Vapor lock and percolation

[Rosiesdad]

Hi all. My '50 Buick has been having some fuel supply issues. It has a Carter 2 barrel carb . Historicly the car ran well after I fixed the stuck heat riser and rebuilt the carb. I found a 6v fuel pump installed near the tank, and the fuel level in the glass bowl filter next to the carb was normally almost full to the top of the bowl even without the pump turned on so I normally never used the electric pump.

The car spent 8 months in the body/paint shop and when I got it all back together I began having problems I never noticed before.

1. When parking the car I found it often wouldn't restart. It appears the fuel percolates into the intake manifold and floods the engine. With some effort I can get it going after using some starting fluid.

2. When idling for a long period the glass filter bowl will empty. Turning on the fuel pump will not fill the bowl until I open a fitting to bleed the vapor from the filter bowl. Then I can try and restart.

This is a problem even on slightly warm days. The only thing I had done was I put a new electric fuel pump on to replace the intermittently working one and I checked and cleaned out the glass fuel filter bowl near the carb.

Now I have problems constantly. Either percolation or vapor lock or both at the same time!

The engine appears to operate in the usual heat range. Is there any way to prevent the fuel from percolating into the intake? I am considering removing the glass bowl filter and putting in a tee to return fuel to the tank while running the electric pump constantly. I am hoping the carb will percolate back to the gas tank but not sure about that. Also will install a better carb base insulator. Maybe hotter heat range plugs to help it fire when flooded? I just don't know why this is suddenly a problem. Gas has been changed out several times.

Any insight is appreciated!

Phil

[Aaron65]

Hey Phil...

First, hotter plugs won't help, and they could damage your engine by acting as "glow plugs" at higher speeds. They don't fire hotter, they just retain heat to keep them from fouling, and I don't think that's for just on start up, more for an engine that fouls them while running. My '53 has always started hard hot, largely due to the non-carburetor friendly gas we now have, but also due to the fact that there's a 600* exhaust manifold underneath it. I maintain a mechanical fuel pump, but I also have a 7/16" spacer from Bob's Automobilia, and I made a fuel return. By using one of those bypass fuel filters, I ran a return line to the filler neck, but I think the tank would be better if you could make it happen. I also stretched the exhaust valve body spring so it was always closed. I don't drive it in freezing weather, so I just have to put up with it being a little bit stubborn for the first half mile or so most of the time...basically I can't get on the gas quick or it will want to stall for a bit. Finally, there are two schools of thought for starting the engine hot. The first is to just touch the starter and not push down far on the gas pedal at all. I found that mine personally likes the owner's manual advice for a flooded engine...pushed and held all the way to the floor (no pumping). With the fuel bypass, mine now starts hot most of the time within a couple of seconds. Even so, I still get a raw fuel smell and a little black smoke most of the time. I think it's just the nature of the beast, but I haven't tried an electric fuel pump or anything either. Good luck!

[rons49]

Phil I mostly agree with Aaron. The gas on some Carters percolates after the engine is shut off until the engine cools. The percolation overflows the main jet and drips down into the manifold. Many times this is caused by a thing called anti -percolation valve that looks like a saxophone key. There is a correct adjustment to these A-P valves. If they stay closed after shut down, the excess gas floods over since the venting is blocked. Also, a thicker gasket ( preferably phenolic ones) helps avoid heat in the carb. Sometimes the float level is a bit too high due to the lighter fuels of the day. I did not solve the issue with a return line, but in theory it should work ala Chrysler & Amc. That is an envolved process requiring possible drilling a hole in the filler neck of the gas tank, & a restrictor( about .030) inline is necessary to maintain fuel pump pressure. Doesn't the Buick start by holding the pedal to the floor? That should clear the flooding in a few seconds. An electric pump is a good idea, but probably won't help on part warm restarts. Keeping the fuel lines cool with insulation is a help. Buy Mylar from Jegs online. I'm not in agreement on the Heat Riser(Exhaust valve?). By just disconnecting l, I the spring, the H-R valve defaults to open position and this is the normal warmed position. If it remains closed heat diverts to the intake and may vapor lock faster & stress the valves. At least that what happens on my 50 Caddy. Ron

[NTX5467]

With the orientation that carb percolation is due to the nature of the beast of an inline engine (with the intake manifold above the exhaust manifold), then EVERY inline 6 cylinder would have had similar issues as the inline 8 cylinders, it would seem.

Right now, everybody's looking at "engine" things (fuel line insulation, carb base gasket insulators, etc.) when it probably might be good to look at air flow across the engine to better keep everything cooled as the engine runs. This would probably mean a fan with more blades and more "pitch" to the blades, to start with. Ensuring the radiator is internally clean would be necessary, too, not going by what it looks like through the filler neck. And, of course, as has been discussed in here a few times over the past 5 years or so, doing a FULL flush of the engine block by removing the "freeze plugs" and getting ALL of the combined accumulated gunk and rust out of the BACK end of the water jacket (where it'll usually accumulate). It's certainly messy to do, but the only real way to ensure the cooling system is operating at peak efficiency.

Where we didn't have many issues with hot restarts (on the 6 cylinder GMC pickups we were driving back then, with the "foot-feed starter", too), with the newer "easier to evaporate" gasolines we now have, "hot soak" restarts can be more of an issue. I don't know that tweaking the float levels might offer enough benefit, as it's heat being absorbed by the carburetor body that causes the percolation situation. Using the phenolic spacer/insulator can certainly help matters, I suspect. It might also be possible to configure/fabricate a thin aluminum plate heat shield to go on top of the phenolic insulator and then put a normal thin carburetor gasket between the carb and the shield . . . ala the GM/Holley-sourced similar item on early '70s 4bbl Chevy V-8s, or the aftermarket Mr. Gasket "insulator stack" gaskets. Might need some longer carb studs/bolts, though.

Another thing would be to ensure the ignition system is doing all it can do! I'm not sure which spark plugs those engines might use, but I suspect they are "non-extended gap" plugs, where the plug gap is just above the end of the spark plug. This is not too good to get the flame kernel out in the combustion chamber area, but it was common for how things were done back then. If there might be a good heat range with an extended tip plug, that might help starting. Then, when you gap the plugs, take a pair of pliers and gently rotate the ground electrode such that 1/2 of the center electrode is "exposed". This will allow the flame kernel to better expand into the combustion chamber AND might also aid starting. Another way would be to "J-gap" the plugs, which would require taking a pair of diagonal cutters (works faster than filing them down, as I used to do) and snipping the ground electrode such that (again) about 1/2 of the center electrode is exposed. It might be necessary to use the point file to dress the ground electrode to remove sharp or deformed edges from it, but ensuring the electrode is square and proper, at the proper gap.

Vapor lock will happen as heat radiates up from the pavement and heats the fuel line enough for the enclosed gasoline to "evaporate" before it gets to the carb. This is where the electric fuel pump comes in. Many of our associates with '55 Buicks have an auxiliary electric pump they'll switch on if they're going to be in slower-moving traffic in warm(er) weather.

Chrysler did use a vapor separator/fuel filter on some of their V-8s along about 1970 or 1971. Other makes have used variations of them over the years. In that time frame, many carbs came with "hot idle compensator" valves (usually 4bbl Holleys, where this "valve" was hidden under a small side plate on the carb). It would open during "hot idle" situations such that the idle mixture would remain "in specs", but also might allow "venting" to happen, too. Most carbs back then had "bowl vents" which were open at idle and lower rpm levels, too . . . later to be vented to the carbon canister on later models.

Various later 1960-middle 1980 GM models used a "three line" fuel pump, with the third (smaller) line being a "return line" from the fuel pump to the fuel tank, which also had a drilled orifice restriction in it. The restriction is there to force the bulk of the fuel to the carb, though, which is different than the Chrysler vapor separator/filter mechanism.

I'm not sure about the "saxophone key" valve which was mentioned, but it sounds like the "hot idle compensator valve" with a different function. But if there's an adjustment for it, it might need to be altered a little due to the quicker-evaporating fuels we now have.

I do know that if there's enough air flow across the engine as it operates, the underhood area will be cooler. Either a booster fan in the front or a "more blades" fan for the front of the water pump. Make sure, too, that the radiator's fins are completely clear of debris or blockages!

Just some thoughts,

Happy Holidays!

NTX5467

[Curti]

the spring, the H-R valve defaults to open position and this is the normal warmed position.

Is this true? I would think the 'default' position would be closed to divert the exhaust to the base of the carb on a cold start up. Then as the bi-metallic spring unwinds the flapper valve assumes a horizontal plane and the exhaust is able to flow streight through.

It is easy to install a heat-riser spring in backwards.

[Joseph P. Indusi]

My understanding is that the thermostatic spring relaxes with heat and no longer holds the valve in the "cold" position that forces some exhaust gases through the plenum of the intake manifold just under the carburetor to help speed up the warmup. When hot, the spring allows the counterweight to move down by gratiational force and the flapper then directs the exhaust gasses directly out to the exhaust pipe.

Check anything that you changed from before when the car started easily to the problem you have now. I would check the insualtor under the carb and be sure the carburetor bolts fastening it to the mainfold are snug. On my 53 Special, I slowly depress the accelerator pedal until the starter engages and the engine starts, especailly when hot. Check carefully all the steps and settings involved in the carburetor rebuilding.

Good Luck.

Joe, BCA 33493

[Curti]

I thought the spring relaxed myself, until I heated one up on my bench. Possibly they differ from car to car. Chevrolet 1937-1965 expands

[rons49]

The hot spring does expand, and thereby releasing tension . There is tension on a "cold" spring which overcomes the weight. When hot, the tension releases, and the weight pulls the valve open. By disconnecting the spring off the stud on a cold engine, the spring tension is removed and the weight performs the same action as when Hot and connected. I doubt this is Phils problem. Unless the heat riser stays closed due to rust or ? Phil, does your car have the Carter WCD 725s. These don't have anti -perc valves. I have a 742s on my 50 Caddy. No problems ever. Try this. I know it's not SOP but,... do not push the pedal to the floor , don't touch it at all. Crank the engine for about 5 seconds. Then gently push the gas pedal 1/3 down and re crank. I saw this on line due to the modern fuel this was suggested. However with the carb/starter, that is out.

[NTX5467]

I would think the slow accel pedal depression would be a good procedure on a hot engine, or one which was hot and then sat for a while. This can result in more of a dribble from the accel pump jets rather than a GUSH (if the accel pedal is depressed quickly), which can let the gas from the jets partially evaporate from the hot manifold. With a quicker depression, the "GUSH" will then puddle in the manifold runners and not fully evaporate before the engine is cranked.

On the heat riser spring, the tension should close it at cooler ambient temperatures. If the outside ambient temperature is not very high, then it can remain somewhat closed even as the engine heats up to operating temp internally. But if it's still working and free, higher rpm exhaust flow should allow it to open more, as needed. Most of the ones I've seen over the years were usually stuck about mid-travel, which might not be so bad as "full closed".

We I was driving our '66 Chrysler all of the time, I had noticed that its heat riser valve was about 40% open, and firmly stuck there. When we'd take it in for a tune-up, they'd free it up, but it ended up back where it was, so we just left it there. In later years, we put in an OEM Chrysler repair kit. That model used bronze bushings for the shaft to rotate in, which were put into the shaft holes in the manifold. When the new kit was installed, it was as "tight" as the old valve. When I commented on that, that "we'd be back where we were in a few months . . . ", (before the manifold was reinstalled on the engine), the service manager removed the valve from the manifold and then reamed the bushings so the shaft would freely fit into them and turn freely. THEN, it worked correctly and kept working for quite some time. When it did stick, a little of the correct solvent helped free it up again.

Perhaps something of the same nature might work on the older inline engines, too? I never knew there were bronze bushings in there until we put the new kit in. But in later years, it became apparent that there should usually be some "replaceable wear interface material" to prevent a part being ruined due to wear.

Just some thoughts,

NTX5467

Edited December 27, 2012 by NTX5467 (see edit history)

[Rosiesdad]

Thanks guys,

I went for a nice drive the other day without problem. She started hard since it had been a while since I ran her. I didn't want to flood, so I usually push the accelerator to just where the starter engages. I find that I can run the 9 psi fuel pump without flooding so plan on leaving that on all the time if I can. I will get a new carb insulator and also wrap the fuel lines. Maybe use a smaller inline fuel filter rather than the big glass bowl.

Will check the heat riser to make sure it is still hammered where I left it. We don't really need it here in NorCal. Maybe a little lower float bowl level will help stop percolation into the intake.

I guess the trick set-up going forward with our crappy fuel is to circulate fuel back to the tank and get a carb with an anti-percolation valve and I'm IN!

Hmmmmm..... Do those cool dual carb setups have anti-perc carbs????

Thanks,

Phil

[rons49]

Thanks guys,

I went for a nice drive the other day without problem. She started hard since it had been a while since I ran her. I didn't want to flood, so I usually push the accelerator to just where the starter engages. I find that I can run the 9 psi fuel pump without flooding so plan on leaving that on all the time if I can. I will get a new carb insulator and also wrap the fuel lines. Maybe use a smaller inline fuel filter rather than the big glass bowl.

Will check the heat riser to make sure it is still hammered where I left it. We don't really need it here in NorCal. Maybe a little lower float bowl level will help stop percolation into the intake.

I guess the trick set-up going forward with our crappy fuel is to circulate fuel back to the tank and get a carb with an anti-percolation valve and I'm IN!

Hmmmmm..... Do those cool dual carb setups have anti-perc carbs????

Thanks,

Phil

Phil, the Carter WA-1, WE and WAs have 'em. What brand and model electric fuel pump are you using? 9psi is high and may flood at idle or if it is a free-flow type, gas will be restricted when the EP is off, requiring you to run the EP all the time. If the psi is actually 9 I would advise a fuel regulator, and not one of those "dial in" type.

[Owen_Dyneto]

I agree completely with Rons49, 9 psi fuel pressure is WAY TOO MUCH and can easily overwhelm the needle and seat which was designed to operate at pressures usually not exceeding 4 to 4-1/2 psi.

[Guest chevy_dude97]

I agree completely with Rons49, 9 psi fuel pressure is WAY TOO MUCH and can easily overwhelm the needle and seat which was designed to operate at pressures usually not exceeding 4 to 4-1/2 psi.

I would measure pressure @ the carb. If its installed all the way back at the tank it is most likely dropping pressure by the time it gets to the carb.

[Rosiesdad]

My plan is to run as high a pressure as I can to prevent vapor bubbles in line before the carb. The pump is a Airtex E 8011 with a max PSI of 8.

I idled a long time in the driveway without it loading up. I had opened the float bowl inspection hole and held the floats up but gas kept coming out over the threads..... I though it was forcing past the bowl seat but it stills idles fine so not sure about that test. If I install a regular inline filter in place of the glass bowl it might drop the pressure a bit maybe. The main problem is percolation flooding. Looks like I should put in a manual starter button so I can crank it without gushing more gas in each start attempt due to the accelerator linked start switch.

[NTX5467]

To really determine if the engine is running "rich", you need to check the color of the spark plugs. By the time the engine loads up, falters, and then dies from over-rich mixtures, the plugs will be highly carboned to the extent that the spark will not jump between the electrodes. Just because it will idle for a while, seemingly normally, does not mean the mixture is not too rich.

8psi IS more than the carbs were designed to handle--period. IF your pump is actually putting out 8psi, which is why an inline gauge, even if installed temporarily, is needed to see where things are. It could well be that the pump can handle up to 8psi into a particular size fuel line, but it could ALSO be that the pump comes factory-delivered at the 5.5-6.0psi setting which carburetors WILL handle. Plus, such pressure readings are usually obtained with a specified restriction they are running against AND with a related gallons/hour notation. Gallons/hour is needed as an engine usually requires about .5gal/hour per horsepower it produces at WOT, while also maintaining enough pressure at the same time.

Unless you pressurize the complete fuel system, even to 6psi, including the fuel tank, then the pressurization idea to increase the fuel's boiling point can be sub-optimal. I suspect it would be better to first ensure the fuel tank is either "natural silver" or install a heat shield on it to insulate it from heat radiated from the pavement. Then further heat-shield the fuel line under the car, for the same reason. Ensure the fuel tank is properly vented to maintain atmospheric pressure inside of it, rather than it "pulling a vacuum" (of any level) as the fuel pump removes gasoline from it.

Once at the engine, make sure that all "natural" fuel lines are buffed shiney with some red Scotchbrite, for better heat reflectivity. Also ensure they are not physically touching any heat-producing area of the engine.

Changing to an inline fuel filter, in the orientation that it might change things, might not really be a benefit. Certainly, the rubber lines would insulate it from the metal lines, but it'll still be subject to ambient underhood heat just as the glass bowl was. If the desire is to add an inline fuel restriction to help with the percolation, that would just increase the load on the fuel pump without much pressure change. Eventually, as the needle and seat work in their regulation function, the pressure between the carb and the new filter would be the same as the pressure at the new filter's entry point. Kind of like using a collection/retention pool for rain runoff before it hits the creeks . . . it all gets there eventually, just not as fast as it otherwise would.

Remember, "percolation" happens AFTER the engine stops. Vapor Lock happens BOTH after the engine stops AND while the vehicle is in operation. Percolation is due to engine/underhood heat. Vapor Lock happens "under the car", behind the engine. I

f you suddenly pressurize the system, after a "heat soak", the suspected bubbles will need somewhere to go, so THAT's when you'll need a fuel return line to the tank, from a point between the mechanical pump and the carb. Seems like a LOT of additional re-engineering of a stock vehicle to fix something which some more basic things might better address! Plus, as soon as the bubbling fuel hits the glass bowl or carb float bowl, they'll be vented anyway, it seems.

Percolation happens after engine compartment heat rises to a certain level after the engine stops, when underhood air circulation ALSO stops. Seems like it would be a big bunch better to add a "pusher" electric auxiliary engine cooling fan in front of the radiator, to run a short time after the engine stops, to help things cool down sooner than to orchestrate a LOT of engineering changes (which are more costly) to attempt to achieve the same result. Even making a conscious effort to park the vehicle, nosed into the wind, would very possibly help things.

The ultimate fix would be to get a new stainless steel fuel tank set up for fuel injection, use a high pressure in-tank fuel pump, convert the car to fuel injection (seems like Holley has some 2bbl conversion kits, but for 12V?), and then that'll give you a fully pressurized fuel system . . . all of the time. If the installation was well-finessed, then only some people who knew what they were looking at would know what had been done. But then, too, so much for some national level car show judging classes.

Changing the float level of the carb will most probably NOT have a significant affect, I suspect. With less fuel in the bowl, if even an ounce, the quicker it will reach "percolation" temperature than if there is more fuel in the bowl as there is less fuel there to absorb the heat. More fuel wlll require MORE total heat before it gets to that same temperature point of boiling. IF you're trying to fight "fuel expansion as it gets hotter", then a slightly lower level might help, but if it's the "boil over" you're trying to stop, the lower level might only make it worse. Kind of a no-win situation, it seems. Remember, too, that the original float level was most probably fine-tuned to operate well, back then, in places of the country which were consistently HOT, like Arizona (where almost every car company had a test/proving grounds back then) and higher altitudes like Colorado. Only difference between now and then is the increased volatility of the fuels for emissions purposes, even BEFORE the E10+ ethanol came into the picture.

I suspect you've also checked the radiator to see if it might have become partially blocked with "body shop debris"? What's the operating temp as you drive it ANd under what conditions? How long since the cooling system was fully flushed and ALL of the block freeze plugs replaced?

If you don't have one, I suggest you get a non-contact infra-red "heat gun" thermometer. With that, you can reasonably accurately check the various underhood temperatures of engine parts and fuel system parts as the engine runs and also a certain time after you turn off the engine. In this way, you might better determine where "the heat" is coming from and in what magnitude/intensity. It might be possible to find the stated boiling point of gasoline (at sea level) in some of the gasoline manufacturer's MSDS data? You can also use it to check the various temperatures in the radiator (entry, exit, and in-between). IF you're effectively going to "attack" this heat issue, you need to know WHERE it's coming from, in what intensity, and why . . . otherwise you can "chunk parts/things at it" and not have a really good result . . . other than the "Look what I did!" dialogue.

Respectfully,

NTX5467

[rons49]

NTX Very professionally and well stated. I spent years ( on & off) trying to find eliminate the "fuel starvation" issue with my Hornet, even going as far as the fuel return line back to the filler neck. In the last few years, I seam to have solved it. Insulation ( mylar) on fuel lines to the mech pump, which is set up for 5 PSI. Arizona roads are frying pans in the summer. Rerouting of the fuel pump to carb steel line away from the exhaust manifold, thereby increasing the distance from 3 inches to 8", then placing a length of easily removable mylar over the steel line. The carb spacers( gaskets) were only two deep above and below the heat shield. Replaced those with phenolic spacers as thick as the studs would permit. The car already has an AC/Delco 8011 electric pump as a primer, although I rarely need even it for that. Still one quirk, some times I have to hold the pedal to the floor and crank for a 4 seconds on a partly hot restart.Next summer, I have a couple of procedures that I want to try to address that.

[Curti]

Rerouting of the fuel pump to carb steel line away from the exhaust manifold, thereby increasing the distance from 3 inches to 8", then placing a length of easily removable mylar over the steel line.

I was told by an old timer that copper line disipates the heat better. An extrapalation of that is the reason that welding torches have copper tips. Even though copper melts at a lower temp than steel it dosn't because of the heat transfer properties.

[olply]

I drive a 1938 Plymouth and have had the same flooding problems.  I tried spacers, relocating and insulating the fuel line, and adding fuel oil to the gas.  Some of these ideas helped slightly, but none of them cured the flooding problem caused by fuel percolation in the carb.  My cure is to install a fuel cutoff valve just in front of the carburetor and to cut off the fuel just prior to turning off the engine.  At idle it will run for about 70 seconds, or less if you give it more gas. Since I am still running 6 volts, my cutoff valve is manually controlled with a cable run to just under the dash.  This system works quite well since fuel can't percolate if it is not present.

[jp928]

Apart from lowering the EP pressure back to what the carb expects, I would also check for signs of deposits settling out of the gas while it was parked up for months. If you have anything on the needle and seat it would not seal properly, and deposits in the lines wont help either. With a car with a fuel return line that had this problem I have had good results from loading the tank with oil like Berryman's or Marvel Mystery oil, and letting the pump run for an hour or so (while you are close by!).

Vapour locks usually occur when you have either hot fuel, and/or a sucking pump above the tank. The action of sucking lowers the pressure above the fuel, which tends to lower its boiling point and start it vaporizing. When I was you we had  a car that did this, and found that painting the botoom of the tank that was exposed to road heat help to keep the fuel cooler, and reduced vapour locks. A pump located near the bottom level of the tank should never get any vapour problems. 

jp 26 Rover 9

[JWLawrence]

Vapor lock takes place in the non-pressurized portion(s) of the system. That is on the suction side of the fuel pump and in the bowl of the carburetor. Electric fuel pumps are usually mounted as close to the gas tank so as to have as much of the line pressurized when the pump is on. Insulating the fuel pump helps. A shield between the pump and the exhaust manifold is one recommendation. An insulating gasket between the pump and block helps. Some manufactures went farther with insulating sleeves and washers for the mounting bolts. Wrapping the fuel line from the pump to the carb is probably not going to help much. A heat shield between the carb and manifolds when coupled with an insulation block between the carb and intake manifold should provide a good benefit. Also, assure the anti-perc valve and/or carb bowl vent are working properly. Of course a properly functioning heat riser valve is important. A more elaborate fix of providing a fuel re-circulation line from the pump back to the tank has received good reports. Finally, make sure the gas cap is a vented type. Some have reported good results using a 5% mixture of diesel or some Marvel Mystery Oil added when refueling. I had good results using the diesel mixture. Hope this helps.

 

(o[]o)

[carbking]

Lots of good suggestions in this thread.

 

A few random thoughts:

 

(1) You may have multiple problems!

(2) As stated by others, fuel pressure of 8 psi is TOO MUCH! A fuel pressure gauge at the carburetor to test ACTUAL pressure.

(3) The WCD does NOT have the anti-percolation valves. These were used on earlier Carter carbs, and were troublesome as exact adjustment was desirable, plus the valves stuck with age creating idle issues. The WCD has 2 permanently open bowl vents which vent bowl vapors to the atmosphere.

(4) The fuel bowl in the fuel filter acts as an expansion tank, collecting vapors from percolation of fuel (even pressurized) in the fuel line, keeping a more constant pressure on the carburetor fuel valve. These vapors WILL run through the fuel line into the carburetor bowl when the carburetor float is calling for fuel, and then exit the bowl into the atmosphere via the bowl vents. It is not unusual for the fuel filter bowl to not be full during hot weather.

(5) The probable cause of hard hot starting is heat soak, rather than vapor lock: http://www.thecarburetorshop.com/Troubleshooting.htm#Hardstarthot

(6) A phenolic spacer between the carb and manifold MAY (or may not) help the heat soak issue. Generally, the starting method described in the link works. You may have to get your toe under the footfeed to activate the starter switch on your Buick.

(7) Except for filling an empty carburetor at start up time, a mechanical fuel pump is desirable ON NON-RACE VEHICLES to an electric pump. WHY? Because the electric pump is constant flow, constant pressure; whereas the mechanical pump is driven by the camshaft (generally) and therefore has variable flow and pressure dependant on the needs of the engine.

(8) Fuel tanks MUST be vented. Some (I don't know about your Buick) were vented through the fuel cap. Replacing a vented fuel cap with a non-vented cap is a sure method of heartache!

(9) A fuel return line generally helps heat soak. The shut-off valve mentioned in an above post may work as well, but it might also increase pressure on the line to the point where the fuel valve or carburetor float could be damaged when the valve is opened.

(10) Using higher than required octane will generally make these issues WORSE! http://www.thecarburetorshop.com/Octane.htm

(11) If you do install a pressure regulator, resist the urge to buy one of the $29.95 dial types from the FLAPS. These are quite useful if you have a rabbit issue in your garden, and a strong right (or left) arm!  They also may be used as paper weights. Go to a speed shop, and buy a good (read expensive) regulator with an adjustable bypass.

 

Many of these items have already been mentioned by others. Also mentioned by several, to solve the problem, you need to determine exactly what is the problem OR PROBLEMS.

 

Jon.

Edited January 14, 2017 by carbking (see edit history)

[Ben Bruce aka First Born]

  Agree with all Jon says except #6 last half. No starter button under footfeed on our Buicks. The starter switch is on the carb, activated when the footfeed is depressed.

 

  Ben

[carbking]

1 hour ago, First Born said:

  Agree with all Jon says except #6 last half. No starter button under footfeed on our Buicks. The starter switch is on the carb, activated when the footfeed is depressed.

 

  Ben

Thanks Ben, I was under the impression there was a switch on the floor under the footfeed. Obviously, thinking of something else (or maybe just not thinking  )

 

Jon.

[carbking]

On ‎12‎/‎31‎/‎2012 at 1:03 PM, Curti said:

Rerouting of the fuel pump to carb steel line away from the exhaust manifold, thereby increasing the distance from 3 inches to 8", then placing a length of easily removable mylar over the steel line.

I was told by an old timer that copper line disipates the heat better. An extrapalation of that is the reason that welding torches have copper tips. Even though copper melts at a lower temp than steel it dosn't because of the heat transfer properties.

Over the years, at least aluminum, brass, copper, and steel have all been used for factory fuel lines.

 

Personally, I would never use anything but steel UNDER the car (tank to engine compartment) due to tensile strength. If one does use copper, one should bend a "vibration loop" if copper were to be used from a fixed point (ie. frame) to a moving point (some part of the engine).

 

To my knowledge (not positive of this), the last use of copper fuel lines by any car manufacturer in the USA was Oldsmobile in 1966. Two of the lines connecting the 3x2 setup were copper.

 

Jon.

[Curti]

This is a 35-36 Auburn with the loop you describe Jon.  I have never had vapor lock with any of my Auburn , even idling thru the parade @102 degrees F

[JWLawrence]

I had a 47 Packard Custom Clipper with the starter switch on the carburetor. I have a strong personal dislike for this design. I find that always having to depress the accelerator pedal to start the engine under all conditions is not the best method. Why this design was used in Packards, Buicks, and others is beyond me except maybe to convey something "modern" in their products. It is easy to install a conventional starter switch by either using the wiring from the carburetor switch or wiring the starter switch in parallel with the one on the carburetor. Having the conventional switch allows for more flexibility in starting and engine whether it is a cold first start of the day of after it has been run and is up to operating temperature. Your personal preference may differ from mine.

 

(o[]o)

[Curti]

Well said Mr. Laurence !