What's new
CK5
Register an account today to become a member! Once signed in, you'll be able to participate on this site by adding your own topics and posts, as well as connect with other members.

maybe not quadrajet problems???

down4thakrown

down4thakrown

1/2 ton status
 Premium
GMOTM Winner
Joined
Aug 5, 2003
Posts
1,981
Reaction score
342
Location
flagstaff,az
ive asked every one i know and no know whats wrong. i got 64cc cast iron world product heads & aluminum intake. when set the needles at 2 turns out it seems to run rich and when i go from a stop and it shifts into 2nd it starts to feel like its runnin rich and misses.but the more i drive the less it does it. also when i screw them in all the way it still runs fine ive rebuilt this carb to many times to count.could this be do to bad spark??now i replaced carb with brand new holley rebuild and doesn't miss until i punch it the it sounds like it wants to die and backfires outta pipes and through the mid range it makes a blubbering noize /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/1zhelp.gif
 
Re: quadrajet problems

Not sure if you understand the carb nuances, but you do know that the mix screws are ONLY for idle, correct?

If you have problems outside of idle, then the mix screws aren't it. I'd be leaning more towards float problems.
 
Re: quadrajet problems

If it is still running with them turned in all the way, you have a vacuum leak.

Dan
 
Re: quadrajet problems

[ QUOTE ]
also when i screw them in all the way it still runs fine ive rebuilt this carb to many times to count.

[/ QUOTE ]

Like DD said , vacuum leak . Is it really old ? I replaced mine because it was leaking around the throttle shafts and didn't feel like bushing it yet ( gonna put it in my "new" project ) . Spray some carb cleaner around the base ( be extremely careful !! ) and see if it improves . After you find and plug the leak , retune and see if you can get it nice . Maybe even bring it by sometime /forums/images/graemlins/k5.gif /forums/images/graemlins/k5.gif
 
Re: quadrajet problems

yea its a pretty old carb i just replaced the cap and rotor now it runs worse and it misses everytime i take my foot off gas then press /forums/images/graemlins/angryfire.gif
ill try the carb cleaner
how do i adjust the float?
thx
 
Re: quadrajet problems

[ QUOTE ]
could i spray some carb cleaner around the carb when its runnin to see if its a vaccuum leak?
how cdo? i adjust the float

[/ QUOTE ]

Yes , if your careful , wd-40 will work too , but need some wiping off . Be careful.

And you need to pop off the top again to adjust the float , you just bend the bracket attached to the float . There are other adjustments inside that carb , but stick with the basics for now .

Also do a search on Quadrajets , you'll turn up some good sites and info /forums/images/graemlins/thumb.gif
 
Re: quadrajet problems

the little bracket as in the piece that hangs the little pointed thing with a black tip?
 
Re: quadrajet problems

http://dyeager535.topcities.com/CCCqjetdiagram.html
according to this diagram i have the lean mixture screw #226 tightend all the way down. you think this could be the problem??i think its the piece that stops the primarys goin any further down. the pin that goes through the hanger for the primary needle hits it so they dont go down any further. /forums/images/graemlins/dunno.gif
 
Re: quadrajet problems

Well if you're running rich at idle and when it upshifts, that doesn't sound like a vacuum leak to me, a vacuum leak should make it run lean not rich. Sounds to me more like the lean stop screw is adjusted to far up. Sounds to me like the power piston is sticking in it's bore or it's spring is getting weak (if you've elimated the usual suspects, ie float level, needle and seat problems, sticking choke). Could even be the lean stop adjustment screw for the power piston (located right in front of it) if it's up to high it won't let the metering rods far enough down into the jets. Other thing that can happen is the check ball on the acelerator pump doesn't seat all the way and the vacuum through the primary bores will pull fuel through the pump causing a rich condition that goes away with throttle.
 
Re: quadrajet problems

alright its still doin it but worse. it has a real bad miss off the line or anytime i take my foot off gas and reapply. i just did all the gaskets, the check ball, float etc....but whats wierd is when i totally advance the distributor it comes and goes. /forums/images/graemlins/angryfire.gif i tried moving the wires one spot over but then its to far advanced.and when i turn the screws all the way it changes a little unlike before i couldn't tell a differance.also when i punch it,it starts to back fire outta the pipes and misses real bad. somtimes the four barrels open but theres no power and it doesn't pull /forums/images/graemlins/dunno.gif could it be valves or timing chain stretch im outta ideas and patience help plz /forums/images/graemlins/1zhelp.gif
 
Re: quadrajet problems

Try another carb, if you have one or borrow one. I have a quadrajet that runs too rich even with the mixture screws all the way in, no matter what i did was no help. Took it off and problem solved. Also you might want to try a new coil, they will do strange things. I blew a muffler apart because of a bad coil and would barely run "sometimes"
Good luck
 
Re: quadrajet problems

After rebuilding my Qjet, I could completely seat the mixture screws and it wouldn't change the idle quality. The advice I got from a mechanic buddy was that there was crud in the idle circuit. I pulled the carb off and blew carb cleaner through every hole I could find. That solved the problem.

Maybe my experience will help. /forums/images/graemlins/dunno.gif

Idle mixture is for the idle only, but if it isn't set properly it will affect the transition from idle to power.
 
Re: quadrajet problems

Take carb off your '79 and put on your '77........
 
Re: quadrajet problems

It might be in the distributor,not the carb--it sounds like you may have a pick-up coil with a break in one of the wires,moving the distributor around may be making the wires contact better--check the ignition coil and module too,I've seen cracked coils cause intermittent problems like your describing--the module has a curcuit to increase the dwell after 2000 rpm that might have failed,but will still let it run,though poorly,check the advance weights(on an HEI only,computer comtrolled trucks have none) and make sure the pins they ride on arent all grooved,causing them to stick.Vacuum leaks are a possibilty too,as the other posts have stated.A compression test will spot any bad valves,or a vacuum gauge will help pinpiont any leaks,watch the gauge as you spray any suspected leaks--it will help locate a bad valve too,it will drop a few inches every time that cylinder with a bad valve fires. /forums/images/graemlins/crazy.gif
 
Re: quadrajet problems

the coil looked brand new when i pulled it but, ill take it off again and look at it better and while im at it i'll get it tested with the ignition module. im thinkin valves too. i'll do the compression check to make sure.
thx, this site rules /forums/images/graemlins/peace.gif
 
Re: quadrajet problems *79 silverado az*4 sale

please post this in the correct forum.
thank you
 
Re: quadrajet problems *79 silverado az*4 sale

[ QUOTE ]
i also got a truck for sale in az 79 3/4 ton 2wd silverado
has front end damage but, the windows still work, v8,quadrajet, 14blt ff w/ 410,oil cooler,th400, new ac lines just need charge, custom aluminum wheels, all emission stuff there looks like it has a new air pump and vaccum canister .runs sat for a while. great tow rig. 900$obo.
just goin to buy new engine and carb, rebuild the one thats in there and put it in /forums/images/graemlins/k5.gif 602 841 7533 daniel

[/ QUOTE ]

Wrong forum. /forums/images/graemlins/whistling.gif
 
Re: quadrajet problems *79 silverado az*4 sale

no $ to put in other forum /forums/images/graemlins/whistling.gif
 
maybe not quadrajet problems

now i replaced carb with brand new holley rebuild and doesn't miss until i punch it the it sounds like it wants to die and backfires outta pipes and through the mid range it makes a blubbering noize /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/1zhelp.gif /forums/images/graemlins/angryfire.gif /forums/images/graemlins/angryfire.gif
 
You must log in or register to reply here.

Latest Posts

Top Bottom