unjunking the quadrajunk

[thecantaloupeman]

So I am finally getting around to fixing my carburetor issue. I have traced a number of issues to being possible carb related things and decided to figure out what I'm gonna do about it.

So I had a breakdown a while back and assumed it was ignition components so I swapped it all out. I never broke down again, but I still had a remnant of a similar issue driving around in the cold.

Until the engine was all the way up to operating temperature especially in the cold, slowly applying throttle caused a sputter. I was still able to drive but it was a minor annoyance and I never figured it out. I'm thinking maybe the carb was the real culprit.

I've had a few rough starts when the engine was still warm and it never used to do that. It used to just start right up. I'm wondering now if the float is getting stuck occasionally. If I hold my throttle right at the beginning of the pedal travel it almost stalls itself and sometimes does. I felt like the problem was mostly gone until I replaced the muffler and tailpipe. I had it on straight pipe for a while and thats when it seemed pretty noticeable.

Today I got the muffler welded in and now it is all finished, but on the drive home, the engine almost felt stuck at a higher RPM. I had a hard time braking at a light and then noticed it was idling super high. I felt like it wanted to take off. It was running really rough and was emitting some black smoke out the tailpipe.

I called the exhaust shop and he figured my carb needed adjusting since there was now back pressure. (Old exhuast system had holes). Few hours later I started it up and it seemed fine moving it into the garage. I adjusted the carb and drove it about 15 mins and had no issue. I don't really know if what I did solved the problem or if it solved itself.

Bought some parts from a guy today and he reckoned my float was getting stuck, which sorta made me relate it back to my other issues. Do you guys think it was just the new exhaust or was it a coincidence that it happened at the same time and was really the float?


I was thinking about just saying screw it and getting either a holley or edelbrock. He had a nice deal on an older holley and manifold and also had some other quadrajets. He also offered me an edelbrock performer aluminum intake for 60$.

If I go the holley route i could buy everything in one place and then rebuild it on my own time in the quarantine. I've read holleys aren't reliable and not great for the street, but are they easier to rebuild/set up right than a quadrajet/edelbrock? I am honestly just done with the carb thats on my truck. The previous owner rebuilt it, but must not have done a great job.

 

[AuroraGirl]

So I am finally getting around to fixing my carburetor issue. I have traced a number of issues to being possible carb related things and decided to figure out what I'm gonna do about it.

So I had a breakdown a while back and assumed it was ignition components so I swapped it all out. I never broke down again, but I still had a remnant of a similar issue driving around in the cold.

Until the engine was all the way up to operating temperature especially in the cold, slowly applying throttle caused a sputter. I was still able to drive but it was a minor annoyance and I never figured it out. I'm thinking maybe the carb was the real culprit.

I've had a few rough starts when the engine was still warm and it never used to do that. It used to just start right up. I'm wondering now if the float is getting stuck occasionally. If I hold my throttle right at the beginning of the pedal travel it almost stalls itself and sometimes does. I felt like the problem was mostly gone until I replaced the muffler and tailpipe. I had it on straight pipe for a while and thats when it seemed pretty noticeable.

Today I got the muffler welded in and now it is all finished, but on the drive home, the engine almost felt stuck at a higher RPM. I had a hard time braking at a light and then noticed it was idling super high. I felt like it wanted to take off. It was running really rough and was emitting some black smoke out the tailpipe.

I called the exhaust shop and he figured my carb needed adjusting since there was now back pressure. (Old exhuast system had holes). Few hours later I started it up and it seemed fine moving it into the garage. I adjusted the carb and drove it about 15 mins and had no issue. I don't really know if what I did solved the problem or if it solved itself.

Bought some parts from a guy today and he reckoned my float was getting stuck, which sorta made me relate it back to my other issues. Do you guys think it was just the new exhaust or was it a coincidence that it happened at the same time and was really the float?


I was thinking about just saying screw it and getting either a holley or edelbrock. He had a nice deal on an older holley and manifold and also had some other quadrajets. He also offered me an edelbrock performer aluminum intake for 60$.

If I go the holley route i could buy everything in one place and then rebuild it on my own time in the quarantine. I've read holleys aren't reliable and not great for the street, but are they easier to rebuild/set up right than a quadrajet/edelbrock? I am honestly just done with the carb thats on my truck. The previous owner rebuilt it, but must not have done a great job.

It could just be an issue of age and ethanol. If you can get the intake for 60... thats a good deal, even with stock carb its just a good deal, id snag it. But if you dont want to break the bank, you could do what some other guys recommended to me and have it sent out and rebuilt, the turn around wasnt too bad. maybe make sure the covid thing isnt causing them delays. that would be the second-cheapest and easiest method I would think, since you dont have to replace the intake and do gaskets. but it does sound like something was sticking and it happened to unstick. prob will again.

 

[1987 GMC Jimmy]

Unless the carburetor body is warped from improper or overtorquing, there’s nothing wrong with the carb. It sounds a little bit like heat soak induced fuel boiling/vapor lock, although more information would be needed to draw that conclusion, so a return style pump with return senders would help you if you don’t have them already. That’s big picture, though.

It likely wouldn’t hurt to rebuild the carb, and it would be pretty easy to either do that yourself or have someone do it locally. You could send it off, but an M4M carb like that is pretty universal. What I’d like to see is that the accelerator pump linkage is tight relative to the accelerator lever and gasoline is squirting into the throat of the carb as soon as that piston starts to move and as long as it’s moving. You also need to make sure choke operation is correct to rule that out. Float adjustment would have been more in play if it had always acted up, but a sticking float can’t be ruled out.

If you want to wash your hands of it, you can always mail it out to someone who’ll rebuild it for you, address the well plugs, put a primary throttle shaft bushing in, etc. You’re looking at about $200-$250 for that.

 

[HotRodPC]

Rough starts when the engine is still warm is usually the leaking well plugs. Fuel drips into the intake and vaporizes on the hot floor of the intake and vapor locks in bad cases, or makes starting tough at least. Other issues can be vacuum leaks at the throttle shaft. You get a good Qjet builder where he seals the well plugs and bushes the throttle shafts with brass bushings, thet thing will last about forever and then when it does need a kit, it's a sucessful fix unlike most who put kits in Qjets and never fix the well plugs and leaking throttle shafts so they don't see or feel the huge gain of a carb rebuild.

 

[broketiredugly]

i used to have a little hammer just for q-jet rebuilds. tap the plugs and reseal them. agree with everything said above. but i would also adress the needle and needle wear.

i wouldnt listen to whoever told you holley are not reliable. they are very reliable, easy to maintain and parts/mods are readily available. the biggest problem is wrong carb choice per application, and other modifications that affect and / prevent the ability to tune. wrong cam selection, wrong exhaust tune, etc: and you have an engine that cannot be tuned, so they buy a shiny new carter afb clone and bolt it down. they justify the poor choices by saying things like "its got a mean lope". lol

 

[Paladin]

2 step solution:

Step 1: place QuadraJUNK into a rockcrusher......

Step 2: get a HOLLEY.......

Problem solved....

 

[82sbshortbed]

I got a Quadrajet level 2 from national carburetor last year I'm getting rid of for $200 plus shipping(about $20)if you don't wanna mess with it. Just let me know.

It's ready to slap on and fire up. It was working great but, I just put in a BBC 454 and don't need it now.

 

[1987 GMC Jimmy]

Yeah, whoever told you Holley was bad is an idiot. They’ve been making carburetors for about 120 years so I think they’ve had plenty of practice. Same thing for other Holley/Weiand performance parts. I would say the same in principle for Edelbrock intakes, but they’re just building Carter AVSs/AFBs and slapping that red logo on them. Meh.

Holley knows how to build a carb for different applications, just look at the difference between an Economaster and a 750 Double Pumper. It’s not the same approach as the Quadrajet, one size fits all, but purpose building them is an equally valuable approach. This might be controversial, but Edelbrock uses old Carter designs, which are more primitive than anything commercially available, and it’s really just a shiny, American Graffiti carburetor. They work, they’re simple, and they’re easy to adjust if you need, but the reason I like the Quadrajet so much is because it’s been the most technologically advanced option for the past 55 years with maybe the exception of a Carter Thermoquad, but the Q-Jet is physically more robust. They’re still simple, but I’d like them to be able to meet different challenges adequately. If I didn’t care about metering and just wanted gas to be sucked through a hole, I’d drive a lawnmower everywhere.

 

[thecantaloupeman]

Yeah, whoever told you Holley was bad is an idiot. They’ve been making carburetors for about 120 years so I think they’ve had plenty of practice. Same thing for other Holley/Weiand performance parts. I would say the same in principle for Edelbrock intakes, but they’re just building Carter AVSs/AFBs and slapping that red logo on them. Meh.

Holley knows how to build a carb for different applications, just look at the difference between an Economaster and a 750 Double Pumper. It’s not the same approach as the Quadrajet, one size fits all, but purpose building them is an equally valuable approach. This might be controversial, but Edelbrock uses old Carter designs, which are more primitive than anything commercially available, and it’s really just a shiny, American Graffiti carburetor. They work, they’re simple, and they’re easy to adjust if you need, but the reason I like the Quadrajet so much is because it’s been the most technologically advanced option for the past 55 years with maybe the exception of a Carter Thermoquad, but the Q-Jet is physically more robust. They’re still simple, but I’d like them to be able to meet different challenges adequately. If I didn’t care about metering and just wanted gas to be sucked through a hole, I’d drive a lawnmower everywhere.

Actually I may have discovered part of my issue. My choke lever c clip is gone and the choke wasn’t moving. I think some other parts of the choke might be broken too so I’ll include pics. I am going to have to figure out how to adjust the choke on mine and maybe that will fix the issue.

The first pic shows the hot air lever and the c clip. It looks like there is an oval shape instead of a circle where that rod connects. It basically allows for play and when the rod comes up it doesn’t actuate anything until it gets farther up. Not sure if that is how it is supposed to be or not.

The second picture shows what I think is the fast idle cam. I was messing around and it moved and sort of “popped” into a lower position and moved the whole throttle assembly and choke and I felt like I broke something. It kept moving up and down and didn’t feel smooth. It felt like it was getting stuck in certain spots I’m really hoping I didn’t break this. I don’t know how it works.

The last picture shows my missing c clip so I’m gonna be on the hunt for a new one. Hoping it didn’t fall into the carb. But it must’ve been gone a while and I didn’t have a choke and didn’t notice. Which surely must’ve been causing a lot of problems.

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[HotRodPC]

Those bi metal spring choke stoves are know to go with age too. You may want to watch it on a cold morning and be sure it's pulling enough.

 

[SirRobyn0]

Do you guys think it was just the new exhaust or was it a coincidence that it happened at the same time and was really the float?


I was thinking about just saying screw it and getting either a holley or edelbrock. He had a nice deal on an older holley and manifold and also had some other quadrajets. He also offered me an edelbrock performer aluminum intake for 60$.

If I go the holley route i could buy everything in one place and then rebuild it on my own time in the quarantine. I've read holleys aren't reliable and not great for the street, but are they easier to rebuild/set up right than a quadrajet/edelbrock? I am honestly just done with the carb thats on my truck. The previous owner rebuilt it, but must not have done a great job.

I think it is coincidence and has nothing to do with the exhaust work. Were it comes to after market carburetors I prefer Edelbrock to Holley, but they all have their pluses and minuses. Keep in mind if you purchase an aftermarket carburetor you will need install the appropriate intake or adapter, and adapter for the throttle linkage, if you have the 700R4 you'll need a geometry correction kit. There is quite a bit of work involved in changing carb types properly. The Q-jet when in good shape can be a really great carb ust because yours is having issues doesn't make them all bad.

From what you have said in this thread and in previous threads I believe you have some internal issues, possibly a plugged circuit in the carb, possible float issues, getting the choke working right though would be a good first step.

Rough starts when the engine is still warm is usually the leaking well plugs. Fuel drips into the intake and vaporizes on the hot floor of the intake and vapor locks in bad cases, or makes starting tough at least. Other issues can be vacuum leaks at the throttle shaft. You get a good Qjet builder where he seals the well plugs and bushes the throttle shafts with brass bushings, thet thing will last about forever and then when it does need a kit, it's a sucessful fix unlike most who put kits in Qjets and never fix the well plugs and leaking throttle shafts so they don't see or feel the huge gain of a carb rebuild.

I'll second HotRodPC's remarks.

I got a Quadrajet level 2 from national carburetor last year I'm getting rid of for $200 plus shipping(about $20)if you don't wanna mess with it. Just let me know.

It's ready to slap on and fire up. It was working great but, I just put in a BBC 454 and don't need it now.

Though I still rebuild carbs at the shop, if for some reason there is one we just can't bring back we get our replacement units from national. They are a great company, I'd highly advise a National rebuild over whatever junk the parts store sells.

 

[HotRodPC]

Though I still rebuild carbs at the shop, if for some reason there is one we just can't bring back we get our replacement units from national. They are a great company, I'd highly advise a National rebuild over whatever junk the parts store sells.

I haven't seen him in a minute, and don't recall his name but we have a resident Qjet builder here that does them right with the proper mods and fixes. Not sure if he's cheaper than national and not sure if national requires a core. Our guy here, you ship him yours and he ships it back.

 

[1987 GMC Jimmy]

I haven't seen him in a minute, and don't recall his name but we have a resident Qjet builder here that does them right with the proper mods and fixes. Not sure if he's cheaper than national and not sure if national requires a core. Our guy here, you ship him yours and he ships it back.

You’re thinking about Quadrajet Power. I think he charges about $200 plus shipping for a standard rebuild. I used Mountain Man, and they were $200 plus shipping.

 

[HotRodPC]

You’re thinking about Quadrajet Power. I think he charges about $200 plus shipping for a standard rebuild. I used Mountain Man, and they were $200 plus shipping.

If shipping isn't to far out there, that's not bad really if he does the work he says he does and they look like new when you get it back. Nothing wrong with a QJet once you get those bugs fixed. They'll last about forever after that. You might have to put a kit in it every 8 -10 years to freshen it up, but once the well plugs are sealed and the throttle shafts are bushed, then even a caveman can clean it put a kit on one, replace the metering rods if he chooses.

The guys who can't seem to get one to tune is usually the throttle shafts leaking vacuum.

 

[SirRobyn0]

If shipping isn't to far out there, that's not bad really if he does the work he says he does and they look like new when you get it back. Nothing wrong with a QJet once you get those bugs fixed. They'll last about forever after that. You might have to put a kit in it every 8 -10 years to freshen it up, but once the well plugs are sealed and the throttle shafts are bushed, then even a caveman can clean it put a kit on one, replace the metering rods if he chooses.

The guys who can't seem to get one to tune is usually the throttle shafts leaking vacuum.

Former owner put an Edelbrock on my truck and it is fine and I'll keep it, but I wouldn't personally choose to do that. I've also got a 1977 Cadillac hearse, 425. Gets used mostly in October, often sits for more than 6 months at a time without being even started. It left the funeral home in the late 90's and since then has never has a rebuild on the Q-jet, don't know about before then though, but it still operates just fine.