideas

#2. I have never tried kerosene because It may create more carbon deposits and other more critical issues down the road.


Today's fuel are not all bad for our classic cars - high-octane gas (non ethanol) evaporates very clean without any gumming the valves or carb, which suits cars not driven often.

#3 not sure how this will solve gasoline boiling inside the car, and this won't work once the cars stops and heats build up.



R. Brandys
e-mail   47@bigcadillac.com

1932 355B  Victoria Coupe            
1935 LaSalle Coupe  5077
1946 Club Coupe      6207
1947 Club Coupe      6207

Offline Bill Ingler #7799

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Re: vapor lock
« Reply #9 on: June 02, 2012, 02:37:32 PM »
Hi Fred: Here is one idea which might help you get started again after the 346 has been shut off after a hot run. I use my electric aux fuel pump for 3 things. To fill the lines,engine pump and carb after the car has been setting many days since the last start. I use the electric pump when I have a vapor lock while driving. I also use the electric pump to start a hot car. As you probably have seen after shutting off the engine after a hot run, the fuel is boiling in the lines and the fuel pump. Peculation of the the fuel leaves the lines empty, the engine fuel pump/ carb are probably low on fuel and you probably could have a vapor lock in the engine pump.  With a hot engine re-start I turn on the electric pump, wait about 20 seconds, VERY GENTLY push the gas pedal about 1/2 way down and push the start button. With the aux pump on for the 20 seconds, it fills the engine pump as well as the lines and the carb, plus knocking out any vapor lock. With the 1/2 accelerator this gives a better fuel/air ratio for starting. You might need to experiment with the position of the accelerator as my 41 need only about a 1/4 pedal while my 47 needed the 1/2.  Wrapping the line between the engine pump and the carb didn`t do a thing for me. Remember this line is the only line under pressure. The engine fuel pump is putting out 4-5 pounds of pressure which should be more than enough to prevent a vapor lock in this line. More than likely a vapor lock is going to happen in the bottom of the engine pump and in the line from the tank as that is where you have the lowest pressure drawing the fuel from the tank. This is only part of starting a hot car. A good battery, the right battery cables and a good starter are also needed. Have fun     Bill

Offline fwjack

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Re: vapor lock
« Reply #10 on: June 03, 2012, 06:54:15 PM »
Sounds like a logical solution and an easy and inexpensive one to try. Thanks for your input.

Fred J.
Fred Jackson

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Offline Jay Friedman

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Re: vapor lock
« Reply #11 on: June 04, 2012, 10:10:10 AM »
To add to what Bill Ingler said about the right battery, cables etc., in a 6 volt car good grounds and a "fat" positive (or negative if pre-war) battery cable are needed to solve the starting problem described.

I suggest the following:

1. Have the starter motor rebuilt with heavy duty field coils.  Scrape off any paint on the surfaces where the starter and engine meet;
2. Get the thickest positive battery cable possible.  I think they are called 00 gauge.  I had mine made up from 600 volt welding cable;
3. Get a new negative battery cable and make sure all the small ground straps are clean.  Scrape any paint off ground contact points;
4. Get a (6 volt) battery of at least 600 cold cranking amps.  I use an Optima which has 850 cold cranking amps (which are now available at amazon.com for $125 or so).
1949 Cadillac 6107

Offline jaxops

  • Mark Monaghan
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Re: vapor lock
« Reply #12 on: June 10, 2012, 05:04:54 AM »
I would add to this suggestion that you add some SeaFoam to the fuel to help ameliorate the alcohol in the gasoline, unless you're in a state where that wasn't mandated.



Fred,
The goal is to bring the gasoline temperature down. Easy on the 346, harder on the 355b.

The 355B intake is mated to the exhaust headers, and in the middle of it, with hot air blowing from the fan right into the carb and filter as a bonus.
The 355B carb has a very long neck so that hot air from the fan and engine bay will heat it up over time.

Gasoline in the early 30's must have been very heavy stuff to require such a setup.

My 1932 car engine did stop a few times in traffic, at low RPM so I had to take some drastic measures to avoid blocking everyone for the next 30 minutes. I could smell the gasoline before the engine would quit.

Here is what I did:

1) draw cool air from the bottom - this had by far the greatest impact on reducing percolation
2) wrap the fuel lines, fuel pump and carb in heat reflecting material.
3) Place a phenolic spacer between the carb and intake - not much space in there but every step helps
Also, another thing to keep in mind: high octane gasoline does boil at lower temp than low octane, and winter/summer gasoline formulation does change quite a bit; my problems were worse in winter (lighter gasoline).

Here are the photos for the 355B
http://cadillac.gs/1932engine/

For the 346, just wrap the header behind the carb and the fuel line from the pump to the carb, maybe the pump as well. That should be sufficient as the percolation is not that big of an issue on these engines. The intake is separated from the exhaust and the carb neck is short.
The original metal air filter is also a way to gather heat, beside poor air filtration I use the K&N filters in all my cars, they have so many shapes which fits any car.

http://cadillac.gs/1947engine/engine-left1.JPG

Rob
1970 Buick Electra Convertible
1956 Cadillac Series 75 Limousine
1989 Ford Crown Victoria Station Wagon
1997 Lincoln Town Car
AACA, Cadillac-LaSalle Club #24591, ASWOA

 



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