vapor locking question...

ok, so i bought my girl a '55 ford with the stock 223 straight six with a three carb. setup and split exhaust that i did not install, the fuel delivery system is made up of metal tubing from about the frame all the way to the carbs, and brass fittings from home depot or something.

one time at the hottest point of last summer the car acted as if it was out of gas, sputtering, then stalled and would not immediately restart. we determined it to be vapor lock.

now, i remember when i was younger my father told me they used to wrap short lengths of wire around a fuel line with the ends sticking out to act as a heat sink. in my mind, that sounds like it would help, but damn that would look ugly!
i already have a nice, OLD fuel distribution block that would look good mounted behind the long finned valve cover that's on this car. i wanna use it and run flexible hose to each carb from it.

whew! my question is, how much would this help alleviate vapor lock, and if not much what else can i do to help other than move from the desert to a cooler climate?

thank you.
tred.

 

Put a return line to the tank on it,the constant fuel flow will slove the vapor lock issue, did it several years ago on my Ranchero. Mopar fuel filters had a 3rd line built in for just that purpose,there are others like that also.

 

very cool, thank you johnevans.

 

Great tip, thanks!

 

Keep in mind that technically, vapor lock only occurs on the suction side of the fuel pump. By design, mechanical fuel pumps are primarily designed to pump only liquid fuel. They are less suited to pumping air, and this is a particular problem on the suction side of the pump. Air in the pump inlet line is compressible and the pump pretty much just compresses and expands this air without actually moving much liquid fuel into the pump. And it only gets worse if it's an old pump that's not working up to specs anymore.

On the outlet side of the pump, the pressure side, a bit of air in the fuel line is much less of a problem. If there is liquid fuel going into the pump it's very easily pressurized and will push fuel, and any air bubbles, thru the pump outlet pipe and on up to the carburetor. It's still a good idea to keep these lines away from heat sources, and maybe add an insulator or heat dissapater to the base of the carb. But heat issues on this side of the pump cause a whole different set of issues like fuel percolation and gas escaping from the carburetor vent tubes.

Heat isn't the only cause of air getting into the suction side of the fuel lines. Also check the steel lines and rubber hoses for good connections, holes, rust perforation, splits and cracks. You won't necessarily see any fuel leaks or smell gas since this section of line is normally at atmospheric pressure or under a slight vacuum. A hole can let air enter the line without allowing fuel to escape.

 

ok I am not jokeing, I hear back in the day you could put cloth pins on fuel line for vapor locking,

 

Yep! And it could very likely help cure the problem. The clothes pins acted like a heat sink and helped draw heat away from the fuel and fuel line. Sometimes you'd also see pieces of aluminum foil wrapped loosely around the fuel line to do the same thing.

 

I did all that shit back in the early 60s...tin foil, clothes pins, etc. etc. Nothing worked. I did not have a vapor lock problem but I believed all the vapor lock BS too. I was a kid. My problem turned out to be a failing coil. Before you spend a lot of money have an experienced mechanic make sure you have a vapor lock problem. Lots of people have wasted a lot of money chasing wild geese. Every time a car acts up in the heat the locals are quick to say vapor lock. I've never experienced it in all my years.

 

duely noted.

i've had the car out here in downtown hell for years, and never before and not since has it acted this way. my plymouth has an 8 gallon spun aluminum gas tank and no gas gauge, i've have run it out of gas many times, i know exactly how it acts. the ford felt the same way but had at least 3/4 of a tank of gas in it. also, i was following someone driving about 25 mph for about 9 miles (no real air flow across the engine) in 120+ degree heat.
after letting the car sit for a couple hours, it fired right back up and it's been smooth sailing ever since.

maybe i misspeak when i call it vapor lock, but i'm wondering if the fuel in the metal fuel lines was partially evaporating(?) before it got to the carbs. due to all the extra heat in the engine compartment...

 

Clothes pins are really not that expensive and don't take too long to install just to see IF that is your problem. Dad had a 48 Chrysler that would vapor lock without fail traveling through Arizona. When I first got my new Camaro in '67, it also vapor locked and a clothes pin on the metal fuel line between the pump and carb fixed it. I mean how much more old school can you get?

 

I'd try it for a while to see if it is a recurring problem.

 

well, my original purpose for this thread was to find out if i use flexible fuel line, maybe even the translucent red ones that you see a lot of, would there be any additional heat introduced to the fuel, and if not, would this actually help prevent vapor lock to a small degree?



thank you all for your help.
tred.

 

That red fuel line breaks down with modern gasoline.

 

yeah, i've heard that before.

i'll find something that looks good with that engine/setup.

 

Try purging the fuel tank vent line and check that you have the right gas cap. It could be as simple as that?

 

I've heard that vapor lock is BS, but I have to stick with my personal experience.

Back in high school, my 54 Ford would sometimes refuse to start if I'd driven the car, stopped briefly to run in to a store or something, and then jumped back in it.

My dad told me it was vapor locking and said I should replace most of the metal fuel line in the engine bay with rubber.

I did and it never did it again.

 

Sure-fire and quick way to tell if its vapour lock- carry a couple of rags and a bottle of water- when the motor starts playing up, wrap the fuel line with the rags, pour water on it . All you have done is cool the fuel in the line, letting it condense into a liquid again. If it works, then you can insulate or re-route your fuel line. Or install an electric pump (at the tank end).

 

that's exactly what we did after a drenching walk to the store for some water.
...and next to a large pig farm! oof!

 

i've been thru the same thing. coil ended up being the problem.

 

for all the Vapor lock theorist How come all the same make and model cars with the steel fuel lines don't have the same problem every time it gets hot? It seems to me that there would be an ass load of clothespins missing.

 

epa gas is most of the problem

 

Vapor lock occurs when NPSHr (net positive suction head) "required" (a function of pump design/condition exceeds the NPSHa available, a function of the system at the time. The system includes several factors like tank level, fluid temperature, plumbing restrictions, altitude, gasoline makeup,etc. Components of gasoline begin to boil near 100*F. Vapor lock is a very real factor in chemical engineering. Wood or plastic clothespins have a very low thermal conductivity...not very much help

 

For the non-believers; Why did the manufacturers put return line systems in vehicles?

 

i use a can of FREEZE_IT its use to detectbad transistors and other electronic components.Its like freon in a can .I keep a can in the trunk.

 

the wood or plastic is not the heat sink, but rather the metal spring is. still, i can't see it helping matters much.


...and your point about fuel components beginning to fail makes me think i had a different issue that day...

 

A quote from Air BP on avgas versus mogas. Apparently they believe vapor lock exist.
Volatility.

http://www.bp.com/sectiongenericarticle.do?categoryId=4503701&contentId=57723


A gasoline engine requires a fuel which is sufficiently volatile to allow easy formation of the air and fuel vapor mixture required for combustion, while not being so volatile as to cause bubbles of vapor in the fuel lines ("vapor lock") resulting in fuel starvation. Specifications are set to control these properties based on the fuel's vapor pressure and distillation characteristics. These are different for Mogas and AVGAS.








After manufacture, small amounts of approved ethers and alcohols may be added as fuel system anti-icing additives. However, this is strictly controlled to meet particular operational requirements. High concentration of alcohols can attack fuel system components and cause seal swelling/failure. They can entrain water into the fuel and promote phase separation into water + alcohol/fuel phases, which may cause engine failure. AVGAS specifications help protect the aviator from these hazards.
AVGAS, and other aviation fuels, are very carefully controlled at the refinery and in the distribution system to ensure no contamination by other products. Red, green and blue dye, respectively, are added to distinguish between AVGAS 80, 100 and 100LL for instance. Quality control follows every batch ensuring it is clean and on specification, ready for use. Overall, AVGAS is the highest quality gasoline a refinery can manufacture.