General Category > Quadrajet Carb Talk and Tips

no control of idle mixture screws

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1bad79:
found the cam card howards cam intake .560 278 duration exhaust .555 282 duration lobe center 110 intake c/l 106 the cam was degreed in 4/7 swap cam if it makes a difference the other engine info is above  idle tube .038 down channel .055 upper air bleed .067 lower air bleed .067 bypass air .059 hole under mixture screw .089 74 jets 44 primary rods DA secondary rods 1/4 inch float setting  n/s was vacuum checked along with 3 other ones and none hold, I tried with the top off  to watch what happens and at about 2.5 pounds it wont hold,all the parts came from cliff about 3 years ago so they have been sitting along time, maybe the rubber tip dried out on the needle? so I guess I need a needle and seat for sure then retry, i am running an electric pump with a bypass regulator at 4.5 psi is this to much pressure? let me know if mor info is needed thanks steve

Cliff Ruggles:
I'd add a little more idle bypass air and correct the flooding issues and you will be fine.

I've never seen one of our Viton needle tips "dry out", and we've had next to no issues at all with them to date.  You might try lightly smacking the seat with punch and spare check-ball, or replacing it with a new N/S assembly.

Once the flooding issues are fixed, then you can effectively evaluate the carburetor and tune it for the engine if/as needed.....Cliff

1bad79:
im going to work on it tomorrow, thanks for the response cliff  thanks, steve

1bad79:
fixed up the n/s and went .104 on the bypass air seems to work good but its really erratic at idle so I have some other issues to track down thanks for the help

1bad79:
I worked on my car some tonight again I had some erratic timing so I pulled the chinesium distributor and installed the best gm one I had that took care of a lot of the issues but it still idles like complete crap.  I tried multiple things even manifold vacuum to the vacuum can this seems to be the most effective thing I did but now it wouldn't idle below a 1000 even with the plates shut all the way but it was smother so I re read the part in cliffs book about the idle circuit and think I discovered an issue with the carb I thought the upper air bleeds were in the air horn and just below were the lowers but I think I was mistaken and believe I have 2 sets of upper air bleeds one next to the tapered screw and one just below in the carb body, does this carb have the wrong air horn? or am I just wrong on what the function of those holes are I have a pic but I guess its to big as I cant post it thanks steve

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