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Topic Review (Newest First)
10-25-2011 07:15 AM
69chevyLWB
Quote:
Originally Posted by skyraker
One thing that has not been spoken of here is the windup spring on the secondary throttle plates. If the windup is too weak, the car will bog on heavy acceleration. There is an allen head set screw, and the plate shaft is slotted on the end. By loosening the allen screw and turning the windup shaft the tension on the seconday plates can be changed. I always did it by feel, but I am sure that there is a better way to get it just right. Skyraker.
When i said air valve spring i am referring to the "windup" spring on the secondaries.
10-24-2011 07:23 PM
skyraker
secondary windup

One thing that has not been spoken of here is the windup spring on the secondary throttle plates. If the windup is too weak, the car will bog on heavy acceleration. There is an allen head set screw, and the plate shaft is slotted on the end. By loosening the allen screw and turning the windup shaft the tension on the seconday plates can be changed. I always did it by feel, but I am sure that there is a better way to get it just right. Skyraker.
10-24-2011 06:02 PM
V8&4spd
Quote:
Originally Posted by 69chevyLWB
I did forget to mention that i floored it once and it backfired once through the carb and i never floored it again incase of back things happening.
Float level is set to spec. needle and seat were vacuum checked. idles tubes are intact but holes in top are very small compared to another carb i had apart. Ignition is all up to snuff. swapped another working qjet on today so i could drive it too church and ran very well. the jets are 71 and the rods are from a remanufactured carb so i couldnt tell you what they are. has G hangar and also remaned secondary rods. air bleeds have brass restrictors driven into them. i told cliff this when i ordered parts and he said it was definetly a remanufactured carb if that means anything to you. choke pulloff works fine releases at precisely 2.3 seconds. set the air valve spring to factory spec which is 3/4 of a turn.
Also APT is set at two turns from full bottom.
That is the reason I have multiple Quadrajets. You get some that work just right on one engine and they don't work worth a damn on another engine.
10-24-2011 04:24 PM
69chevyLWB to the top
10-23-2011 03:12 PM
69chevyLWB I did forget to mention that i floored it once and it backfired once through the carb and i never floored it again incase of back things happening.
Float level is set to spec. needle and seat were vacuum checked. idles tubes are intact but holes in top are very small compared to another carb i had apart. Ignition is all up to snuff. swapped another working qjet on today so i could drive it too church and ran very well. the jets are 71 and the rods are from a remanufactured carb so i couldnt tell you what they are. has G hangar and also remaned secondary rods. air bleeds have brass restrictors driven into them. i told cliff this when i ordered parts and he said it was definetly a remanufactured carb if that means anything to you. choke pulloff works fine releases at precisely 2.3 seconds. set the air valve spring to factory spec which is 3/4 of a turn.
Also APT is set at two turns from full bottom.
10-23-2011 06:46 AM
cobalt327
Quote:
Originally Posted by 69chevyLWB
Cobalt327
thanks for all the help!
it has a brand new distributor in it and the engine as been running before and i didnt change anything besides the carb. pcv is plumbed all plugs checked and distributor working fine. i think that is somthing i did wrong when i rebuilt it. it idles fine sometimes then others wont idle for crap. i have never been able to give it any amount of gas when i am driving or it just falls on its face. you can revv it to the moon when its just sitting in park but with any kind of load it just nosedives.
It sounds like it's way too rich. I say that because you've never mentioned it popping through the carb. Checking the plug color for being too rich should help decide if it is or not, or have someone follow you to see if it blows black smoke from the exhaust when it's acting up- this is also an indication of too rich.

Possibilities if too rich (this isn't everything, just what I could think of in a few minutes sitting here having my first cup. Also some of these will cause a lean condition, but will cause a bog just the same):

Float level too low. Float too heavy from soaking up gas. Wrong float.

Needle and seat sticking or bad. Be sure you didn't hook the needle hook through one of the holes in the float arm- it is supposed to go on the back of the float cross piece, closest to the PP well.

Power piston stuck full rich or way too strong spring or wrong length spring for your PP.

Primary jetting way to rich- jets too big and/or rods too small. Late rods in early carb casting (rods will be too short).

APT set way too high. What did you set it at, or did you leave it alone from where it was originally?

Plugged air bleeds. Missing, plugged fuel tubes in air horn. Tubes driven in too far. Tubes that are missing altogether or that have fallen out into the fuel bowl.

Secondary air valve spring tension too loose.

Secondary pull off bad.

Secondary rods too small. (See THIS thread for more on that).

If the castings are warped, wrong gaskets, mismatched parts, etc. they can be the cause of all sorts of problems.

I already mentioned the choke being on and the ignition timing. If the timing is off or the ignition system faulty, it can run for ****, too.
10-22-2011 09:26 PM
69chevyLWB Cobalt327
thanks for all the help!
it has a brand new distributor in it and the engine as been running before and i didnt change anything besides the carb. pcv is plumbed all plugs checked and distributor working fine. i think that is somthing i did wrong when i rebuilt it. it idles fine sometimes then others wont idle for crap. i have never been able to give it any amount of gas when i am driving or it just falls on its face. you can revv it to the moon when its just sitting in park but with any kind of load it just nosedives.
10-22-2011 08:29 PM
cobalt327
Quote:
Originally Posted by 69chevyLWB
I will have to try out the tip in method, forgot about that.
The secondaries have about 3/4 turn on them. There is two good streams coming out of the accelerator pump. i started it up again and it kind of surges and as a rough idle. i dont really know what to do. getting frustrated. on monday im gonna call Cliff and see what he thinks. not that you guys arent good help its just i bought the parts from him so maybe he'll have a better idea.
Double check the easy things first- the firing order (1-8-4-3-6-5-7-2) and be real sure #5 and #7 isn't swapped at the cap or at the plugs. The plugs should be fresh. Cap and rotor good, wires good. PCV connected and plumbed right.

Check closely for vacuum leaks and be sure of the timing. These are all things Cliff will no doubt also want you to double check, so that way you can eliminate them before calling.

Good luck.
10-22-2011 08:19 PM
69chevyLWB I will have to try out the tip in method, forgot about that.
The secondaries have about 3/4 turn on them. There is two good streams coming out of the accelerator pump. i started it up again and it kind of surges and as a rough idle. i dont really know what to do. getting frustrated. on monday im gonna call Cliff and see what he thinks. not that you guys arent good help its just i bought the parts from him so maybe he'll have a better idea.
10-22-2011 07:51 PM
cobalt327
Quote:
Originally Posted by 69chevyLWB
UPDATE: It now idles fine. it was the fast idle cam you guys were right i just had to get my finger under there to release it. now when i took it for a test drive. if i give it any amount of gas it bogs out and almost dies. should i adjust my APT screw? the reason i have this on my 305 is just to test it out to make sure everything works. it will eventually be going on a built 355 sbc making around 400 hp. it has 71 jets in it right now. any help is aprecciated.
You can do Ruggles' "tip in" method for setting the APT. If you set it right for the 305 you'll need to reset it for the built 350, most likely.

Also, with the engine off check the accelerator pump shot top be sure you get two strong streams from the shooters as soon as the throttle is opened.

Be sure the choke isn't closing on you.

Be sure the secondary air valve isn't set too loose or it'll open too early and will bog.

Check the timing to see that you have enough initial. Even a stock 305 can stand 12. Hook the vacuum advance to manifold vacuum if it's not already. You'll have to lower the idle speed using the curb idle screw. Readjust the idle mixture screws and road test it safely.
10-22-2011 01:39 PM
TommyK The first step in diagnosing a carb problem is making sure your ignition system is properly set up and functioning. What is your initial timing?

In your original post you stated you were unsure how to set the idle mixture screws. Do you have a vacuum gauge? If so after you have the ignition sorted start with the idle mixture screws two full turns out and then with the vacuum gauge hooked up adjust the screws out in quarter turn increments until you have achieved the highest vacuum reading. If the vacuum reading goes down or is unchanged try adjusting the screws in using the same procedure to find highest vacuum reading.
10-22-2011 11:55 AM
69chevyLWB UPDATE: It now idles fine. it was the fast idle cam you guys were right i just had to get my finger under there to release it. now when i took it for a test drive. if i give it any amount of gas it bogs out and almost dies. should i adjust my APT screw? the reason i have this on my 305 is just to test it out to make sure everything works. it will eventually be going on a built 355 sbc making around 400 hp. it has 71 jets in it right now. any help is aprecciated.
10-22-2011 10:35 AM
69chevyLWB All the gaskets were ordered from Cliff Ruggles by carb number. I will have to try the vacuum hose plugging and such. My dad thought it may be a bad shaft too so we sprayed carb cleaner and ether and even wd40 around them and got not change in idle speed so we dont think that could be it. The secondaries are 100% closed and i do have the secondary stop on and it is working.
10-22-2011 05:23 AM
TommyK Worn throttle shaft bushings can also be a source of unwanted idle air. A warped base plate can do it to.
10-22-2011 03:38 AM
cobalt327
A couple things to try...

Quote:
Originally Posted by 69chevyLWB
Okay i looked it all over again. and this is what i found: the primaries are closed fully but it still will not idle down past 1000. the fast idle cam is freee and not preventing movement so it is not that.
If the primary throttle blades are all the way closed and the idle is still too high, the idle screw can be moved back out once the problem is found, so that you have idle speed control. If it's not touching now, it's only because something else is causing the idle speed to be too high.

A vacuum leak can cause a too-high idle. Try removing the vacuum lines one at a time and plugging the port at the carb and see if you find one that will drop the idle speed down when it's removed and the port in the carb plugged. There are also vacuum ports on most intake manifolds- do the same to them.

Did this particular carb EVER work right? If it did, the gaskets that were used at rebuild may have been the wrong ones, or if you don't know what the carb was like before being rebuilt, it may have already had the wrong gaskets in it and if you replaced them exactly, you recreated the original problem.

Look to see that the secondary throttle blades are not hanging open. Some Q-jets have a link that locks the secondaries from opening when the choke is closed. If yours has this link be sure it will work to keep the secondaries closed- this will show you the secondary throttle shaft is fully closed. Be sure the sec. shaft isn't twisted, allowing one blade to be open while the other is closed.
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