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  #21  
Old 03-13-2017, 05:49 PM
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My post assumed you have a Squarebird but the information I gave about venting still stands. You don't want a pressurized gas tank, ever.

New cars draw a vacuum on the fuel tank to make sure there is no pressure. They capture and burn those fumes, not because the smell of raw gas is nasty but because it is explosive.

Your fuel tank should never produce so much pressure that it blows gasoline past your carb's needle valves. Remember, the fuel line delivers liquid gasoline, not fumes. Those little floats cannot stop more than six pounds of pressure, otherwise they spew into the bowls, out the vents, and onto your hot engine.

If your tank is not vented, to prevent pressure buildup use a vented gas cap. - Dave
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  #22  
Old 04-14-2017, 02:08 PM
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Default Moved Fuel Line, but still get stalls

Here's a pic of the new fuel line. It's up off the engine and insulated from the heat. Nonetheless after warmed-up and then turned off, the car will stall after restart.

What I've noticed is that when that happens, the fuel filter will not fill, even with just the fuel pump on (refer to 2nd pic). My theory is that the unfilled part of the filter is a pressurized vapor keeping the filter from filling with liquid.

What about the carburetor? Could it be I need to put a thermal block between the carb and the aluminum intake manifold?
Attached Images
File Type: jpg NewFuelLine.jpg (622.5 KB, 101 views)
File Type: jpg FuelFilter.jpg (194.6 KB, 150 views)
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  #23  
Old 04-14-2017, 02:28 PM
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Did you ever get a vented gas cap. Remove the cap to relieve the pressure and then see if it will pump.

John
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  #24  
Old 04-14-2017, 06:57 PM
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Quote:
Originally Posted by HighwayThunder View Post
Here's a pic of the new fuel line. It's up off the engine and insulated from the heat. Nonetheless after warmed-up and then turned off, the car will stall after restart.

What I've noticed is that when that happens, the fuel filter will not fill, even with just the fuel pump on (refer to 2nd pic). My theory is that the unfilled part of the filter is a pressurized vapor keeping the filter from filling with liquid.

What about the carburetor? Could it be I need to put a thermal block between the carb and the aluminum intake manifold?
I doubt your theory re the 'pressurised vapour' however in any event I would have put the filter on that vertical section of fuel line above the fuel pump.
If it WAS vapour under pressure in the filter it would vent itself through the carb as soon as the fuel in the fuel bowl dropped its level.

I also doubt the necessity to put in a thermal block.

My 2 cents worth.
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  #25  
Old 04-15-2017, 09:50 PM
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I see Street Demon carbs need a bigger accelerator squirt nozzle when using larger cams and more cubic inches. The standard nozzle is .031 in size. Some of the symptoms you describe are caused by the above nozzle or bad vacuum.
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  #26  
Old 04-27-2017, 12:29 PM
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Default Cavitation

I noticed that my feed tube to the fuel pump is 5/16". The main tube running under the car is 3/8", and the new tube I installed over the engine is 5/16". I mentioned this to an ME as a possible cause of the problem. He immediately suggested it could be a cavitation problem.

"The cavitation phenomena occur in regions where large pressure drops results in the local pressure falling below the vapor pressure, resulting in formation of vapor bubbles. Typically for pumps, cavitation occurs in the suction side of the pump blades, which in turn results in a reduction of effective area of the blade, thereby diminishing the efficiency of the pumps."
(SAE, Predicting cavitation in fuel pumps, 03-Jan-2014, http://articles.sae.org/12709/)
Causes of Cavitation:
"Having the pump at too high of a distance above the fluid source
Having too small of a diameter of suction pipe
Having too long of a distance of suction pipe
Having too many fittings on the suction pipe
Handling a liquid with a low vapor pressure
Running the pump too fast"

(Dale Conway, Pump cavitation diagnosis and control, 2/18/2010, http://www.flowcontrolnetwork.com/qa...nosis-control/)

I'm going to replace the 5/16" tubing with 3/8" and re-test.

Cheers,
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  #27  
Old 04-27-2017, 05:48 PM
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You don't have cavitation, or vapor lock. OEM fuel pumps are diaphragm-type so there is no high speed vanes or blades. We never heard a word about taking John's suggestion in regards to the tank cap. Aside from all that, your car and millions of others worked perfectly fine from the factory and for many years.

You MAY have:
A restricted pickup screen,
A collapsed fuel line,
A pinched fuel line,
Carb issues.

Your engine will run around town nicely with a 1/4" fuel line. - Dave
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  #28  
Old 04-28-2017, 09:36 AM
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Quote:
Originally Posted by HighwayThunder View Post
What about the carburetor? Could it be I need to put a thermal block between the carb and the aluminum intake manifold?
No it does not. I've run these exact carbs on large mud trucks
that the radiator is clogged with mud, truck was pushing 230 and
have had zero problems with heat from the carb.

Get a cheap electric fuel pump and mount it right in front
of fuel tank. I did this due to the "pushrod" that is required
for the funky 430 fuel pump actuation.

If you want fuel lines to look authentic (on the 430, the
upside down fuel pump on top front of engine is a nice
conversation piece), you can run fake lines (I did) in
and out of pump and "hide" real fuel line coming up back of engine.
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  #29  
Old 04-29-2017, 04:05 PM
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Default Stock Ignition?

HIGHWAY Thunder,, still stock ignition?? sounds like condenser prob or if electonic , bad ignition module..if you still suspect fuel related,,,you MUST put guages on and t/shoot that system completely. This type of prob can drive you to selling car and the growin Roses for a hobby CHEERS TERRY
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  #30  
Old 04-29-2017, 06:05 PM
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Quote:
Originally Posted by HighwayThunder View Post
...What I've noticed is that when that happens, the fuel filter will not fill, even with just the fuel pump on (refer to 2nd pic). My theory is that the unfilled part of the filter is a pressurized vapor keeping the filter from filling with liquid...


Your float bowls are vented to the carb throat. The floats only close-off supply when enough LIQUID gasoline lifts the floats. A constant flow of gasses will simply vent out past the needle valve as it remains open until the float closes it. - Dave
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