Aitch Posted May 30, 2023 Report Share Posted May 30, 2023 My ’79 Spitfire 1500 is in the process of being recommissioned. Methodical and common sense approach taken and now coming to the carbs (twin SU HS4) etc. Carbs cleaned, petrol in bowls, gaskets good, floats correct height and free, no stiffness. Needles etc. all OK, no stickiness or any signs of being gummed up, after a long standing. All connections secure so no air leaks. However, when I turned the engine over I had petrol coming out of the ‘Overflow Pipe’? Only happens on the LH Carb (nearest the bulkhead), RH carb OK. The car didn’t have one and ran OK after I bought it. I have taken 100’s of photos of the car before I commenced any work, so am baffled as to whether I should have one. My photos don’t show one. The petrol was leaking from the stub pipe just below the jubilee clip in the picture. Have checked the Haynes Manual, no mention. Rimmer’s show a diagram for an overflow line (Front 125170 hose, Vent Pipe 215924) but I do not know if this is what I need, or for that matter how it fits, or where it goes to. Any suggestions? Thanks, Aitch Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 30, 2023 Report Share Posted May 30, 2023 any messing with the fuel hoses make the dreaded rubber slivers especially if the hose is fake /poor quality these little sods get shaved off when inserting metal into the rubber hose they float about and jam the back of the float needle its a very common problem they bread like rabbits i would remove the float needle and look behind it , also pump some fuel int a jar , might catch some the other idea would be many after market pumps put out excessive pressure if you have replaced it then that can over power the float needle and fuel again pours out the vent tube Pete Link to comment Share on other sites More sharing options...
Aitch Posted May 30, 2023 Author Report Share Posted May 30, 2023 Fuel lines are about 1 year old and good quality. Fuel pump is original, appears in good condition and no c**p in the filter. Good flow to the carb inlet. When I checked the carb needles etc. about 2-3 weeks ago before proceeding with the further work, all appeared OK. Perhaps, it has pulled some 'rabbits' through. Still baffled by the vent though? Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 30, 2023 Report Share Posted May 30, 2023 the vent is just an open outlet in the top cover , nothing special but fuel will flood out if the fuel height is uncontrolled by excess pump psi rabbits or any other float defect i had problems with the HS4s on my 2000 the float needle platform had worn a small ridge which stopped the float running smoothly 2 new floats and bingo never another problem Pete Link to comment Share on other sites More sharing options...
Aitch Posted May 30, 2023 Author Report Share Posted May 30, 2023 Thanks for that, something for me to pursue. Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 31, 2023 Report Share Posted May 31, 2023 i tried to reface the platform on the float but its funny stuff and even fine wet dry just makes it worse new float and my hate of anySU was revived to success these are the plastic float with the non adjustable needle contact pad needs a magnifier to spot the grooves Pete Link to comment Share on other sites More sharing options...
Iain T Posted May 31, 2023 Report Share Posted May 31, 2023 I had a 1500 Spitfire in the mid 70s that dribbled petrol. I went to a local motor factors who said yes it's currently a common problem with SUs. He supplied two Jaguar spec coated float valves which cured the problem. The originals didn't seal. Iain Link to comment Share on other sites More sharing options...
Aitch Posted June 2, 2023 Author Report Share Posted June 2, 2023 Following the suggestions, I removed the offending bowl to find that the needle had somehow dropped to the bottom of the carb bowl. Virtually new in appearance, so replaced and then checked the other carb bowl, but no problems there. All back together and overflow has stopped and not now a problem. Thanks to all. Aitch Link to comment Share on other sites More sharing options...
Pete Lewis Posted June 2, 2023 Report Share Posted June 2, 2023 thats a good one to own up too Ha ! pleased its all ok now Pete Link to comment Share on other sites More sharing options...
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