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06-02-2010, 05:26 PM | #21 | |
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Re: For vapor lock nonbelievers
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06-02-2010, 05:36 PM | #22 |
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Re: For vapor lock nonbelievers
Michael, I read somewhere that the early carburetors didn't have a vent and Henry knew this could cause a problem with the float valve feeding fuel. The carburetor's lower half was modified with a vent hole some time in the '30's. How true? I don't know maybe some one else could verify this.
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06-02-2010, 05:38 PM | #23 | |
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Re: For vapor lock nonbelievers
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One more question needs to be answered about heat and gas. When I had the 10% ethanol gas in my tank I parked at the Twin Cities Ford plant on a hot day. A couple hours later I went to leave and the engine started but dies after a few seconds. Gas wouldn't flow to the carb until I removed the line from the carb and established a good flow. A few hours later it did the same thing when I was parked for a couple more hours. So far it's never done that with the good gas, but I'm not sure that I've had it parked for a couple hours on such a hot day either. |
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06-02-2010, 05:45 PM | #24 | |
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Re: For vapor lock nonbelievers
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06-02-2010, 05:51 PM | #25 |
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Re: For vapor lock nonbelievers
I'll have to admit I have several antique motorcycles, and a few antique cars and trucks, and I've never had the dreaded "vapor lock" happen to me. But I've always heard about it, so I can't say it dosen't happen. I'll just keep knockin' on wood.
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06-02-2010, 07:58 PM | #26 |
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Re: For vapor lock nonbelievers
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06-02-2010, 08:51 PM | #27 | |
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Re: For vapor lock nonbelievers
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06-02-2010, 09:56 PM | #28 | |
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Re: For vapor lock nonbelievers
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I don't doubt what you're saying about cracking products--not my area. But, I think that the ethanol and butane effects are two sides of the same coin. The way the ethanol-induced positive deviations from Raoult's Law work to increase the vapor pressure is to drive off the hydrocarbons, such as butane. The resulting increase in air pollution due to excessive hydrocarbons driven off into the air was the major challenge the companies had to overcome before they could bring ethanol enhanced gasoline to market. In other words, the problem is not so much vaporization of ethanol but other hydrocarbons that are unhappy cohabiting with the ethanol. Steve |
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06-02-2010, 10:08 PM | #29 | |
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Re: For vapor lock nonbelievers
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Remember, I saw the same thing in that clear inline fuel filter. I could watch it fill up with vapor and then shut down the flow and kill the engine--true vapor lock. Come to think of it, the only actual Model A vapor locks I've seen have been associated with fuel filters. My own problems are limited to really rough running after long pulls on hot days--textbook vapor lock conditions. I can keep my car running by revving the engine. Steve Last edited by steve s; 06-02-2010 at 10:28 PM. |
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06-02-2010, 10:24 PM | #30 | |
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Re: For vapor lock nonbelievers
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What I think my pictures prove is that fuel vaporization can occur in a Model A. The location of my bubble proves that it does not depend on the carb or any other downstream details. It is a reasonable assumption that under more demanding conditions--like, NOT idling in the driveway with the hood up--actual vapor lock can occur. As I said previously, I do not have actual vapor lock in my car. Under classic, textbook vapor lock conditions (coming to idle after a long pull on a hot day) I get really rough running. I can keep it running by revving the engine. The only actual Model A vapor locks I've personally observed have been associated with a fuel filter. It apparently can trap an impenetrable vapor bubble. Steve |
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06-02-2010, 11:17 PM | #31 |
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Re: For vapor lock nonbelievers
I have never had "vapor lock", I have had condenser lock, and ignition coil lock, condenser lock was cured with an A&L condenser, but I did melt the solder holding the grounding tab on (I ran it for years with it bent to make contact) now they are welded on.
This past Memorial day I tried to induce vapor lock ---- 1/4 tank of winter gas (NJ xtra water reg)bought in december 85+ degree day, walking speed parade --1st gear, idle speed. for added heat--cracked exhaust manifold just after #2 --blowing exhaust directly on the carb bowl It ran fine Later we went for a drive to Ocean City, on the way back got stuck in traffic for 45 min---the drawbridge was too hot and was being watered down to cool it so it would close --still no problem, but I was worried that I would run out of gas, made it home with no problems, no vapor lock. I have never seen any bubbles in my sediment bowl -I use a cast iron sediment bowl. Maybe it is the original late style 2 blade fan --the vibrations from the blades flexing prevent the formation of large fuel blocking bubbles ---or is it the sediment bowl --cannot see any bubbles therefore they do not exist-- |
06-02-2010, 11:34 PM | #32 | |
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Re: For vapor lock nonbelievers
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I am happy for you and everyone else who has never had vapor lock. I'm not sure whether you're joking, but do you really think you could see bubbles in a cast iron bowl? X-ray vision? I was using the plastic fan. Steve |
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06-02-2010, 11:57 PM | #33 |
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Re: For vapor lock nonbelievers
I have toured in the heat when it was so hot the fuel iin the gas line was bubbling like a percolator. I have an inline glass filter and I could see the boiling vapor rise toward the tank. I could hear it boiling in the carburetor bowl. Gasoline and vapor were venting out the bowl vent. I think the 31 indented firewall style valve does not have the necessary trap for the gas to create an embolism like a firewall mounted sediment bowl does. It all vents to the tank. I had hard starting on a hot engine in 115 degree heat up at Crater Lake last year, but once started, it ran fine. The guys with the 29's and 30's were getting vapor lock that was causing stalls in Napa Valley on the first day. We covered their fuel lines, sediment bowls and carburetor bowls with foil backed foam and their trouble stopped.
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06-03-2010, 12:19 AM | #34 |
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Re: For vapor lock nonbelievers
Of course i can not see inside, and also i do not think the the fan blade vibrations have any effect on the fuel system.
Most of the posts about vapor lock mention the glass sediment bowl though. The fuel flow in the cast iron bowl is different than the glass one ---fuel flows directly into the strainer, and perhaps the screen has larger openings in the mesh --I have never compared them for screen mesh counts. Maybe we need a poll ---cast iron --glass, vapor lock yes, no. |
06-03-2010, 12:38 AM | #35 |
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Re: For vapor lock nonbelievers
My friend's and my 29 Tudors are both early 1929's with cast iron bowls and we have both had vapor lock problems on hot days with crap gas.
I do like the theory though "I haven't had the problem, therefore it doesn't exist". I haven't experienced a thrown rod, therefore it doesn't exist. My babbit will live forever! I hope |
06-03-2010, 05:56 AM | #36 | |
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Re: For vapor lock nonbelievers
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Ask a Vietnam veteran.
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06-03-2010, 06:33 AM | #37 | |
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Re: For vapor lock nonbelievers
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Maybe this phenomena occurs to people who alter their fuel system in a way from the stock version(by adding filters or whatever). I really don't know but I still believe you're not going to get true vapor lock in a straight gravity feed fuel delivery system.
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06-03-2010, 06:57 AM | #38 | |
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Re: For vapor lock nonbelievers
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Why is it that with all the model A's running around today only a small percentage have this problem? We all use the same crap fuel, run basically the same cars and drive in the same temperatures. What is it that I'm doing, that this phenomena doesn't happen to me.
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06-03-2010, 07:11 AM | #39 |
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Re: For vapor lock nonbelievers
Dave, What you say about the bowl vent makes sense and I think I read somewhere that was the reason the vent was put in during later production. But not every carb has that hole in the bowl. Mine dosen't and I have been considering putting it in.
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06-03-2010, 09:27 AM | #40 | |
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Re: For vapor lock nonbelievers
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Are you sure your carb doesn't have a bowl vent? I didn't think it was possible for the float control to work unvented. What model carb is it? The vent can be easy to not notice. Here's a photo of one on a B carb that's been plugged so it can be rerouted for air filter use. That brass plug up under the flange part of the lower section is where the hole was. More modern carbs have an internal vent passage connecting the space over the float bowl to the air-intake throat of the carb. Steve |
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