Quadrajet Problem Solving > Diagnose a Quadrajet carburetor problem

nozzle drip again

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bsblguy:
1969 GTO 400/350 automatic. Idle tube is .038, idle down channel .046, upper air bleed .048, lower air bleed .068. idle air bleed screw is seated. Timing at 12 btdc. I do not have cam specs but it seems there is a mild cam in it, all else is stock. I put you kit in it with 72 jets, don't remember meter rod size. All was pretty good, idle a little rough in gear at 650, set it up some to be 650 with ac on. My accell hei dist. decided not to work so I put in a pertronix flame-thrower hei. Now my nozzle drip is back. Only thing changed was dist. Timing set at 12 btdc like it was. Don't know why this happened, doesn't make sense to me. What do I do to fix this?  7029268 carb.

omaha:
   Well, normally to stop the nozzle drip you would add some bypass air BUT, to experiment a bit, you can pull a vacuum line temporarily to see if bypass air is what is needed. Pull a vacuum line (small one) and see if the rpms will increase without opening up the throttle plates. Jus pull the line and proceed to adjust the idle like normal with a vacuum gauge. If you can get the rpms to come up without the plates opening farther, then you know that you can close them up a bit and hopefully stop the nozzle drip. Then, basic math you can determine the size of the idle bypass if they are added to the carb. (from the size of the vac line that was pulled, internal diameter of the tube is measured). Do you mean to say that you actually have a carb with the screw on the idle airbleed passage, I have never seen one of those and would not even have the slightest idea how to adjust it. does it bypass air with it fully seated? Would like to see a pic of that. Good luck!

Cliff Ruggles:
Not enough idle fuel to the mixture screws or not enough bypass air, or both.  I'd open up the down channel restrictions to .052" and open up the bypass air slightly and see if this helps?  Having an "unknown" cam makes giving advice difficult.  How much vacuum is the engine making at 700-750rpm's idling?....Cliff

bsblguy:
Grabbed the wrong drill bit and opened up idle down channel to .059, upper air bleeds at .060. Set idle at 750 and vacuum is 13 inches. No more nozzle drip but have to set idle to about 980 to get 650 in drive and still a little rough idling in drive. Turning ac on in drive drops idle to about 580. I have a solenoid I can put on for ac idle speed. Do I need to close up the idle down channel some? It seems to be way to much drop from neutral to in gear.


omaha look at page 27 of Cliff's book and you can see the idle air bleed screw, that is the carb that I have. It does not like it opened at all.

omaha:
vac advance in the ported source of the carb? This is what has come to mind because of the dist. change. Maybe the new vacuum can starts to work earlier (at a lower vac reading) this is what could be causing the drop in rpms. When the engine is in neutral, the can may be adding timing which could raise the rpm's and then when you put a load on it it slows the engine jus enough to put less vac at the dist. hence the timing retards and in turn the rpms drop off even more. The more load, more they drop. Usually this problem is more pronounced when there is low compression and way larger than stock camshaft is used. In this situation you need to be 100% sure your dizzy is in the "ported source."
If it is in there, disregard this advice. Depending on the cam (I have a feeling it is somewhat large) you will need bypass and more fuel so I think the booboo with the .059 idle channel restriction you may be able to get away with.
Good luck!

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