Quadrajet Tuning Question

[ReedZ]

Hey guys.

I\'ve been having some problems with my carburetor as of late. It\'s a 4bbl quadrajet on a pretty much stock 305. I\'ve been having trouble getting it to stay going in the morning. The high idle is working on it, but unless i keep my foot on the gas, it\'s been stalling on me. This has been going on for just the past couple of weeks. I tried adjusting the idle up slightly, but that didn\'t help. Doing that, just made it run on after shutting off the truck. Also not sure if my secondaries are working correctly. How far open should the secondaries be opening when you stomp on the gas? Mine are barely moving when i do it.

I\'ve got another quadrajet sitting on my shop bench, but the high idle doesn\'t work on it. So i don\'t want to put it on either. I\'m debating whether or not getting the one on my bench rebuilt and using it. I\'ve also been wondering if maybe buying a holley or something may be a better way to go. Or if my problem is a simple one and just requires a small adjustment, then I guess I\'d go that route.

I\'m not that knowledgable with carb\'s, so any input you guys have, or recommendations would be greatly appreciated.



Thanks

Geoff

[Scotty_S-15]

I\'d do the easy thing first, and spray some carb cleaner on the fast-idle linkage, it may not be coming around fully.

.......... Regarding the secondaries, chances are you\'ll never see the AVS part of the secondaries open, ever, in neutral. The actual mechanical throttle blades, below the AVS plate should open fully, but you can\'t see the plates, just the linkage. There is usually some interaction between the choke/fast idle linkage and the mechanical secondaries, like the choke comes off when the secondaries are opened, or, the secondaries won\'t open if the choke is on.

[Ryoung68]

A vacuum leak will cause low idle, so make sure everything (intake, carb,etc...) are tight.

[gdmclnh]

Agree with Scotty. Vacuum operated secondary top butterfly plates will only open slightly if at all in neutral. Is the actual choke flap closing enough. If it isn\'t then the high idle won\'t help much.

[ReedZ]

Thanks guys. I\'m going to get a can of carb cleaner at lunch time. I\'ll also check my choke to make sure it\'s closing some when in high idle.

As for vacuum leaks, i did check that, and i don\'t appear to have any.

Thanks for the information on the secondaries. I didn\'t know that they didn\'t open really in neutral. I personally try not to rev the engine in neutral anyways. It was just something that i noticed recently when playing with the throttle.



I\'ll let you know what i find out after i try what you\'ve suggested.



Cheers

Geoff

[ReedZ]

I went out for lunch and i pulled the air cleaner off and attempted the start the engine. It goes to high idle, but the choke doesn\'t close at all. This is new, as it used to close when i pumped the gas before starting. So i was wondering if this is what Scotty_S-15 meant when you said maye the high idle is sticking and not coming around fully. I went and got some carb cleaner, but didn\'t have time to clean the area at lunch. I\'ll do it as soon as I get home tonight. Hopefully this is the problem and the carb cleaner will fix it up



Thanks

[fasrnur]

Look on the the rh side of the carb and make sure that the likage for the choke, on the throttle plate is releasing. It\'s hard to explain and easier to show you. Sorry! Ask a carb shop if you have one in the area.



Jeff...

[ReedZ]

No worries, i know what you\'re talking about. I had a problem with that last year. I didn\'t get a chance to do anything last night, so it looks like it\'ll be tonight. I\'m going to clean all moving components on it and make sure all mech\'s are operating smoothly. I\'m hoping that should solve my problem.



Will let ya know.



Thanks again

Geoff

[ReedZ]

Well, I cleaned the carb all up last night, all the mechanisms are moving well and not sticking. I also cleaned the plates and choke. I then had to adjust the idle slightly. Seemed to be working well. Until this morning when i couldn\'t get it to stay going again. In order for me to keep it going, i had to keep the peddle pushed down halfway. I don\'t know if the choke is not closing or what. I didn\'t have time to play around with it this morning, as i was running late.

This thing pisses me off sometimes. I\'d like to find a new carb and just bolt on and go rather than having to fiddle with my current one all the time.

Guess i\'ll try to fix it again this Friday when i have time. Hopefully it won\'t be anything too major.

[Scotty_S-15]

Here\'s a wild stab. Maybe the choke pull-off is NG, and for the truck to run half way decent with the bad pull-off, the choke is set way too lean.

......... Basically, when you step on the pedal, the choke closes completely if it\'s cold enough. As soon as the engine fires, the choke blade needs to open somewhat, regardless of how cold it is. This is done by the vacuum operated pull-off. Meanwhile, the other choke linkage, including fast-idle remains as normal, slowly opening as the engine warms up.

.......... So as I said....... maybe the pull off is NG, and the choke has been set lean to compensate....

[ReedZ]

I hear what you\'re saying. I did check that also, when starting cold. I did notice the choke closes, but reopens when i fire it up. But i don\'t think it\'s opening quite far enough. If i manually pull it open just a smidge, it is fine.

I have decided though to get one of my other Quadrajets that i have rebuilt and i\'m going to put it on.

This may be a stupid question, but when you get a speed shop to rebuild a carb, I\'m assuming they typically tune it do they not? I\'m going to ask them of course when i take it in. Just thought i\'d ask the experts though first (You Guys)



Cheers

Geoff

[Ryoung68]

The Carb needs to be tuned to the specific engine so most Speed shops don\'t fully tune the carb for a basic rebuild unless requested by the customer.

[ReedZ]

Good to know.

I\'m taking the carb there at lunch time, so i\'ll talk to them about it and see what we can come up with.

[ReedZ]

Well, the bushings are shot on my carb and it needs a rebuild, so because it needs to have the bushings redone, the price is now double that of what it would have been. $350.00 cdn.

Is this price crazy? Or is this in line. Remember guys, Canuck Dollars here.

I\'m thinking i could just get a rebuilt 600cfm holley for that price. The guy also said not to use a holley with my 305, that i would get more performance out of the quadrajet with my 305.

Tell me what you guys think.