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Discussion Starter · #1 ·
i'm thinking of just getting a holley 4175, not because i don't like quadrajets, but because i don't have time to dork around with a q-jet.

Anyways, what recently happened, after running ok is now i have no idle and i'm getting flooding.

The only thing i did was to adjust the secondary throttle plates to open more (the plates, NOT the air flap doors) and then did some "spirited testing" let's just say.... The jeg's reman q-jet shipped with the secondary plates really not opening at all. i got them to open about 30-40 degrees which is enough for now. i did this Monday night.

So, Tuesday morning, immediately after doing an acceleration test, i immediately noticed that the low speed and idle wasn't normal/as smooth as before. After work, i did another "test." After highway cruising about 15-20 mins came to a stoplight. Engine was really idling rough at this point. Then, at this stoplight, did another "test." After this is when the stalling/no idle/flooding happened at the next stoplight. This was Tuesday and before this everything ran fine.

-----timing very advanced but don't think this is the problem.

---- Choke works fine

---- fuel pressure last time i checked was about 5.5 lbs at idle. As soon as i open throttle it goes down to about 2.5-3.5.

---- "Normal" WAS 1000rpm neutral, 600rpm in gear. Won't do any of that anymore. If i put it in neutral and keep my foot on it i can get it to idle 800+rpm all day, as soon as i let up it putters out.

So to Sum: Engine will no longer idle and getting flooding. Ran good until immediately after adjusting the secondary throttle plates to open more and after doing acceleration tests.
 

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First off, buying a rebuilt is hit and miss. I've fixed plenty of rebuilt and recalibrated Qjets from reputable builders that had a lot of problems with them. Did you remove the carb to adjust the secondary throttle plates? Did you turn the carb upside down? If you did the needle might have dislodged in the seat. When it is idling look down the carb throat and see if fuel is spilling into the engine.
 

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Discussion Starter · #5 ·
1) yes, reman carbs SUCK, as i now realize, but that's another topic.

2) No, i did not take the carb off the engine to adjust the secondary opening; i used needle nose pliers to bend the contact tab from the primary throttle arm which contacts the secondary throttle linkage. Can post a pic if necessary.

i'm now leaning towards the secondary plates not closing completely. What else could it be? Because that's the only thing that was changed?
 

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Picture would be helpful..
Needle & seat leaking , PRI. Power valve sticking , metering rods sticking , bent , secondary air flaps not closing leaving sec metering rods up , sec throttle blades not closing ...
 

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I went thru a Q-jet for a 69 BBC Corvette that our friend was having issues with. It was a purchased rebuild from some Corvette jobber. As it turns out it was a combination of different carbs. The piston didn’t even contact the cylinder walls. Meter rods were wong. I was able to come up with correct pieces required. As a result of the mismatched parts the wrong main gasket was also used also contributing to the issues. Holes and oriface‘s didn’t match up. Once correct parts and gasket were assembled it’s running fine.

So from this one experience would I ever seek a commercial rebuild carburetor from who knows were? No definite no.
 

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This is kind of a double blind test. While adjusting the pull rod so the secondaries are fully open with the primaries,,,, you also have to check that they fully close.

Bogie
 

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1) yes, reman carbs SUCK, as i now realize, but that's another topic.

2) No, i did not take the carb off the engine to adjust the secondary opening; i used needle nose pliers to bend the contact tab from the primary throttle arm which contacts the secondary throttle linkage. Can post a pic if necessary.

i'm now leaning towards the secondary plates not closing completely. What else could it be? Because that's the only thing that was changed?
I think you answered your own question.
Other possibility is trash in the needle.
 

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Discussion Starter · #10 ·
The secondaries do close, so i'm baffled at this point.

i will try trash in the needle+seat (and i doubt that is the problem either) next.

It really can only be like 4 things. The idle tubes couldn't have gotten clogged that fast from monday night to tuesday morning?
 

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Discussion Starter · #11 ·
Power valve and primary needles move freely---tested thru the vent.

Float was 12/32 per spec, i even lowered it to 18/32 (ok per specs) and no change.

i am happy, and surprised at the increased performance with the secondaries, but that's not important now----if i can't get it to idle and re-start.....
 

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If it's flooding, then fuel level is too high, or air bleeds are clogged. Check float to see if it's gone bad suddenly. Give it a aerosol overhaul and blow out the bleeds and pull the idle screws and blow car cleaner through the screw holes
 

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Discussion Starter · #14 ·
i think i found it: The choke wasn't opening; The plastic plug part broke off and i was just using the metal clip part----not the right way to do it. i may have jarred it when adjusting the secondaries OR extra vibration from the spirited testing may have moved it. So that's likely why the symptoms suddenly happened after monday night...?

Apparently an engine can run rich at higher rpms, not so well under 800rpm?

How stupid can you get.....

Sorry for wasting everyone's time.

i will order a proper plug end from Summit and do it the right way.
 

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No need to be sorry, it all got you looking around, I assumed, as everyone else I suspect that the choke was OK giver you were in there. I been through more than one rain dance only to find it was something simple stupid that got overlooked.

Bogie
 

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First off, buying a rebuilt is hit and miss. I've fixed plenty of rebuilt and recalibrated Qjets from reputable builders that had a lot of problems with them. Did you remove the carb to adjust the secondary throttle plates? Did you turn the carb upside down? If you did the needle might have dislodged in the seat. When it is idling look down the carb throat and see if fuel is spilling into the engine.
If the little arm behind the choke linkage doesn’t drop down when the choke opens all the way then the secondaries won’t open Quadrajet carbs are designed to not allow the secondaries at all until the choke is fully open. I’m concerned that your understanding of a Quadrajet is too limited for you to be making adjustments. I’ve been running Quadrajet carbs since 1971 and have always enjoyed success in the operation of them. There is a sequence of 14 critical adjustments to be made when rebuilding a Quadrajet. If everything is done right they will give you many years of trouble free operation. I ran one on my 78 K-10 for 16 trouble free years and it was still flawless when I traded the truck. Sorry to hear that you took such drastic measures with yours. Suspect that the secondary throttle plates are no longer closing tightly.
 

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i think i found it: The choke wasn't opening; The plastic plug part broke off and i was just using the metal clip part----not the right way to do it. i may have jarred it when adjusting the secondaries OR extra vibration from the spirited testing may have moved it. So that's likely why the symptoms suddenly happened after monday night...?

Apparently an engine can run rich at higher rpms, not so well under 800rpm?

How stupid can you get.....

Sorry for wasting everyone's time.

i will order a proper plug end from Summit and do it the right way.
As I mentioned in my extended response. The choke must open completely for the secondaries to open. If you have tried to defeat this feature by bending the linkage, try your best to restore the bends to original. Then pursue getting the choke fully operational including making sure that the little weighted arm in the choke linkage drops down when the choke is full open. This is necessary for the secondaries to open.
 

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Discussion Starter · #18 · (Edited)
If the little arm behind the choke linkage doesn’t drop down when the choke opens all the way then the secondaries won’t open Quadrajet carbs are designed to not allow the secondaries at all until the choke is fully open. I’m concerned that your understanding of a Quadrajet is too limited for you to be making adjustments. I’ve been running Quadrajet carbs since 1971 and have always enjoyed success in the operation of them. There is a sequence of 14 critical adjustments to be made when rebuilding a Quadrajet. If everything is done right they will give you many years of trouble free operation. I ran one on my 78 K-10 for 16 trouble free years and it was still flawless when I traded the truck. Sorry to hear that you took such drastic measures with yours. Suspect that the secondary throttle plates are no longer closing tightly.
UPDATE:
You got that right; The choke had nothing to do with it----it's still doing it even after i fixed the choke not working.

By "It," i mean it seems to be running rich and i can't keep it running under 1000rpm---can only keep it running by juicing the throttle with my foot. Visually the carb seems to be leaking around the air horn/top cover, the accelerator pump shaft hole, and other areas where the throttle body meets with the base plate. The top gasket seemed very wet, but i hear that's normal?


i did some "testing" last night:

1) i turned on the electric pump ONLY but didn't run the engine for a few mins. It did not appear to flood or leak. i then pushed down on the float with a thin ruler thru that slot and when i did so you could hear a drastic change in tone of the pump; That's when i did notice some fuel coming out of the accel pump shaft hole. Let up on the float, pump goes back to "clicking" and no more fuel seeping out. So, i suspect that the float, needle and seat are ok? While acknowledging this test alone may not mean they are ok.

a) i don't know if mentioned this before but it's a Jeg's reman Q-jet. #15005(which i feel may be a POS). The instructions say it can't take more than 5psi fuel pressure (even though general consensus seems to be 6.5-7lbs.?) The last time i measured fuel pressure i believe i got 5.5lbs at idle.
So this may be another thing to check?

2) i then ran the engine with no throttle intervention and just stood to the side and observed. Choke started to open, rpms went down and it puttered out.
The carb, both inside and out seemed "wet." Obvious leakage all around, maybe not major, but noticeable. There seemed to be fuel on top of the primary blades and even a little on the secondary blades. The "fuel module"---part where the idle tubes are and above the "accelerator pump squirters" seemed noticeably wet with fuel.

i think it's best to take a picture.



i WILL figure this out. Not necessarily against rebuilding just don't think i have time right now, but i haven't ruled that out either.

One problem i've been noticing though is that :

a) Reman q-jets (and this is not necessarily my first choice either...) seem to be having a supply/availability problem.

By reman, i mean the next step up remans----jegs and summit. As opposed to the atrocious auto parts store remans.
Neither of these choices are that good although i feel the jegs and summit remans are a little better.....

b) i mentioned the holley 4175 (which might actually be a better choice for me as, yes, my carb knowledge isn't that good and the holley is simpler, plus i can start off with a brand new carb) Well, they too seem to be having an availability issue as well; Looks like that they have to make a few as they can't ship for 2-4 weeks.

c) The reputable q-jet remanufacturers, i.e., Cliff Ruggles etc. are backed up.

So, i think what may be happening is that unfortunately the quadrajet's popularity is waning even more. Really ALL carbs, but especially the quadrajet. The advent of the bolt on EFI kits is not helping the situation at all.

So, i suspect sales are down and if they're down, why carry it? The quadrajet seems to be waning even more which is sad and strange considering how many millions of these gm put on cars and trucks.


i AM resolved and committed to figuring this out. i don't feel i have a choice....
 

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Discussion Starter · #19 ·
As I mentioned in my extended response. The choke must open completely for the secondaries to open. If you have tried to defeat this feature by bending the linkage, try your best to restore the bends to original. Then pursue getting the choke fully operational including making sure that the little weighted arm in the choke linkage drops down when the choke is full open. This is necessary for the secondaries to open.
i do understand about the choke lockout tab for the secondaries. Now that i think about it, the choke MUST have been working saturday night because i would not have been able to open the secondaries (i could definitely tell they were opening up). No, i didn't try to override this tab.

Also, visually the secondaries seem to be closing all the way. i acknowledge that visually does not necessarily mean they ARE closing all the way. But they appear to be that they are closing all the way.
 

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Discussion Starter · #20 ·
Another problem in addition to the ones i listed above is since q-jets haven't been produced for 30-40 years, we only have salvage yard cores or other sources for original cores, such as sitting on someone's shelf. The reman cores have, for the most part, been ruined.

At least with holley you can get a 100% brand new carb----well, if they would carry them; i think holley too realizes the demand for spread bores is dropping......

One source for a good core that hasn't been snatched up yet MIGHT be the 4.3 262cid v-6 q-jet. i think this one is actually rated at 850cfm. These seem plentiful in salvage yards. The trucks, astro and full sized vans had these for two years.
 
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