Vapor lock!

[steve s]

Originally Posted by Milton

Steve,
This is a prime example of surface tension, however, in this example the root cause of the trapped air bubble is usually a non-operational vent pipe. If the drain is properly vented the vents can sometimes accumulate leaves in the pipe and cease to work properly.

Milton,

I know what you're saying, but in the case I deal with daily, it's a fairly new, well vented, construction. The problem is that a decorative covering on the stopper narrows the drainage gap just a tad. The plumber pointed out to me what was going to happen when he did the installation. He demonstrated the flow difference with and without the cover. Maybe an issue with Delta. Sounds a bit off-topic but I still think it's great example of the point I was trying to make.

Steve

[Milton]

Steve,
I certainly agree with you about the example. I have yet to hear from BRENT in 10-uh-C but, other than that, I feel comportable with our findings here and figure that, unlike Float A Motors and oil, we just might have put this topic to sleep.

[BILL WILLIAMSON]

Wherever or whatever is causing these problems, to me, seems to be related to underhood temps. I wonder if it is either more or less prevalent with different fan configurations??? Studying the carb top filter chamber, I strongly believe that boiling gas in there can't escape through the needle & seat & backs up into the gas line causing no fuel flow. If this could be he root cause, the next challenge would be to keep that chamber area cooler.
Before OSHA & all these GREEN PEOPLE, Ol'Bill might have imagined, "If someone makes a self adhering asbestos putty-like goop, I'll layer it on that area to keep it cool & paint it flat black!" Wish I could talk to Chief, I'll bet you this is not just a "modern day" problem!! Bill W.

[Tom Wesenberg]

Originally Posted by BILL WILLIAMSON

Wherever or whatever is causing these problems, to me, seems to be related to underhood temps. I wonder if it is either more or less prevalent with different fan configurations??? Studying the carb top filter chamber, I strongly believe that boiling gas in there can't escape through the needle & seat & backs up into the gas line causing no fuel flow. If this could be he root cause, the next challenge would be to keep that chamber area cooler.
Before OSHA & all these GREEN PEOPLE, Ol'Bill might have imagined, "If someone makes a self adhering asbestos putty-like goop, I'll layer it on that area to keep it cool & paint it flat black!" Wish I could talk to Chief, I'll bet you this is not just a "modern day" problem!! Bill W.

Why paint it black?
When you want to radiate the heat AWAY from an INTERNAL source, such as a motorcycle cylinder, then flat black works best.

When you want to reflect heat away from an external source, such as the Model A exhaust manifold, white works best. That's why I was lucky to find a white plastic covering that fit over my fuel line when I was using the crap gas. With good gas, I removed the cover and keep it under the rear seat.

[BILL WILLIAMSON]

Originally Posted by Tom Wesenberg

Why paint it black?
When you want to radiate the heat AWAY from an INTERNAL source, such as a motorcycle cylinder, then flat black works best.

When you want to reflect heat away from an external source, such as the Model A exhaust manifold, white works best. That's why I was lucky to find a white plastic covering that fit over my fuel line when I was using the crap gas. With good gas, I removed the cover and keep it under the rear seat.

The black was for asthetics & Fine Points Judging.
Tom, Your comment about my reputation was the nicest thing anyone could have said to me today, even surpassing Gregg saying, "Hey,Dad, got your Burgundy Wine, you forgot to put it on your list!"
Bill W.

[Blessyouboys]

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Originally Posted by BILL WILLIAMSON

Before OSHA & all these GREEN PEOPLE, Ol'Bill might have imagined, "If someone makes a self adhering asbestos putty-like goop, I'll layer it on that area to keep it cool & paint it flat black!"

What area do you want to cover with putty-like goop?

[steve s]

Originally Posted by BILL WILLIAMSON

...Studying the carb top filter chamber, I strongly believe that boiling gas in there can't escape through the needle & seat & backs up into the gas line causing no fuel flow. If this could be he root cause, the next challenge would be to keep that chamber area cooler. ...

Bill,

I don't know about your black goop, and I've got Cling's radiator fan in my car and believe vapor lock problems occurs with all kinds of fans. However, I bet you have hit on an important factor--a vapor bubble in that screen chamber, with the only ways out thru smaller orifices, is a perfect setup for a metastable bubble blockage. Briefly cracking the gas line fitting could disturb the situation enough to allow gravity to take back over again--probably even cooling things down a bit too, as dribbled gasoline evaporated.

Steve

[Duffy1]

I have not tried it yet ,but an earlier post suggested shutting off the gas valve and run all the gas out of the carburator if you are stopping some where and plan to stay lets say over 30 min which by my expariece is how long it takes for the gas to vaporize in the carburator . When you are ready to leave open the valve fresh cool gas into a cooled down carburator should solve the problem . Next time I am out I am going to try this . I did the choke drill and it worked although it was not fun in a lot of traffic ,but a lot better than dieing out in the traffic .

[Milton]

Now that I am a believer of Model A vapor lock I have to ask why. These cars did not come from the factory with a distributor or carburator heat shield so why the need now? I live inland from San Diego up a three mile 7% grade and in the summer my community is called Hell Cajon, yet I have NEVER experienced a vapor lock in an A. In the thirties these cars were overloaded beyond belief yet made the trip from the dust bowl through the desert to California, how? Methinks there is a cause beyond gasoline, cast iron carbs, etc., retarded timing could do it, lean fuel mixture, what else can cause extreme manifold heat? Anyone?

[BILL WILLIAMSON]

Originally Posted by Blessyouboys

What area do you want to cover with putty-like goop?

That raised area on top of the carb where the screen filter resides. Bill W.

[Tom Wesenberg]

In the "good old days" they didn't have to fight the bad effects of ethanol. My 28 has the fan shroud, original fan, carb, manifolds and 4.2 head and only has problems if the temp is over 80 and if I have 10% ethanol crap gas in it. Then I have to pull the choke some to keep from stalling when I pull away from a red light, as it bucks and snorts it's way down the road for a couple blocks and then cools a bit and runs OK until the next stop. Good gas costs more, but I think it's worth it to not have drivability and storage problems. If I use any ethanol gas in my Honda generator, then after a month I have to remove the carb and clean it out before I can start it.

[BILL WILLIAMSON]

Originally Posted by Milton

Now that I am a believer of Model A vapor lock I have to ask why. These cars did not come from the factory with a distributor or carburator heat shield so why the need now? I live inland from San Diego up a three mile 7% grade and in the summer my community is called Hell Cajon, yet I have NEVER experienced a vapor lock in an A. In the thirties these cars were overloaded beyond belief yet made the trip from the dust bowl through the desert to California, how? Methinks there is a cause beyond gasoline, cast iron carbs, etc., retarded timing could do it, lean fuel mixture, what else can cause extreme manifold heat? Anyone?

Yo, Milton,
Betcha' those folks fried a lot of condensors & boiled a lot of carbs, but didn't have the Internet to tell everyone about it. Love that RPU pic, if that dog was BLACK, that could have been my family headin' for ROUTE 66 to go to CALIFORNEY! What adventures we had! Bill W.

[BILL WILLIAMSON]

Just "thinking," a small hose nipple into carb screen access plug, a small nipple sweated high up on the front of the gas tank and connect them with high quality fuel injection hose. This would give an escape route for air bubbles & vapors to get back to the gas tank. (Your thoughts, please!) Bill W.

[Mike V. Florida]

Wow three different posts on the same subject!

I think the common link is heat.

So, why are some cars having the problem and other not?

If you having the problem the problem or not, do you have engine pans installed,
what is your MPG,
what fan do you use,
water or antifreeze,
what grade gas (Reg premium),
how old is your muffer,
do you use one of those inserts in the manifold to seal the exhaust,
what is your average speed,
"Modern" or stock points?

This might give us some common thing to look at.

I don't have the problem, I have engine pans, 18MPG, water, regular with ethenol, 1980's, yes with the insert, 40-45, stock ign.

[1931 flamingo]

Milton n(post 69) and others: In the 30's the engines were "new", most likely no rust/scale formation in the blocks, radiators only a few years old, and people who understood how to set timing correctly, and speeds probably closer to 30-40 mph, AND no ethanol. I, personally, haven't experienced vapor lock, or any other fuel related problems, inside of carb is spotless, running an old in-line metal cannister filter after the elec fuel shut off (late 31 indent. I JMO
Paul in CT

[BILL WILLIAMSON]

Milton,
Glad you don't have "the problem." I haven't had it either.
Have you thought of stopping at the top of your grade for 15 or 20 minutes with gas on & see if it acts up?
We're doing the 100 mile Sierra Scenic Loop soon & I'm going to do several stops to see if mine acts up. Bill W.

[Milton]

Originally Posted by Tom Wesenberg

In the "good old days" they didn't have to fight the bad effects of ethanol.

If I use any ethanol gas in my Honda generator, then after a month I have to remove the carb and clean it out before I can start it.

Do you think, since ethanol is used as an oxygenizer for fuel, that the additional hydrocarbon burning could be increasing the normal operating temperature of the engine?

I understand the generator fuel problem since ethanol has an affinity for water.

[Milton]

Originally Posted by Mike V. Florida

I don't have the problem, I have engine pans, 18MPG, water, regular with ethenol, 1980's, yes with the insert, 40-45, stock ign.

Nor do I, I do not have engine pans, unkown MPG, two blade aluminum fan, 50% antifreeze, regular with ethenol, new glasspack, headers, 50-55+ hard mph, Mallory pointless ign., 5.5 head.

The item that may be saving me is the electric fuel pump that I have installed. Hmmm

[MAG]

Non-believers should not waste their time reading this post.

I concur with Tom. Post #71
"if the temp is over 80 and if I have 10% ethanol crap gas in it. Then I have to pull the choke some to keep from stalling when I pull away from a red light, as it bucks and snorts it's way down the road for a couple blocks and then cools a bit and runs OK until the next stop. "

I and about a dozen or so members tour year-round in an area approx. 250 miles around Austin. There is no ethanol free gas of any octane available in that area. We see a lot of the "vapor lock" problem.

My thoughts are:
The fuel will percolate in the bowl (glass) when the ambient temp. reaches 80 degrees.
The percolation produces "voids" in the fuel supply to the carb.
The voids follow the path of least resistance and that is the fuel line between the bowl and carb. Weight of the fuel in the tank prevents the void from traveling that direction.
Percolation in the carb. does not cause the engine to run rough unless the bowl is nearly empty because the jets are near the bottom. Empty bowl is due to voids in the supply.

We have implemented every suggestion posted here and some we have come up with on our own. None of them have been a FIX. I will list some here:
Fuel - all octane ratings
Additives - MMO, octane booster, diesel fuel, kerosene, StarTron, Sea Foam, and otherss I may have missed. All with variable mixture ratio.
Electric fuel pump with 2lb psi. on Zenith, Zenith B and Tilly carbs. NO Webbers installed.
Fuel line wrapped with rubber, wrapped with head disipating tape, no wrapping.

Current experimentation consists of:
Venting the fuel bowl with 1/16OD capillary tube up to the top center of the firewall. Causes a significant fuel odor in the cab.
Installed a 5/16" fuel line between the bowl and carb. for volume. Thoughts are that with the additional volume provided by the larger diameter, even with the voids, sufficient fuel will be delivered to the carb to keep the engine running properly.

Due to the nature of this problem it is premature to say we have a fix on it. However, on our last tour (about 200 miles) the car equipped as described had no trouble. A couple other cars did.

[Milton]

Originally Posted by BILL WILLIAMSON

Have you thought of stopping at the top of your grade for 15 or 20 minutes with gas on & see if it acts up?

Nope, it has always been my habit to drive across the hill and cool down. Comes from driving before surge tanks were the norm. I never stop at the top hot but, I will give it a whirl when I get my headers back from being coated.