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Say what you want. This doesn't happen until a car has been driven for about 30 minutes in 100 degree heat. The car died shortly thereafter. After I turned on the electric fuel pump I was able to keep the car running.

There is no issue with tuning or air leaks. This doesn't happen when the car is cold.

It is the gas.

Call it vapor lock.

Call it what you want.

Proof:

http://i16.photobucket.com/albums/b37/buick5563/18D79C19-9C25-4A32-A5A7-4AD37D93A25D-475-000000A1E00A6C3B_zps800748a8.mp4

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It should be noted, that this is not my car. I am working on it. Every 322 has this problem, regardless of setup.

The reason I posted is that I changed out the plastic filter that the owner had (with 3/8" rubber lines) to a better filter with the proper 5/16" rubber.

Yes. I AM aware that 1954, 55 or 56 Buicks did not come this way. It is just a good visual as to what happens when "deathanol" meets heat.

No. None of my cars has this filter on it, but the metal lines boil gas just as easily.

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Does it do it if the mechanical pump is eliminated? I ask because after some infrared thermometer readings on my own car this summer, it seems obvious that the gas is super heated in the mechanical pump. Now, I'm not having this problem cause I have a supply of non ethanol gas 2 miles from my home. But I have seen gas boiling in my inline filter in past years. I was wondering if it's worth it to try and build a cooler using an external trans cooler to try and reduce the temp of the gas after the mechanical pump?

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I am running an expensive Carter electric fuel pump (only) on my wagon. I have only had one sputter in the last year with that setup. I don't have a see through filter on that car. Now, of course, it isn't original that way, and I am using an electric wiper on it. In "oil-rich" Texas, we actually do NOT have any ethanol free gas. This is not an issue with any other cars I work on regularly. A friend has a T-Bird, a Chevy wagon and a 60 Electra that don't experience this. The Electra has factory AC that had a vapor return line standard which I believe helps the problem.

I have an inline electric pump on my 55 Special which I use when the sputtering begins.

The video was of a 54 Roadmaster that was a factory AC car that was converted to a Vintage Air trunk unit. (Works well, BTW).

The 55 Special that I am working on is getting all new metal lines, sealed gas tank, rebuilt fuel pump and carb AND a complete sealing of the engine-finished off with a tuneup.

Guess what else?

I am cutting the brand new metal line to add an electric pump, because on these cars...EVERY ONE of the 54-56 Buicks I have ever worked on, has this happen. Regardless of factory air. Aftermarket air. No air. 264. 322.

If they are running ethanol, they boil the gas.

Oh, yeah. This Special (not the Roady in the video) came in with clothes pins on the fuel line.

Ha!

:D

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I should have recorded some audio of my 55 that I drove this morning. After a 35 mile run I let it sit for 15 minutes. After I returned I heard some gurgling at the back of the car (I never feed this car beans)...anyhow I removed the gas cap and apparently heat around the line from the tank to the fuel pump had the gas boiling in the line. My limited research shows that the current crap-for-gas boils at 150*-200*F for summer gas and at 100*-140*F for winter blends. Around here when the outside temps are in the 90's to 100's, there ain't no place on the car that is less than the boiling point of gas.

Willie

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The new gas not only vaporizes at lower temps (thus vapor lock), it also evaporates very quickly. Vented carburetors will go dry quickly, thus causing trouble starting.

A friend called me the other day, had two cars that had been sitting for a couple of years, wasn't getting gas to either one, so he changed fuel pumps, still wasn't getting gas. I told him he wasted money on the fuel pumps, the gas tank was clogged with bad gas. He doubted me, called me today and said I was right, after only two year, both tanks were gummed to the point of no return, and he had to remove them for cleaning.

A friend of mine in the restoration business told me that he couldn't understand the new gas vaporizing so quickly, he put a Mason jar with an inch or so of gas on a shelf, a couple of days later it was gone......

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Has anyone tried installing an electric submersible pump inside the gas tank to hide the pump and solve this problem?

I know a guy who had a Packard Twin Six (known for this problem due to the routing of the fuel line between the manifolds). He installed an electric fuel pump near the tank along with a bypass return line back to the tank to keep cool fuel circulating to the engine. He was the only one who could drive his car in the summer parade at the Packard Homecoming.

Installing a bypass loop keeps the fuel cool by increasing the flow and using the fuel in the tank as a heat sink.

Edited by Mark Shaw (see edit history)
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Vaporizes quickly is right! I have lost count of how many cars (mine and others) that had 4 or 5 gallons of gas in the tank, then the car sat unused for two or three or four months while the engine was out for a rebuild or the transmission was out for some work, or some other reason for it to sit for a few months. When I came back and was ready to run the car again, the gas tank will be completely dry. 4 or 5 gallons will simply evaporate--GONE--in just a few months of non-use, winter or summer.

Pete Phillips, BCA #7338

Leonard, Texas

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Shortly after purchase several years ago, we created a fuel return line of the 1937 Buick 80C Roadmaster Phaeton. We placed a modern fuel filter in line just before the carburetor , and routed the return line to a nipple soldered into the fuel filler neck.

This really helps, especially when touring in areas where you can only get Corn Gas.

We probably should do the same for the 1941 Cadillac which is even more prone to vapor lock as a result of the location of the carburetor.

Both cars have an added electric fuel pump.

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Pete,

I don't think the gas evaporates. It bonds into a genetically modified anaerobic life form called a Monsantite and clings to the inner walls of the tank. Keep the gas cap on tight if you use an attached garage.

Bernie

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Sucessful fuel injection install in a straight-8: http://forums.aaca.org/f118/1950-special-modified-12v-efi-345328.html

Probably easier in a 55 nailhead v-8... and it is getting closer all the time for me.

The excessive volatility not only contributes to vapor lock and 'disappearance', it contributes to gas percolation in the carburetor. I blocked all exhaust in the intake manifold: http://forums.aaca.org/f162/buick-322-intake-exhaust-crossover-363101.html and that helped, but did not eliminate since the underhood temps are still above the boiling point of gasoline.

Willie

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Over the years, several later 1960s and early 1970s cars had fuel filters with "vapor returns" on them, just as some fuel pumps were "two line" pumps. On those particular pumps, there is a drilled orifice inside of the pump which restricts return fuel flow, so the flow bias is to the carb. The size of that orifice IS critical, too, from what we found in the shop in the later pre-FI year. Adding a return line for a "fuel loop" can be a good idea, provided the new line is not routed near any heat-producing parts of the vehicle OR the pavement.

Electromotive now sells a "stealth" in-tank FI pump kit. Uses the orig tank, too. Quite "slick"! But as a FI-level pump, the fuel pressure is too much for a carb'd vehicle, without one heck of a fuel pressure regulator.

As for adding a "fuel cooler" between the pump and the carb, there are many aux coolers which are OEM, now. External trans coolers, power steering coolers, power steering coolers, etc. Add some OEM retainers and you can have a "factory look installation" . . . with salvage yard parts. GM Perf Parts also has an inline electric pump, which looks like a late model fuel filter, except for the two wires coming out of it. I think it was originally a "lift pump" for the 6.2L diesel pickups?

On that vehicle which had the clothespins, did you find any ice cream wrappers, too? That was supposed to be the "other trick" back then.

Just some thoughts,

NTX5467

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The issue of how to adapt older vehicles to modern fuels has been something I've been considering, too. The new self-learning FI systems are great, but I don't know they'd be cost effective at over $2K per kit, per vehicle. Going to an electric pump would certainly "fix" the issue of dried-out mechanical fuel pump diaphrams, but the vanes of an electric pump (unless it was a turbine pump) could corrode internally if the vehicle sits for extended periods of time with ethanol'd fuel in it, then evaporating.

I think the newer Holley "black anodized" carbs might be that way for reasons other than just their aluminum materials and cosmetic reasons, but I've not found that in their literature.

I, too, considered electric fuel pumps to replace mechanical pumps, thereby bypassing the issue of ethanol's drying effect on the pump diaphragm (once exposed, the ethanol-resistant/tolerant rubber can still become brittle if the fuel in the pump evaporates during non-use periods. The vanes in the electric pumps can also corrode from exposure to ethanol fuel, just as other metallic fuel system components can do. So that might indicate the need for a turbine pump rather than a "vane" pump.

The Electromotive Stealth FI fuel pump is a neat installation! Uses the orig tank, too. But it's over 50psi, to run the FI system, making it impractical for a carb'd fuel system . . . unless . . . you used the higher-pressure pump to put enough pressure in the system to raise the boiling point of the fuel, then had one heck of a fuel pressure regulator to get it back to 5-7psi at the carb.

I remember First Born's "budget" FI kit installation, but haven't researched that deal too much, although it certainly has promise for many vehicles. PLUS should cost less than the $2k+ for the self-learning FI kits now on the market.

We OUGHT to be able to overcome this problem, some how! PLUS determine why some models of vehicles seem to be much more prone to such situations, even when they were new as "gas was gas".

Just some thoughts,

NTX5467

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Using an infrared thermometer on a thoroughly warmed 56 this summer, the temp of the fuel line before it reached the mechanical pump was 120* . Obviously a major culprit is the engine heat being blown under the car during use.

The temp of the fuel line after the pump was 170*, and that was on the short 1/4 inch of line that is still exposed right next to the pump itself. An external cooler may reduce the post fuel pump temp, but being just a novice in this engineering stuff, I wonder if it is even appropriate to cool the gas? Since the Buick engineers route exhaust gas under the carb to heat it and make it vaporize better, do you even want cool gas in the carb?

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The one subject I rarely see discussed, when new fuel is debated, is the carburetor itself.

Newer fuel, particularly with ethanol, has less energy available for use. Thus, although there may be 10% less pure gasoline pumped, there is more fuel used overall (I.e. Less miles per gallon), since ethanol has less energy available per gallon.

Over the years, I'd noticed that my Pierce had less get up and go, and like my own body, just attributed it to old age. Then the mechanical fuel pump failed, so I sent it and carb to a fellow who specializes in Pierce Arrow mechanical work.

When rebuilding carb, he re-jetted it for the newer fuel.....whoa....what a difference...the engine has more power, and even sounds healthier, and it's not my imagination.

The point is be that with the new fuel, sometimes a little re-engineering can reap great benefits....

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We need Jon the Carb King to talk about re-jetting. I'm not qualified to figure that one out.

A really smart friend who I respect a lot called me the other day after he saw this thread. He suggested checking fuel pressures at every available location to see where the problem begins. While I couldn't do it on the car I showed the video of, I will do it on one of my cars.

One of the other suggestions has been made in the past (assuming you eliminate the mechanical pump) of running the line up the firewall instead of 4" inches behind the radiator. This would also eliminate (in a 55) at least six feet of 5/16" metal line.

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Vapor lock is always on the suction side of any fuel pump. Any fuel pump will push vapor and fuel. Any modifications to the line between the pump and carburetor is useless. That is why an electric pump near the tank has the best chance of working. On mid 50's Buicks the line between the tank and fuel pump is clamped to the frame crossover under the engine after passing through on the driver side. I have not tried insulating that run of line. I don't know what effect a mechanical pump has on volatile fuel at or in the pump.

My attempt to drive to the Nationals in July was stopped by vapor lock that I have yet to diagnose. The trip was uneventful using only the mechanical pump. After eating lunch in Dalhart, TX, there was some vapor lock (not unexpected) that was corrected by turning on the electric pump (at the tank) for a few minutes. After filling with fresh cold gas in Clayton, NM (elevation ~5000 ft) we headed for Raton, NM (elevation ~8000 ft). After 10 miles running on the mechanical pump vapor lock started and was corrected by turning on the electric pump. That helped for 10 miles and again fuel starvation. The mechanical pump was still attached to the engine block, so I assume it was working; the electric pump could be heard running. We turned around and by the time we got back to Dalhart area (elevation ~4000 ft) it was running fine on only the mechanical pump. Increased elevation lowers the boiling point of any liquid, so that contributed to vapor lock, but the electric pump that had to pull (suction side) only 6" out of a full tank should have worked. Back home I checked the fuel pressure at the carb with only the electric pump (5 psi), with only the mechanical pump (5 psi), with both together (5 psi) all with an empirical flow of an ounce per 5 seconds. I pressurized the line between the tank and carb with 10 psi with no drop in pressure after 30 minutes. I dropped the gas tank and removed the sending unit/fuel pickup and found not leaks there. I replaced the Airtex electric pump with a Carter, and guess what... it still runs great around here! But to test I would have to drive 700 miles and an elevation above 5000 ft! Possibilities: the electric pump failed to pump even though it was running; the new full tank of gas was even more volatile than normal; all crap-for-gas is more volatile than just a few years ago. This car has been over the mountains 6 times previously with the same setup and at really high elevations (Loveland Pass) needed constant electric pump usage.

Recently a friend was driving a 54 in the mountains of New Mexico and was fighting vapor lock problems. After stopping for gas on a cool, rainy evening the car would not start. Apparently after stopping the fuel in the carb boiled in to the intake manifold (percolation) and flooded the engine which usually is only a small problem, but at 7000 ft elevation there was not enough available air to start the engine.

Percolation does not happen only on a stopped engine. On another of my 55's there is surging while driving in slow hot traffic. A friend that was following noted black smoke puffs from the exhaust at that time. crap-for-gas...looks like for these cars it is fuel injection if you want to drive everywhere at all temperatures and elevations.

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I understand elevation affecting gas in a vented carb, and also realize that the slightly lower oxygen content in the air at elevation can affect performance (if I remember correctly from chemistry class, it's the number of molecules, or mole concentration, that matters).

What I do have a hard time understanding is how elevation can affect gasoline in a closed system not vented to atmosphere (gas tank discharge to inlet of carb). I know gas can boil in a fuel pump, but it shouldn't be affected by elevation....

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I understand elevation affecting gas in a vented carb, and also realize that the slightly lower oxygen content in the air at elevation can affect performance (if I remember correctly from chemistry class, it's the number of molecules, or mole concentration, that matters).

What I do have a hard time understanding is how elevation can affect gasoline in a closed system not vented to atmosphere (gas tank discharge to inlet of carb). I know gas can boil in a fuel pump, but it shouldn't be affected by elevation....

The gas tank on these carbureted cars is vented to the atmosphere and any gas that communicates with the gas in the tank (the fuel line from tank to pump) is affected the same.

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Guess that makes sense, absolute atmospheric pressure at 8000 feet is about 75% of what it is at sea level, so the gas from tank to inlet of fuel pump would theoretically be at a lower pressure. That line needs to be protected from heat as much or more than the line from pump to carb....

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Gas tanks have vents just as many carb bowls do. In the case of the tank, if there's NO vent, the fuel pump's suction will try to collapse the tank if it is not vented (either via the fuel filler cap, an under-car vent, vented through the carbon canister for emissions-controlled vehicles, or otherwise.

One rule of thumb for carb jetting vs elevation is .001" smaller per 1000 ft of elevation above sea level. In some cases, you can advance the base timing a little to achieve the same "re-jetting" effect for temporary trips to higher elevations. Why? The "thinner" the air/fuel charge, the more "lead" it takes to fire it off (which is why vacuum advances help driveability and fuel economy so much. Using the same jetting at 10K feet will result in an over-rich mixture, IF the jetting was calibrated for at-or-near sea level.

The "stoich" mixture for E10 is 14.2, E15 is about 13.7, whereas for E0 is 14.8. Re-calibration seems to affect the older vehicles a little more than newer vehicles, although we would have suspected those other vehicles would have been calibrated toward the rich side of things to start with. Only thing is that once the carb is calibrated for the "new fuels", it can be a little rich should "normal" fuels be used in the future (either from a drum or in a part of the nation where E10 is not used). So, whatever works for you!

In the pressure/vacuum/elevation situation, might the fuel pressure/vacuum situation change a little with a larger fuel supply line in the tank AND under the car? Or might the larger line result in slower "speed" of the fuel going through the lines (same pressure, greater flow, less "vacuum" behind the pump)? But might the resultant slower "speed" of the fuel in the lines, from the larger diameter fuel lines, allow them to absorb more heat from the roadway under the car? Might the smaller line accumulate more frictional heat from its higher flow speed through the lines? Unless the under-car plumbing is completely insulated and the fuel tank is heat-shielded, there will always be heat absorption by those parts of the fuel supply line.

One of the first "factions" of the fuel chemistry to evaporate would most probably be those related to ethanol and octane enhancement. Gasoline from which the ethanol has been "washed" (added water to cause phase separation, then that gunk removed from the mixture) has been said to be about three octane numbers lower than the original fuel blend. This could result in fuels of too low of an octane number to use in some engines, unless some non-alcohol octane booster is added.

Fuel percolation was an issue on some vehicles well before we got the more recent fuel blends with ethanol. THIS percolation was due to high underhood temperatures (with the engine stopped) than from fuel blends, though.

A fuel "after-cooler" (post engine-driven pump) could result in a cooler fuel bowl temp (the reason for the Carter ThermoQuad's different float bowl material and the reputed 20 degrees cooler fuel temp) and more consistent metering activities, but also understand that once in the intake manifold, the charge temp will decrease again (sometimes needing the exh crossover heat to help with cooler temps driveability). Some emissions systems have a "charge air temp" sensor for this reason.

Previously, when I mentioned "two line pump", that should have been "three line pump", where the third line is the smaller diameter return line to the tank, rather than using a vapor separator/filter between the pump and carb.

Fuel system design can be a tricky situation!

Just some thoughts,

NTX5467

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Willie - I would concur with virtually your entire post 23 except "Any modifications to the line between the pump and carburetor is useless".

One of the easy ways to add a return line to a vehicle that did not have one originally is to insert a 3 line fuel filter (readily available at most FLAPS) right at the carburetor. The carb gets first chance at the fuel because of the larger filter orifice, and the remainder of the fuel is pumped back to the tank through the return line. This allows the fuel pump to pump at close to rated capacity thus the fuel does not stay in the line long enough to cause vapor lock on the suction side of the pump.

The cooler fuel delivered to the carburetor will MARGINALLY improve power and economy (10 degrees F cooler fuel is good for 1 percent improvement).

Jon.

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one more comment, on early cars (let's say pre WW2 for the sake of this discussion), if you install an electric fuel pump, make sure it's very low pressure..2 or 3 pounds max....higher than that you'll easily overcome the float/needle valve on an original carb.....also make sure there's a positive shut off for electric pump....I've been there, and it's no fun trying to put out an engine fire and realizing the electric pump is still feeding the fire.....

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If possible, fixed power for an electric fuel pump should come from an oil pressure switch. If power is simply through the ignition switch, the power might still be on in case of an accident.

A temporary (push button) switch is OK to prime the pump.

Jon.

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Willie - I would concur with virtually your entire post 23 except "Any modifications to the line between the pump and carburetor is useless".

One of the easy ways to add a return line to a vehicle that did not have one originally is to insert a 3 line fuel filter (readily available at most FLAPS) right at the carburetor. The carb gets first chance at the fuel because of the larger filter orifice, and the remainder of the fuel is pumped back to the tank through the return line. This allows the fuel pump to pump at close to rated capacity thus the fuel does not stay in the line long enough to cause vapor lock on the suction side of the pump.

The cooler fuel delivered to the carburetor will MARGINALLY improve power and economy (10 degrees F cooler fuel is good for 1 percent improvement).

Jon.

Thanks, Jon

I thought of the return line, but before this trip to the mountains, I though the problem was solved. Also, I was waiting on someone with first hand experience on a 55 with that set up.

Also, while I have you here, is there anything to do to an otherwise perfectly functioning WCFB to reduce the fuel percolation on the available fuel?

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If there is not already one there, a thick spacer made from a heat insulating material can be used under the carb to reduce heat transfer from the engine.

Something like this for example: http://www.ebay.com/itm/Carter-WCFB-Phenolic-Carburetor-Insulator-Spacer-4-Barrel-Heat-Soak-Riser-Kit-/261556767976?_trksid=p2054897.l4275

Edited by Wheelnut (see edit history)
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If there is not already one there, a thick spacer made from a heat insulating material can be used under the carb to reduce heat transfer from the engine.

Something like this for example: http://www.ebay.com/itm/Carter-WCFB-Phenolic-Carburetor-Insulator-Spacer-4-Barrel-Heat-Soak-Riser-Kit-/261556767976?_trksid=p2054897.l4275

Might work in some cases. There is not enough room on a 55 to raise the carb without jamming the air cleaner into the hood. On mine, I already blocked off all exhaust to the intake manifold, so the carb is not over heated by exhaust....and it still percolates!

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Thanks, Jon

I thought of the return line, but before this trip to the mountains, I though the problem was solved. Also, I was waiting on someone with first hand experience on a 55 with that set up.

Also, while I have you here, is there anything to do to an otherwise perfectly functioning WCFB to reduce the fuel percolation on the available fuel?

Willie - nothing of which I am aware will solve the issue.

However, the return line will minimize the issue. Why? Once the engine shuts off, the inlet valve in the fuel pump closes, preventing fuel from returning to the tank. The engine heat then builds pressure in the fuel line, and dumps additional fuel into the carburetor which will also percolate or leak out beside the throttle shafts. The return line relieves the pressure back into the tank, so a few tablespoons of fuel don't get dumped into the carb to percolate.

Jon.

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Willie - nothing of which I am aware will solve the issue.

However, the return line will minimize the issue. Why? Once the engine shuts off, the inlet valve in the fuel pump closes, preventing fuel from returning to the tank. The engine heat then builds pressure in the fuel line, and dumps additional fuel into the carburetor which will also percolate or leak out beside the throttle shafts. The return line relieves the pressure back into the tank, so a few tablespoons of fuel don't get dumped into the carb to percolate.

Jon.

That sounds plausible Jon... but I doubt it. The fuel in the line has probably already gotten pretty hot by that point and isn't going to get much hotter after shut down than it already is. The fuel in the line would not be significantly cooler while running, because the flow is not great enough to make much of a difference. Besides that, the float valve should still shut off any marginal pressure increase. The most probable cause of heat soak problems after shutdown will simply be the boiling of the fuel already in the carb float bowl. After shutdown there is no longer any cooling effect from airflow through the carb, so it's going to heat up dramatically and rapidly. Edited by Wheelnut (see edit history)
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I used to have hard starting problems on my MGB roadster after shutting it down on hot days. I had just converted it to the earlier dual carb setup but didn't have the heat shield that goes between the carbs and the engine. The heat shield is just a flattish piece of sheetmetal. I added a home-made heat shield made from a thin piece of shiny aluminum and that cured the problem. It worked by just blocking the radiant heat from the engine and exhaust manifold.

A simple reflective heat insulator sleeve slipped over the fuel line will do a lot to keep it cooler. A reflective heat shield under the base of the carb, combined with the phenolic carb spacer, will reduce carb temperatures significantly. Not very original looking, but effectve.

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That sounds plausible Jon... but I doubt it. The fuel in the line has probably already gotten pretty hot by that point and isn't going to get much hotter after shut down than it already is. The fuel in the line would not be significantly cooler while running, because the flow is not great enough to make much of a difference. Besides that, the float valve should still shut off any marginal pressure increase. The most probable cause of heat soak problems after shutdown will simply be the boiling of the fuel already in the carb float bowl. After shutdown there is no longer any cooling effect from airflow through the carb, so it's going to heat up dramatically and rapidly.

We have been suggesting this patch for maybe 25 years. We have heard back from literally hundreds of customer after the patch was installed. Believe me, it DOES work!

This link to our website troubleshooting section explains it better:

http://www.thecarburetorshop.com/Troubleshooting.htm#Fuelleak

Jon.

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