Mikey Posted October 13, 2009 Share Posted October 13, 2009 So i recently built another l28 for my Z after my last motor lost the head gasket ( thank you fresno 112 degree weather.) so my problem, my instinct tells me the carbs are too rich. they flood on idle super easy. if its sitting at idle for more than 2-3 mins i can see the primary throats lined with fuel and it starts to choke and will soon die. part throttle they run just fine but my eyes burn like hell and it smells of unburned fuel. under WOT it sounds like its drawing enough air but its sluggish and gutless. off idle to WOT it just pops up the carbs and spits fuel back up and out. so any help would be greatly appreciated. and to let you all know what ive done. im on dual weber DGV's i checked the main jets, idle jets, air correction jets, venturi's, everything and they are all what is reccomended from weber and other members on this site. this is what ive got so far http://i43.photobucket.com/albums/e355/raceme54/240z/DSC02155.jpg Quote Link to comment Share on other sites More sharing options...
Mikey Posted October 13, 2009 Author Share Posted October 13, 2009 can anyone help me with this one? Quote Link to comment Share on other sites More sharing options...
Sam280Z Posted October 13, 2009 Share Posted October 13, 2009 How is your fuel level? Sounds high. The long and convoluted track of the manifold requires a rich mixture to prevent bogging on acceleration - but this sound too rich. I have had both DGV carbs and SU carbs. I recommend going back to SUs. Sam Quote Link to comment Share on other sites More sharing options...
Mikey Posted October 13, 2009 Author Share Posted October 13, 2009 ive got 3 lbs of fuel pressure at the T where it splits into both carbs id like to go back to SU's or tripples but money wont allow it since i just re built this motor. Quote Link to comment Share on other sites More sharing options...
Mikey Posted October 14, 2009 Author Share Posted October 14, 2009 still stuck... Quote Link to comment Share on other sites More sharing options...
Mikey Posted October 14, 2009 Author Share Posted October 14, 2009 i think im just going to set it on fire and call it a day Quote Link to comment Share on other sites More sharing options...
PanzerAce Posted October 14, 2009 Share Posted October 14, 2009 ive got 3 lbs of fuel pressure at the T where it splits into both carbs id like to go back to SU's or tripples but money wont allow it since i just re built this motor. Fuel level isn't the same as fuel pressure. Have you tried any adjustments at all to the mix screws? Quote Link to comment Share on other sites More sharing options...
Mikey Posted October 15, 2009 Author Share Posted October 15, 2009 Fuel level isn't the same as fuel pressure. Have you tried any adjustments at all to the mix screws? whoops i read it as fuel pressure... i have. i checked the jetting in the carbs and they are spot on. the way i set them is like so: screwed them out to high idle to my vac gauge then backed them in 1/4 turn Quote Link to comment Share on other sites More sharing options...
brokebolt Posted October 22, 2009 Share Posted October 22, 2009 if its sitting at idle for more than 2-3 mins i can see the primary throats lined with fuel and it starts to choke and will soon die. part throttle they run just fine but my eyes burn like hell and it smells of unburned fuel. under WOT it sounds like its drawing enough air but its sluggish and gutless. off idle to WOT it just pops up the carbs and spits fuel back up and out. http://i43.photobucket.com/albums/e355/raceme54/240z/DSC02155.jpg Love the pic. Classic. I would say the needle and seats are not properly sealing due to the verb-age that you see fuel lined the primary at idle. The carb will meter the fuel at the same rate at idle with all things being equal. A rising fuel level will introduce more fuel as time elapses. Check to make absolutely sure the needle and seat are indeed sealing. A electronic fuel pump is great for this. Hook it up and see if the fuel bowls flood with the engine off. This is also a great way to set the fuel bowl floats as it is static and not dynamic testing. You can also see if your fuel pressure is holding constant too if you use a fuel pressure regulator. Weeping needle and seats are a problem with any carb, DGV, SU, side draft... any carb that uses a needle and seat. If the needle and seat do not seal and the consumption of fuel at idle is too little then they will over flow into the carb choke. Also make sure the cam, and ignition are timed correctly to the crank. On a new rebuild it is possible that it is not correct during the assemble process (I rebuild a distributor once that was 180 out. But I swore it was correct. It was not.). Just cover your bases with a simple check at TDC to ensure your engine is 100% correct. Easy to do. Worth the time to check this vs. trouble shooting a carb by far. Use a return line too, as if you do not, then as the engine idles the fuel pressure *can* rise due to lack of fuel consumption and increase fuel pressure due to natural pump pressure rise. If your using a stock pump best bet is your pressure will remain constant as it is spring driven after it reaches maximum resistance. To answer your direct question it sounds rich at idle. Those other conditions point me in the direction of incorrect timing of the cam to crank. Happy wrenchin. Quote Link to comment Share on other sites More sharing options...
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