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Another AFB Question - Sorry.....

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  • Joel T.
    Expired
    • April 30, 2005
    • 765

    Another AFB Question - Sorry.....

    Guys;

    More strange stuff going on with my (second) AFB... My first AFB had a problem with flooding the engine... Drive the car for a few miles, shut it down say to fill it up with gas, go to start it and it is flooded... Press your foot to the floor, crank it and it will kick over after some a few turns. I yanked that carb and put it on the bench to be eventually rebuilt.

    I picked up a second AFB which I rebuilt myself. That carb has new floats, new needle seats, new jets and rods, etc.. I installed it on the car and it ran great.. and what was the best part, no more flooring when warm... that is until today!

    I went with some friends to the DelVal Covered Bridge Tour today. One of the guys following me tells me that my car is running really rich, when we are creeping through the small towns.. He is behind me and my exhaust is making his eyes burn! When I shut the car down at rest stops and go to start it again, it is flooded, big time!!

    I suspect that this can't be related to any more than a few things... our crummy new gas (but it is not all that hot out today), the effect of ethanol on the needle seats (only 2-3 months old). too much pump pressure (running a repop)...

    This is now the second AFB to be installed exhibiting exactly the same problem with flooding, so I got to believe that this is related to something other than to the carbs themselves... Any thoughts and /or suggestions will be greatly appreciated!

    Thanks,

    Joel
  • Clem Z.
    Expired
    • January 1, 2006
    • 9427

    #2
    Re: Another AFB Question - Sorry.....

    Originally posted by Joel Talka (43778)
    Guys;

    More strange stuff going on with my (second) AFB... My first AFB had a problem with flooding the engine... Drive the car for a few miles, shut it down say to fill it up with gas, go to start it and it is flooded... Press your foot to the floor, crank it and it will kick over after some a few turns. I yanked that carb and put it on the bench to be eventually rebuilt.

    I picked up a second AFB which I rebuilt myself. That carb has new floats, new needle seats, new jets and rods, etc.. I installed it on the car and it ran great.. and what was the best part, no more flooring when warm... that is until today!

    I went with some friends to the DelVal Covered Bridge Tour today. One of the guys following me tells me that my car is running really rich, when we are creeping through the small towns.. He is behind me and my exhaust is making his eyes burn! When I shut the car down at rest stops and go to start it again, it is flooded, big time!!

    I suspect that this can't be related to any more than a few things... our crummy new gas (but it is not all that hot out today), the effect of ethanol on the needle seats (only 2-3 months old). too much pump pressure (running a repop)...

    This is now the second AFB to be installed exhibiting exactly the same problem with flooding, so I got to believe that this is related to something other than to the carbs themselves... Any thoughts and /or suggestions will be greatly appreciated!

    Thanks,

    Joel
    turn the carb upside down and pressure test the needle/seats for leak thru. here is what i use for this pressure check. i pump up the pressure using the squeeze bulb and at the desired pressure on the gauge i close the snap valve at the bottom of the gauge to see if the pressure drops indicating a leak thru.
    Attached Files

    Comment

    • Stuart F.
      Expired
      • August 31, 1996
      • 4676

      #3
      Re: Another AFB Question - Sorry.....

      Joel;

      Any chance you may have some old time miladies like dirt in the fuel or perhaps thread tape? how recent is the filter?

      Beyond that, we know our AFB's are very touchy about today's crappy gas. If your carb is running hot, be it ambient causes or engine related heat from the heat riser, it does not take much to cause a percolation condition. Use an IFR gun to check for hot spots, and specially see how hot the carb is getting. I hate to tell my story again, but I had had enough; I did everything I could to reduce the carb temp (I don't recall; is yours the L-75 or L-76?). I installed an L-75 phenolic base plate with two L-76 gaskets, used a hose from the filter to the carb (had to), went to an electric choke w/o heat/fresh air tube, and installed Tomco inlet valves which allowed me to lower the float levels as they flow much better. Bottom line was I reduced the carb temp at full hot by some 40 to 45 degrees or so (I'd have to check my notes). With a full functioning heat riser valve, my RH manifold runs about 180 degrees hotter than the LH manifold. Wiring the valve open will drop that significantly, replacing it with a fuelie spacer is even better.

      Beyond that, I rejetted my carb, both fuel and air bleeds. I no longer have any problems with the carb. I was too certain of my gains; however, and went to a 180 degree thermostat (in place of my 160) and paid the price with a stuck thermostat. The engine idled in traffic a long time and it hit 195+ degrees, but still ran very smoothly. As noted in my recent poston the way home, I had a short block overheat and purge which almost cost me my original engine. Thanks to an all cast iron engine and the L-76 by-passes, it survived unscathed.

      Stu Fox

      Comment

      • Timothy B.
        Extremely Frequent Poster
        • April 30, 1983
        • 5186

        #4
        Re: Another AFB Question - Sorry.....

        Joel,

        There could be a problem in the fuel tank with rust and the fine particals are getting through the sock and filter eating the needle and seats. Do you know the history of the tank, is it original?

        Comment

        • William C.
          NCRS Past President
          • May 31, 1975
          • 6037

          #5
          Re: Another AFB Question - Sorry.....

          I assume you are using the phenolic block and stainless steel plate under the carb?
          Bill Clupper #618

          Comment

          • Stuart F.
            Expired
            • August 31, 1996
            • 4676

            #6
            Re: Another AFB Question - Sorry.....

            Joel;

            One other item you might want to check when you tear into your AFB; I read somewhere that there was some inferior gaskets provided with the needle/seats in some kits (seal from seat to top plate). They were said to be dimensionally too small in the width of the gasket seal surface, and too large an I.D.. That, coupled with their being made of a material that may be easily attacked by the Ethynol would bring about a leak around the needle/seat bases.

            If you can find a kit either with the Tomco Valves, or one marketed under that name, you'd be doing yourself a favor. I lucked into finding several from Eckler's. They had a sale on a few years back so I ordered sight unseen and they happened to be provided with the valves. The valves use a Viton Disc and a plunger pin. They discharge through holes around the side of the barrel instead of just past the needle, and therefore flow a larger volume of fuel, yet seal as good or better. They allow you to drop your float levels, as I mentioned before, due to the higher flow rate. Also, and this has to do with the seat seal mentioned above, they have a hex "float" end on them which allows using a socket and 1/4" drive to tighten them in place instead of a broad blade screw driver (which I never liked).

            One concern I have with them; however, is that I think a portion of the discharge holes may be above the top plate gasket (not sure). Reason being is that I've noticed fuel "sweat" around the top plate gasket surface edge. I have not confirmed this as yet - it may just be that I used the gasket more than once. If indeed that is the case, my idea was to do some gasket t******* to open up more area of the gasket above the float chamber. Right now they come with only a couple of say 1/4" vent holes.

            FWIW;

            Stu Fox

            p.s. I'm up at this hour as I have a bad cold and can't sleep, Ha!

            Comment

            • Joel T.
              Expired
              • April 30, 2005
              • 765

              #7
              Re: Another AFB Question - Sorry.....

              Originally posted by Clem Zahrobsky (45134)
              turn the carb upside down and pressure test the needle/seats for leak thru. here is what i use for this pressure check. i pump up the pressure using the squeeze bulb and at the desired pressure on the gauge i close the snap valve at the bottom of the gauge to see if the pressure drops indicating a leak thru.
              Clem;

              Thanks, I will give that a shot... I can start with the carb sitting on my bench... If the needle seats are functioning properly, what pressure should they be able to withstand w/o leaking down?

              Joel

              Comment

              • Joel T.
                Expired
                • April 30, 2005
                • 765

                #8
                Re: Another AFB Question - Sorry.....

                Originally posted by Timothy Barbieri (6542)
                Joel,

                There could be a problem in the fuel tank with rust and the fine particals are getting through the sock and filter eating the needle and seats. Do you know the history of the tank, is it original?
                Tim;

                The fuel tank is original but has no rust or other junk in it... I've checked that a while back when I was having that fuel starvation problem... I checked the tank and the sender/sock, blew out the lines, etc... She is clean as a whistle.

                Thanks!

                Joel

                Comment

                • Joel T.
                  Expired
                  • April 30, 2005
                  • 765

                  #9
                  Re: Another AFB Question - Sorry.....

                  Originally posted by William Clupper (618)
                  I assume you are using the phenolic block and stainless steel plate under the carb?
                  Bill,

                  Nope... This is a straight stock installation... right out of the book. Where would I pick up a phenolic block ans stainless steel plate?

                  Thx,

                  Joel

                  Comment

                  • Joel T.
                    Expired
                    • April 30, 2005
                    • 765

                    #10
                    Re: Another AFB Question - Sorry.....

                    Originally posted by Stuart Fox (28060)
                    Joel;

                    Any chance you may have some old time miladies like dirt in the fuel or perhaps thread tape? how recent is the filter?

                    Beyond that, we know our AFB's are very touchy about today's crappy gas. If your carb is running hot, be it ambient causes or engine related heat from the heat riser, it does not take much to cause a percolation condition. Use an IFR gun to check for hot spots, and specially see how hot the carb is getting. I hate to tell my story again, but I had had enough; I did everything I could to reduce the carb temp (I don't recall; is yours the L-75 or L-76?). I installed an L-75 phenolic base plate with two L-76 gaskets, used a hose from the filter to the carb (had to), went to an electric choke w/o heat/fresh air tube, and installed Tomco inlet valves which allowed me to lower the float levels as they flow much better. Bottom line was I reduced the carb temp at full hot by some 40 to 45 degrees or so (I'd have to check my notes). With a full functioning heat riser valve, my RH manifold runs about 180 degrees hotter than the LH manifold. Wiring the valve open will drop that significantly, replacing it with a fuelie spacer is even better.

                    Beyond that, I rejetted my carb, both fuel and air bleeds. I no longer have any problems with the carb. I was too certain of my gains; however, and went to a 180 degree thermostat (in place of my 160) and paid the price with a stuck thermostat. The engine idled in traffic a long time and it hit 195+ degrees, but still ran very smoothly. As noted in my recent poston the way home, I had a short block overheat and purge which almost cost me my original engine. Thanks to an all cast iron engine and the L-76 by-passes, it survived unscathed.

                    Stu Fox
                    Hi Stu;

                    Mine is an L-76 340HP car like yours... I'm running a straight stock configuration with the only exception being that I have that spacer in the RH manifold versus the heat riser valve....

                    The carb is a tad richer than stock; primary, secondary and rods. I calculated it after I put it together and we are talking about only 3-4% more fuel than straight stock... not a lot.

                    The problem seems to be worse when the engine is hotter... but I have had it happen even after a short trip; like 4 miles, going from my house to the local gas station I use (Exxon)... Yesterday was like 55 degrees and the car was running good... It was well warmed up when we hit the small towns... After a stop, and a flooded restart, I stood behind the car and could smell it too.. Later on in the day, I had the car cooled down and Idling... no stink.

                    Would the percolation cause the flooding, or would it cause other symptoms as well?

                    Thanks,

                    Joel

                    Comment

                    • Clem Z.
                      Expired
                      • January 1, 2006
                      • 9427

                      #11
                      Re: Another AFB Question - Sorry.....

                      Originally posted by Joel Talka (43778)
                      Clem;

                      Thanks, I will give that a shot... I can start with the carb sitting on my bench... If the needle seats are functioning properly, what pressure should they be able to withstand w/o leaking down?

                      Joel
                      i test at 8 to 9 pounds

                      Comment

                      • Terry B.
                        Expired
                        • December 1, 1988
                        • 111

                        #12
                        Re: Another AFB Question - Sorry.....

                        If my memory serves me correctly, I had some similar problems years ago. One was caused by leaking plugs in the base of the carb but was more of an issue with starting after extended setting. The other was more closely related to your type of problem and it was caused by excessive fuel pump pressure that pushed fuel past good needles and seats.

                        Comment

                        • Stuart F.
                          Expired
                          • August 31, 1996
                          • 4676

                          #13
                          Re: Another AFB Question - Sorry.....

                          Joel;

                          When I had my percolation problem, you could look into the carb and see the fuel spewing out of the nozzles in the cluster booster venturis. I know you probably would not want to follow my mods as using the phenolic spacer from the L-75 will require you use a fuel hose from the filter to the carb. The chrome steel line is too short. But, if you do, you do not need the thin stainless steel plate from the L-75 - just the phenolic spacer with two (2) L-76 base gaskets - in a sandwich. That spacer alone accounts for nearly 45 less degrees of temperature at the carb. Believe me, that means a lot.

                          Again, when you check your other carb using pressure as Clem advised, remember if it leaks it could be the needle/seat gaskets as I previously mentioned. There are a lot of bad ones out there.

                          Keep us posted. I'm sure you have enough info and talent to solve this problem to your liking.

                          Stu Fox

                          Comment

                          • John H.
                            Beyond Control Poster
                            • December 1, 1997
                            • 16513

                            #14
                            Re: Another AFB Question - Sorry.....

                            Originally posted by Joel Talka (43778)
                            Where would I pick up a phenolic block ans stainless steel plate?

                            Thx,

                            Joel
                            Joel -

                            Long Island and Doc Rebuild have them, and so do the rest of the usual vendors - they're not rare parts.

                            Comment

                            • William C.
                              NCRS Past President
                              • May 31, 1975
                              • 6037

                              #15
                              Re: Another AFB Question - Sorry.....

                              By the way, the phenolic block and stainless steel part ARE by the book, (Check the AIM) specifically to avoid the type of problem you are seeing. Your exhaust heat crossover is putting hot exhaust gas directly onto the base of the AFB, and the AFB needs a system to keep the hot exhaust off the aluminum bottom as the heat transfer will boil the gas. That was in the 60's with good gas, Much more important today.
                              Bill Clupper #618

                              Comment

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