Cliff's Quadrajet Parts and Rebuild Kits
Quadrajet Problem Solving => Dialing in your rebuilt Quadrajet carburetor => Topic started by: Tarrcamp92 on April 09, 2015, 10:55:03 PM
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Hi there. I'm pretty new at the carb stuff, so I just recently got my carb rebuilt put it on fired the car up started no problem but as soon as the car starts to run fuel starts spraying from the top of the carb and the car stalls, from what I've been reading I'm guessing the float is being the problem? Just wondering if anyone knows why it's doing that and what can I do to fix it? Thanks
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Float not holding down the needle or leak at the needle, or under the fuel inlet seat.
The upper portion of the hinge pin can get bent down and not keep the float in it's correct geometry.
Could also be a piece of debris stuck under the needle.
I've also seen scenarios where the carb will flood when the bowl fills up quickly and the incoming fuel holds the float down and woln't allow it to seat the needle. Usually you can just shut off the engine and wait a moment, then re-fire it and all will be fine.
The float and needle/seat set-up in the q-jet is a very simple design, and seldom gives troubles unless the float setting is incorrect, fuel pressure too high, or something is stuck under the needle. In rare cases the float arms may be bent enough to cause the float to "drag" on the sides of the bowl or the arms drag on the PP housing and cause flooding, but this would be pretty rare and should have been caught during the "rebuild"......Cliff
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Okay I will look into that thanks for the help!
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hi tarrcamp92,i just had a similar problem but not flooding as such but a filthy rich idle blowing black smoke and stalling if I didn't hold the power on with foot on brakes when stopped,my float had absorbed fuel and lost buoyancy,took me a while to figure it out,lucky I had a spare.
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My float expanded and stuck at the bottom of the float bowl every time I rebuilt my carb. I had to stick a bent pick down the vent and lift it. Then one day I woke up and realized it was no good after I almost got stranded 80 mile from home, and I chucked it.
No I didn't.... I shaved it down until it couldn't catch on the sides of the bowl. Then the next time I got a brass one and stuck that in there.
This is on an Edelbrock 1902 carb on a stock 350 in a truck. Since Edelbrock doesn't sell a brass one, I chucked that one out and got a phenolic one.
gc
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Always replace the float during a rebuild. The latest design nitrophyl floats are fine and will not swell up, or absorb fuel and sink.
Brass floats are horrible, they are not the correct weight, or as buoyant as the nitrophl floats. The also develop leaks at the soldered joints and sink.
We have had ZERO issues with the latest production stock type floats, in any type of fuel.....Cliff
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I forgot to mention that the Edelbrock tech was adamant about using 7/16ths float adjustment(.4375), which is lower than any spec I've seen in the book so far. Would you use that number?
The guy sounded a little young.....
G. Carter
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What is the carburetor number?
Why is a "tech" at Edelbrock involved with the deal?
They need to come here for training on q-jet stuff. They had LOTS of issues, and the same part number could show up with half a dozen different calibrations, and all of them needed help in one or more areas.
They do make EXCELLENT q-jets, once you get good parts in them and correctly calibrated. Their castings were very well made, and typically in better shape than q-jet cores that have been around nearly half a century at this point......Cliff
I attached a pic of what most Edelbrock 1910 pump seals look like when they show up here!
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This flooding occurred long ago, and the Edelbrock conversation was long before I found your website.
The carb is a 1902 Edelbrock version qjet.
I have been reading the book while waiting for my drill bits to get here.
I noticed that the specs and recommendations for the Edelbrock carbs are only for the 1910, which is a 850 cfm unit.
The 1902 is rated for 750 cfm, so I'm not sure the recipes relate to my carb.
I will measure everything up today, and get back to you with my engine and carb specs to see if need to change anything.
The original problem was stalling when stopping and real poor idle quality after rebuilding, so I guess I didn't clean out the idle circuits adequately. You mention that Edelbrock provided enlarged idle circuits, so we'll see if I need to increase anything here after I measure it.
I have disassembled the carb, drove one idle tube too far and bent it down in the shaft.
I made a small bend in a piece of music wire, and sharpened the tip, and stuck that down into the tube and was able to hook it and raise it up, and bend the tube from the top with a small screwdriver to help get it around the corner. It actually came out the adjacent larger hole. Took about 2 hours. (this was before I received the book)
Then I broke the heads off 4 screws on the plates before I read on the forum about the heating the locktite trick.
I made a small centerpunch and punched a hole in the offending screws from both sides, then drilled a .050 hole in just a little, adjusted the center if it look off by angling the shaft and drilling a little deeper before drilling all the way thru.
Then I went to a .065 and then a .070. Then I got a slightly larger bit, heated the shaft, drilled from the bottom, and the bit caught the small remaining piece of screw upon exiting almost every time.
I noticed that the airhorn and body are warped and am considering straightening them.
I actually sanded the airhorn almost flat before I read that the gasket would take care of the problem.
So now I have some plates to drill holes through to make the jig, but I haven't seen any info on heating while straightening if necessary.
I thought I'd heat the assembled jig and carb in the oven to 350 or so, and then tighten the straightening bolts.
Ok?
So now I'm going to rebush the baseplate with your kit I received.
I'm going to order .035 idle tubes for this unit to replace the old ones and get back to you for any modifications you recommend.
Thanks,
Greg Carter
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On the Edelbrock 1902, I just noticed that the secondary shafts are 3/8ths, not 5/16ths like the primary shafts. There is very slight front to back movement on the secondaries, so perhaps I should skip rear bushings?
Thanks,
G. Carter
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Ok, I measured the secondary slop, and it is about .010. Does that mean that I have to buy a 2nd drill and bushing set?
I installed the primary bushings today, and it feels good. A little snug at first, but after recleaning, sanding the shaft a little, and wd40, it is nice.
The air gap on the throttle plates didn't improve much, the front is tight on both sides near the idle openings and the back seems to touch a little before seeing a sliver of light, then opens up on all four sides a little. I suspect this is as good as it gets, but may indicate that the idle speed control screw had been backed out all the way for a period of time, slightly bending the front of the plates up by contacting the throttle bore.
I measured my tubes today and are as follows:
(as close as I can get it) all are original parts
Idle adjustment screw holes .081
idle tubes .032
idle channel restriction a .043 drill fit, a .052 did not
don't know where the inbetween bits are
main well bleed tubes .025
secondary well tubes .070
main jets .069
rods 36B
sec rods DR
This carb is on a '76 Chevy C-10 pickup with a stock 350 except for an "RV cam", Lift .420/.443, Duration 270/280, and an Edelbrock egr manifold (Calif).
One more thing.... The power valve only had about 1/8th" travel, I thought it had more years ago.. (My old Doug Roe book said it should be around a quarter inch travel.)
This model carb has a horizontal threaded screw between the idle screws, that adjusts the closed power valve height ( I've never touched it.)
I was unable to turn it in to get a base setting, and I had to heat up the area, and grab a small screwdriver with channel locks to rotate it out. It was all gummy in there, and it must have filled up the void and raised the valve. I suppose I'm looking for a beginning height setting, and can set it from there based on info in the book.
Thanks for any help and encouragement you can give me,,
G. Carter
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Better cam specs are 1500-4000\t270 280\t204 214\t.420 .443\t107Deg 117Deg\tB
G. Carter
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It is not necessary to install bushings in the secondary side, the clearance is needed so the huge secondary throttle plates can fully seat in the bores each time they close.
Nothing mentioned of idle and main airbleed sizes, those carbs came in many configurations. The APT system can be made externally adjustable, we sell an external screw for those.
If your 1902 is the single MAB model it will take a slightly different calibration than the four MAB design......Cliff
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I did some more measuring and reading and have more information for you.
idle tubes .032 (just bought .035 to replace these)
idle channel restriction a .043 drill fit, a .052 did not
don't know where the inbetween bits are
upper idle air bleed .068
lower idle air bleed .062
idle bypass air .039
mixture screw holes .081
main air bleeds (horn) .052
main air bleed (body .110
main well bleed tubes .025
secondary well tubes .070
main jets .069
rods 36B
sec rods DR
float 7/16ths
I was hoping you would either recommend or hold me off the dewarping process. Its probably warped a little over 1/8th".
Thanks ahead for your help.
Greg Carter
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You have one of the two main airbleed divorced choke models and they left out the lower MAB. Call the shop and order a pair of MAB's, they need to use four .046" MAB's to work like they are supposed to.
7/16" is too low for the float level in that carburetor, move it up to 1/4"......Cliff
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Thanks, I'll order them on Monday.
I suspect that since you didn't say that I should change anything else that I will not be changing any of the other components.
I also didn't mention that I'm looking for economy, so hopefully this setup will be adequate.
In many of the pictures in the book, I noticed a dam between the accelerator pump and the fuel bowl.
My unit does not seem to have one, it is just a big void. Is this common?
Thanks, G. Carter
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If you are having issues right after a "rebuild" I would install one of our kits as well. Then you will address all the components related to flooding, and get parts in there that will hold up in this new fuel......Cliff
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ok, I received the main air bleeds.
They appear to have a .126 od.
What size should the holes they fit into be?
The upper ones look fine, it's the lower ones that may be too small.
Thanks,
G. Carter
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They fit the airhorn and main casting on all models that used 4 main airbleeds.....Cliff
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Ok, I finally got this one back together, filled the floatbowl on the bench, installed it the truck, started right up, but I had to hold the choke almost closed to keep it going.
I let it warm up like this, thinking it would get better, opened the idle mixture screws out, thinking it would get better, raised the idle speed up, backed out the mixture screws some more, but it still ran lean, lean lean.
I closed the choke plate almost all the way, and the idle came way up, and smooth.
I shut it off to ponder the problem.
The original problem was stalling at stop signs, and a super lean idle. (not flooding after a rebuild, as this thread heading implies)
In the carb reconstruction, the idle tubes were replaced to .035.
The float was replaced and raised to .025, it had been at 7/16ths.
The power piston was stuck up with about 1/8th inch travel from a bunch of gummy stuff down around the adjustment screw.
This model PP (Edelbrock 1902) has a horizontal adjusting screw between the mixture screws.
When I set it up I turned the screw in until it just barely lifted the PP as a starting point, as I had no information on where to set it.
I suppose I could try raising it a little, to see if more fuel will get to the idle system, but I thought I read somewhere that jets and rods had nothing to do with the idle system.
The idle shaft was bushed.
The upper mabs were decreased to.042 from .052.
The lower mabs were increased to .042 from .110.
The carb body was dewarped, and the airhorn was sanded flatter than it was.
The body was filled with carb cleaner for 20 minutes, rinsed with water, blown out with air, then spray carb cleaner, and then air again.
So that's where I'm at.
I thought I would take a vacuum reading tomorrow, but I don't know what it should be for this setup.
I thought I would test for manifold leaks again to see if I missed any.
I also thought that perhaps the idle downtubes may not have been cleaned adequately as the carb cleaner never got in there, even though I sprayed and blew them out several times.
I appreciate the help and recommendations you've given me so far, and I'm looking forward to your response.
G. Carter
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That small cam in a 350 engine should produce good vacuum at idle and not need a lot of idle fuel from the carburetor. The specs listed look fine, if it doesn't work well it has a fundamental issue someplace.
I see this sort of thing quite a bit, as about 1/3rd of what we do here these days is working on carburetors that have just been rebuilt but don't work correctly......Cliff
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You're right, it has plenty of vacuum.
I removed the carb, made a plate with an air chuck to seal the top of the manifold.
I put about 20 psi in there and couldn't hear any leaks around the manifold with my stethoscope.
I made a smoker and dumped smoke into the manifold until a little drift came out a open valve cover.
I don't think its leaking anywhere.
The last time I had it running, I sealed off every hose fitting (vacuum source) from the carb, ran it at idle, it was very rough.
I closed the choke to get it to smooth out. Then I opened and closed the mixture screws while watching the a/f meter to see if the mixture screws were functioning. Well, they were, just fine as long as the airflow was reduced.
I'm going to open the carb up again, and see if there is any restriction anywhere in the idle system, and if not, I'm going to open up the idle tubes to .037, and the mixture holes to .085.
It baffles me how this carb worked for years on three different engines, but doesn't today. Something has changed. I want to believe it is something outside the carb, but I can't.
If you think I shouldn't do the above change, or have a better specification, please post me.
Thank you for your help,
G. Carter
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If it's lean at idle open up the idle tubes and the DCR's, that will put more fuel to the idle mixture screws.
An external APT screw would be a good idea as well, with a spring on it to hold it's setting.
You mentioned installing bushings, did you use our kit to do this?
Did you ever get one of our rebuild kits for the carb?.....Cliff
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Hi there. I'm pretty new at the carb stuff, so I just recently got my carb rebuilt put it on fired the car up started no problem but as soon as the car starts to run fuel starts spraying from the top of the carb and the car stalls, from what I've been reading I'm guessing the float is being the problem? Just wondering if anyone knows why it's doing that and what can I do to fix it? Thanks
Do you have a brass float? And if so did you drop it? If you answer yes too both questions I bet it cracked.
Just ask me how I know...ha! ;)
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NEVER use a brass float in a q-jet. The failure rate for all current production brass floats we've used (or attempted to use) here has been 100 percent.
The latest production closed cell nitrophyl floats are excellent, zero failures to date with any of them, and they have better fuel control than the brass ones.......Cliff
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Ok, I finally figured this one out, after basically remanufacturing the carb.
It was......... filthy, rusty, watery, dirty gasoline.
I tried to start it one day and it wouldn't, noticed that no fuel was coming out the fuel line.
I emptied the tank, rinsed with phosphoric acid, rinsed with alcohol, and then acetone.
Then put a liquid liner in it and a new sending unit where the water laden air was entering nightly.
All this was expensive and stupid because a new tank was $90. The chemicals and liner cost more.
I flushed the lines and installed a new inline filter and a second one in the carb.
Fired right up and never stalled again.
So thank you Mr. Rugles for the carb lesson, I think I probably can fix one correctly now.
G. Carter
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Good news!.....Cliff
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Ok,Its not over yet.......
Thought I had it running good but it still kind of stank at idle as it always did for 15 years. The a/f meter said rich at idle and cruise.
A little history......
This carb, an Edelbrock 1902, has 3 vacuum fittings on the baseplate.
The egr vacuum, the vapor canister, and the PCV lines.
This truck had a 6 cylinder motor in it stock.
When I converted it to a V8, I had a Rochester quad on it, and don't remember how I hooked up the PVC and vapor lines.
When I put the Edelbrock carb on it, I hooked both the PVC and vapor lines together with a T that was on the engine when I bought it. (per my mechanic partner)
The vapor line fitting was hooked up to the canister on a second fitting that opens a diaphragm that allows the vacuum from the manifold to suck out the trapped vapors in the canister.
It seems to me that the PVC line should go to PCV valve alone..
The vapor line should go to the cannister, and the diaphragm activator should just be teed into the same vapor line.
Can anyone direct me on this????
The richness need to be addressed.
I increased the idle tubes to .035 from .032 during the rebuilds.
Since its rich now, and probably always was, I should go back to .032s???
And since the idle mixture affects cruise, should I wait to change jets or rods?
I have:
main jets .069
rods 36B
in there now.
The main jets have been in and out many times and don't look so good.
I didn't mention that the idle screws do little, it still runs when all the way in.
I just ran the motor with the idle screws in all the way, and had high O2 (.950-990) readings.
When I backed them out the motor slowed down.
What do you suggest?
Thanks ahead,
G. Carter
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Correct, the PCV line should only be going to the PCV valve.....Cliff
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Ok, I went ahead and replaced the .035 idle tubes with the .032's you sent and the idle appears controllable.
I took the truck to get smog checked and the co levels were 4 times higher (super rich) than 2 years ago.
I had installed .042 lower mabs (there were no original lower mabs) and replaced the .052 upper mabs with .042s per your recommendation during the rebuild.
This is the only place I can think of that the richness was made.
In your recipes in the book, the smallest mabs are .070, so I'm not sure why .042 were specified.
Should I yank the lower mabs back out, or drill upper and lower mab pairs out to get some air into the main system.
If you do recommend drilling them out, what size would be good?
Thanks ahead,
Greg Carter
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Are you still using .036" primary metering rods?
Did you install an external APT screw in the baseplate?
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The Edelbrock 1902 comes with a horizontal adjusting screw between the idle mixture screws for the base adjustment for the APT.
The metering rods are .036, jets are .069.
Thanks,
Greg
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I may have mentioned before, that I set the APT screw to slightly raise the power valve because I had no base setting because there was a bunch of gooey stuff in there and the screw was very difficult to remove when disassembling.
I can push the power valve down when the engine is off, and I can feel that it is down at idle with a small piece of aluminum tubing.
G. Carter
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With .036" metering rods in .069" jets you are too rich and not going to have any control with the APT screw in the baseplate.
Edelbrock found themselves using that jet/rod combination because they left out the lower MAB's in the main casting on the production line.....Cliff
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I'm guessing I'll order .040 rods?, Do the .069 jets sound adequate?
G. Carter
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When you get time call the shop and I'll set you up with some metering rods that will work.....Cliff
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Thank you Cliff for the jet needles. I installed them and I will test the cruise mixture on the freeway on Monday.
Unfortunately my idle is still stinky rich with no adjustment on the idle screws. The more I think about it, the more I think that this carb has always had a super rich idle since I bought it.
I had changed to .035 idle tubes but went back to .032 after still having a rich stinky idle. By the way, your new .032 tube collars are .060, not .061 like the old collars, they slid right in and popped out when I blew air through the main jet.
Anyhow, running the motor at a low idle, maybe 500 rpm, I backed out the idle screw until it was loose, and rotated the primary shaft. it closed a little more, and the rpm dropped about 50 rpm but did not stall. I ran the mixture screws in and out, and watched my O2 sensor read over .9 volt the entire time.
In the forum, I saw a few ways to address this problem, looking for nozzle drip, wrong gasket etc. Well, I finally used a flashlight and saw a drip on the passenger side, about a 1 drop every ten seconds or so. The driver side was dry.
My O2 sensor is on the driver side, and it is a split manifold with no connection so the richness on the right side wouldn't show up on the meter. The drip is not the original problem of overrichness
I am going to check the bottom gasket tomorrow and see if the bypass holes line up.
In the mean time, I am hoping that Cliff can recommend opening up the bypass holes to a larger size, and what size?
Here are the current specs:
idle tubes .032
idle channel restriction a .043 drill fit, a .052 did not
don't know where the inbetween bits are
upper idle air bleed .070
lower idle air bleed .062
idle bypass air .039
mixture screw holes .081
main air bleeds (horn) .042
main air bleed (body) .042
main well bleed tubes .025
secondary well tubes .070
main jets .069
rods .042
sec rods DR
float 1/4 inch
Thanks ahead,
G. Carter
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Ok, I'm dumb. I just looked at the manifold and both sides of the manifold feed both sides of the motor, so my O2 sensor is picking up the drip.
I am going to check the bottom gasket tomorrow (no, it is not one of yours, and I'm sorry)and see if the bypass holes line up.
If the don't line up, ( I did check them last Friday night, but my eyes could have been tricking me. One hole lined up, the other, I'm not quite positive), I'll cut the gasket larger.
Thanks ahead,
G. Carter
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Probably ought to check the other gaskets as well. Doesn't sound like you ever got a kit from us, so they may not be the correct gaskets either.....Cliff
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You just sold me the top gasket last week, I have your accelerator pump, and needle and seat in there, as well as 4 mabs, 2 idle tubes, and a atp screw, and new bushings. The only thing I can think of that isn't yours is the base gasket, and the throttle body gasket, which looks like an excellent quality gasket, just possibly with a slightly offset hole.
gc
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Ok, I removed the throttle body and saw that full manifold vacuum was being applied to the bypass opening in the carb body from a cutout in the base gasket. Whoops......
You are correct once again. I need the right gasket. I better order your float as well, and any other part you can think of. The list of your parts I have is above on the previous post.
I'll call you in the morning.
Thanks for your help,
G. Carter
Edelbrock 1902
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Thanks for the gasket.
I should have ordered a base gasket as well, just to make sure it was right, as it looks like there are more than 1 style.
The one I used has a flat area at the front that covers but does not seal the area of the pcv vacuum inlet. My other base gasket is open in this area and seemed wrong.
The motor ran a lot better with the new throttle body gasket, but I still did not have mixture screw control.
I poked around the secondaries, stalling the motor just by tapping the air valve, so I thought there might be some unwanted vacuum in there, so I removed the throttle body and detected small particles of dirt holding the secodaries open slightly. (I drive on dirty construction sites).
I cleaned and reindexed the plates and reinstalled the carb, sealed the airbox and now have control with the mixture screws.
So off to the smog shop I go.
I'll let you know if it passes.
G. Carter
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Ain't over yet.
Drove the truck to work (50 miles), seemed like the idle was low, so I raised it up a little and the stink and rough running was back.
I turned in the idle screws all the way, the idle came up, it stank, so I drove it home.
I looked down the primary side and it was dripping, tapped the air valve and it stalled. Looked down the secondaries and they looked clean
I opened the air valves and secondary vaives and sprayed cleaner around, and started the motor.
Wouldn't run 'til I opened the idle screws, so I set them and lowered the idle.
Open the air valves all the way, and the idle stayed almost the same, I think it dropped a little.
The secondaries must not be sealing all the time.
They looked and felt perfect when I had them apart yesterday.
I'm detailing out my air intake system, I can't think of any other thing to do.
Gregory Carter
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Here's another dumb one.... the air filter was too short allowing dirty air over the top into the nice clean carb.
Took care of that and took it to the smog shop.
Failed on nox, probably carbon buildup, egr blocked(which it is) dirty catalytic converter, or running hot. I'll work on these.
The smog tech said he thought the carburetor was working fine, even though I was getting a little choked up on fumes in his small shop.
That's all for now.
G. Carter
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Took off the manifold, and cleaned the egr passage, reassembled it all, and took it to the smog shop and it passed finally.
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Good news!