i think some one on here was having a weird fuel leak problem - not a normal leak . any conclusion ? have an older ( even older than me ! ) guy , has a 64 era vette ( oem carter carb # 3720 auto , #3721 manual ) . problem is if he parks it for a short while has to pump it extra and then it kicks out alot of black smoke and then settles down ok . if he parks it for 2-3 days then has to pump alot extra , more black smoke , then seems to run ok . from his description he makes it sound like the fuel is dissappearing ? no gas in oil . no external leaks . and like i said this is his explanation . he is familiar with car stuff ( vettes mainly i think ) but by his own addmission not with carb function . and not a good listener when i tell him something or explain something .
It's the "modern" fuel we all have to use. Made for enclosed systems, it'll evaporate quickly out of a carb every day of the week. I had the resto shop hook up an electric pass-thru fuel pump that only runs when the key is in either the ACC or "start" position. Once the engine fires, it loses power and shuts off, since the mechanical pump does all the fuel movement work at that point. When it sits for a while, I just turn the key to ACC, wait for the pump to fill the bowl, pump it twice and start the car. No more "crankity-crankity-crankity-crankity-crankity-crankity..." (you get the picture). See if your friend thinks that might be a solution. Joe
update from owner - has to dribble gas into carb to start after a few days of sitting . i'm gonna get carb(s) back from guy today sometime and go through them , dbl check my steps etc . they are pretty simple so --- ? good idea on the fuel bowl fill , will try that . and the carb with bad idle ( after I just did it for him ) , that had a throttle bore idle screw hole problem - previous rebuilder ( or someone ) actually screwed the idle screws in so hard that it busted open the hole at the throttle bore side . nice . I had to adjust by "eye" and told him he would have to level it out after start up .
carb #1 - #3720 . gave it back to him , test run , runs good but no idle quality ( this was the carb that a previous rebuilder had tightened down the idle screws so hard that they actually broke away some of the aluminum in the throttle bore area . so bad idle quality was gonna be suspect for sure ) . got it back and swapped lower section from his parts carb , reassembled , back to him saturday for test run . no word back yet . carb #2 - #3721 . this is the one with the "overnight" fuel leak ( disappearance ) problem . took it apart , filled fuel bowls with water for a day or two - still there ? and I had it in a metal pan , no moisture in pan . noticed a few things about the carb , mainly linkage problems . and the two rear cluster gaskets were WAY off center - i'm wondering if something there could have caused a siphon effect ? but he claimed no gas in oil ? is there a way it could move in reverse back towards fuel pump ? almost like internal carb pressure would push fuel in that direction , but that would mean the fuel level would be above float and booster/cluster level in parts of carb ? just thinkin .
stopped at his house yesterday coming back from PA . installed the 3720 carb with the bad idle screw problem - had a spare 3720 for parts , used that base - seemed to run out pretty good . I also had his 3721 done ( fuel leak ? carb ) , he's gonna test that a little and let me know . but he's running out of threads on his fittings from tinkering with the carbs back-n-forth so much . bunch of right angle and 45 degree brass fittings from pump to filter to carb . I told him he might want to clean that mess up .
update - 3 carbs , 3 pretty standard rebuilds to instruction/common sense guidelines . installed and trial ran all adjusting idle etc as we went along . all seemed pretty good and to his satisfaction . now if he will just leave one carb on there and quit screwing around he'll be ok . he uses the original AC Delco-GM fuel line mess from pump to carb - I suggested he clean that up and run a simpler set up . told me he does not want to "mickey mouse" it ! jeez , mr original . of course he doesn't worry too much about dripping gas all over the fender .
