Quadrajet Problem Solving > Dialing in your rebuilt Quadrajet carburetor
Poor Idle On Rebuilt Carb
von:
Sounds to me like the intake getting air from somewhere with the throttle blades closed. First I'd check to make sure there is play in the linkage rod on the driver side that goes from the primary to secondary throttle shafts. No play could mean it's holding the secondary throttle plates open a hair at idle. If no help there I'd plug the .081 idle air bypass. A 326 with stock cam wouldn't need it IMO. Also I'd check to be sure your distributor vacuum advance can doesn't have a vacuum leak and also that the carb choke pull-off doesn't leak vacuum. Plus, I've seen Q jets where the choke fast idle screw (down low on pass side) is adjusted too far to let the primary throttle blades close enough for warm idle. Try backing it off (counterclockwise) a little.
D Denzin:
--- Quote from: 429bbf on March 17, 2015, 08:40:59 PM ---id say your float is ether set to high or your needle and seat are leaking ,or your seal on your seat is leaking . what your saying is you are flooding at idle? did you get the gasket under the seat nice and clean before you installed the new one?and did you install a new gasket under the seat. i hate to ask these questions but one little spec of crap will cause the problems you have. do you have a choke is the pull off working?is the choke wide open?fwiw
--- End quote ---
I'll check on the needle and seat tomorrow. I have a electric choke, its seems to be working, closed when cold, engine runs on a faster idle, opens up as engine warms. Choke is wide open when warmed up fully. Thanks for the ideas, will check and report back.
D Denzin:
--- Quote from: von on March 18, 2015, 01:30:23 AM ---Sounds to me like the intake getting air from somewhere with the throttle blades closed. First I'd check to make sure there is play in the linkage rod on the driver side that goes from the primary to secondary throttle shafts. No play could mean it's holding the secondary throttle plates open a hair at idle. If no help there I'd plug the .081 idle air bypass. A 326 with stock cam wouldn't need it IMO. Also I'd check to be sure your distributor vacuum advance can doesn't have a vacuum leak and also that the carb choke pull-off doesn't leak vacuum. Plus, I've seen Q jets where the choke fast idle screw (down low on pass side) is adjusted too far to let the primary throttle blades close enough for warm idle. Try backing it off (counterclockwise) a little.
--- End quote ---
I already checked the linkage rod from the secondaries to the primaries, OK there.
I'll look into all the other suggestions that are "easy" checks and leave the plugging the Idle Bypass till last.
I'll check into the vac advance, I did check operation before putting dist in by applying vac to be sure it worked, to be honest didn't check to see if it would hold and not leak down. Also checked the choke pull off but again for operation not if it held with a leakdown.
I'll check the screw on the choke to be sure its not holding up the primaries.
Thanks for the suggestions will check tomorrow and report back.
D Denzin:
429bbf,
Checked float level, was 9/32, changed it to 13/32 as spec'd in rebuild sheet.
Disassembled seat and checked gasket and mating surfaces. All looked good reassembled.
I don't have the degrading idle anymore. Your excellent advise on checking float level helped.
Von,
Secondary to primary rod was OK as I mentioned before, so I plugged the .081 Air bleeds.
I also checked the the vac advance and the choke pull-off. Both held vac without leaking down.
I also backed off on the choke fast idle screw, it wasn't touching, made no difference.
So now I can get it to idle down to 680-700 with pvc attached and vac advance attached to manifold vac. Idles very nice and smooth. If I slowly work the Idle mixture screws in it won't reduce idle, just degrades it till the engine runs rough and dies. I can back the idle adjustment screw on the throttle blades all the way out and the slowest idle I get is 680-700.
If I pull the PVC it will idle down to like 550 or maybe even less. If I pull the vac advance and plug or switch it to the ported vac source I can get the idle down. But the idle is rougher.
The timing is set at a total of 34 deg all in. Intial timing is 12 btc. When at Idle with vac advance on man. vac I get about 24 total at the 680-700 idle.
I'd like to get the idle down to about 600-625. I can do it with no PVC or ported vac for the dist advance but then the idle is rougher. Seems like idle is lower cause the engine is struggling. Maybe I should work on getting a better idle quality using the ported vac. At 680-700 with vac advance on man vac and pvc attached the idle is silky smooth. I'd just like to knock it down about 75 rpm's.
Von, I think your suggestion of plugging the air bleeds helped knock the idle back about 100 rpm's. Thanks!!
Anymore ideas to help me over the hump?
Thanks both Von and 429bbf for your help so far!!
77cruiser:
Are your throttle plates adjusted evenly? You might try a different PCV valve some have different ratings for the amount of air they pass.
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