Freshly rebuilt quadrajet flooding from top of carb

[Tarrcamp92]

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

[Cliff Ruggles]

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

[Tarrcamp92]

Okay I will look into that thanks for the help!

[daveqjet]

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.

[gregcarter]

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

[Cliff Ruggles]

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

[gregcarter]

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

[Cliff Ruggles]

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!

[gregcarter]

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

[gregcarter]

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

[gregcarter]

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

[gregcarter]

Better cam specs are 1500-4000\t270 280\t204 214\t.420 .443\t107Deg 117Deg\tB

G. Carter

[Cliff Ruggles]

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

[gregcarter]

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

[Cliff Ruggles]

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