Carb stuff, why is it doing this???

[ryan68]

Ok, carb problems, continue. I got a 795cfm Edelbrock Q-Jet, my motor is freshly rebuilt and for some reason the carb still dribbles fuel out from the top of the primaries. I took it apart twice to check the float level and it's fine, needle and seat are fine. What could be the problem? And I don't have any sort of high volume fuel pump. If I turn the idle mixture screws all the way in, the truck still runs.

[72C203503ONTHETREE]

It sounds like your throttle blades are open too far for some reason and the main jets are starting to work, the reason the idle screws dont make a difference is that they aren't being used, no vacuum present at the idle passages in the throttle plate. Only thing I can think of that will do that, if the idle speed is near 1000 or less, is that you have a vacuum leak that is letting in too much air and you had to adjust the idle up high enough that the main jets are now being used to make up the difference.

[hgs_notes]

I had this problem before too. With my original stock fuel pump it seemed to have too much pressure for the needle and seat to stop the fuel flow. I bought a Holley fuel pressure regulator and set the pressure to what stock is supposed to be and never had a problem again. This was years ago so dont ask what the pressures were, I dont remember. I'm still using the same set up though. I hope my pump lasts forever.

HG

[Harold Shepard]

Stock Gm pump non electric should put about 5 in/ lbs of pressure to the carb many of them don't, I think average is about 3 in/lbs (may be using wrong units) but anyway anything over about 7 will blow past the stock needle and seat.

[ryan68]

I'll try the fuel pressure regulator, luckily I have one sitting out in the garage. I did this last time and set it up for 6psi, and it still did this, do I need to go to 5? I might jet the mains down a little bit too.

[ryan68]

Ok, tried the fuel pressure regulator, and took it down to 2psi and it still did it. I kinda noticed this before, but it really only is coming out from the passenger side primary. Any new ideas?

[ChevLoRay]

www.edelbrock.com

They have a technical section that lets you download manuals and trouble-shooting material. Check it out. Off-hand, I'd have to say that the float level seems suspect, but you say it isn't. You'll want to watch screwing in the idle air screws too tightly. It's easy to put a groove in the machined taper part and that will screw up your idle, too.

Go to the website and check it out.

[ryan68]

Pulled the carb off, and tried to run my other Q-Jet, but I don't have any choke or throttle linkages so that didn't work to test anything. The throttle plates on my carb seem to be open when it's at idle. By open I mean I can shine a flashlight on it and see light on the other side. Somewhere a little bit smaller than a pencil lead they are open. Could this just be sucking fuel out from the bowl?

[72C203503ONTHETREE]

Read my post after your original post, if the throttle plates are opened too far they idle cicuit won't function right.

[ryan68]

Yeah, but should they seal all the way? And since they are open, how do you adjust them so they close?

[72C203503ONTHETREE]

They wont completely seal off, theres a slot where the fuel comes out but if you close them too far it will not idle either. There is a screw on the drivers side that contacts the throttle arm(where the accelrator cable is connected to). First, screw the idle mixture screws all the way in but not very hard. Back them off about 1 1/2 turns, turn the idle speed screw out until the primary blades(small ones) are just about completely closed. Put the carb back on if you havent allready. If the carb is on the intake, just back the screw back until the screw end doesnt touch the throttle arm. Make sure the chole is not on when you do this since it will be set on high idle. Easy way to do that is to pull the throttle arm back and push the choke plate all the way open then while holding it open release the throttle arm. Set the screw so that it just moves the throttle blades/shaft. Start it like you normally do, let it warm up, then kick the choke off by hitting the gas a bit. It will probably die since the blades will most likely bee too closed. Try varying the gas pedal hieght with your foot, try to get it to run at whatever idle speed you want, usually around 900 to 1000 rpm. You will at least know if it will idle then. You can then start screwing the idle speed screw in until its set. You may have to mess with the mixture screws some but 1 1/2 turns out is usually close. Set your idlke speed then turn the mixture screws in until it starts to idle rougher, back them out a bit past where it starts running smoother and then reset the speed with the idle speed screw. If that doesnt work, you have a carb problem or a vacuum leak somewhere. Its kind of hard to diagnose over a forum, lol.

[ryan68]

I'm probably done what you've said a million times. Problem is at anything less on the idle screw the truck won't run.

[72C203503ONTHETREE]

Hows your timing? Are the idle air jets and fuel passages cleaned out? Have you checked for any kind of vacuum leaks?

[68C15]

just for reference the transfer slots should have 0.040" underneath the blades. more than that & you will be drawing from the main ckt.
is there a vac leak on the pass. side of carb? use propane to find leak.
is pass. blade bent?

[67_SS396]

Could be symptoms of a bad float. Check for small pin holes in the floats or if they are full of fuel.