Need a Qjet Guru

[slammed79]

Hiya Folks.
    A few weeks back I rebuilt my quadrajet, even though it was "rebuilt" last year. The dude (who was a friend of mine) who rebuilt the carb, essentially did an exterior clean, and maybe adjusted the float. The carb started leaking between the baseplate and the bowl assembly. When I broke the carb open, it looked like it hadn't been touched in 10 years.

I bought a rebuild kit, new float and a choke pull-off from Napa, cleaned everything and put it back together.

Before the rebuild, I was getting roughly 11 in town. This is down from the 14 or so I was getting last year. I did add the steel 20"s and I discovered a fair amount of vacuum leaks caused by dried out hoses. Now, after the rebuild, I'm only pulling 8.5.

I must of messed up somewhere. Can anyone give me an idea of where to start looking?

[454Man]

Pics or carb #s would help a little. Did you adjust the Float?

[bd]

Assuming you didn't switch to the 20s at the same time you did the O/H and the timing is correct:

• wrong float, float level incorrect, or needle valve improperly 'hooked' to float
  
  
• power valve piston stuck, or rods not inserted into primary jets, or rods missing
  
  
• wrong bowl gasket installed
  
  
• warped bowl cover
  
  
• pull(s)/choke not correctly adjusted, or choke not opening
  
  
• leaking fuel well plugs or accelerator passage lead plug
  
  
• idle mixture screws set too rich
  
  
• air bleeds plugged
  
  
• vacuum hoses improperly routed/connected, or
  
  
• runs so well, your using all that extra power!   
  

[Fairlane514]

The primary throttle shaft is usually worn and loose and can cause a small vacuum leak.

[slammed79]

wrong float, float level incorrect, or needle valve improperly 'hooked' to float.

 I bought the float at the same time I bought the kit, and the clerk at Napa went off my carb number for the parts, so I'd hope I got the right stuff. I did set the float level, but that was the only part I was unsure of when I did the job. The carb # is 17058212. The stupid little clip on the needle valve was hooked on as I found it before.   

power valve piston stuck, or rods not inserted into primary jets, or rods missing

The metering rods are there and were set back into the jets. This was a bit of a pita after a couple adult beverages, but I got it done. Was moving well on reassembly.

wrong bowl gasket installed

I matched this up with the existing one. Thats not to say is it is in fact the correct piece, but it did seem to seat right, and looked correct.

warped bowl cover
Would this cause a massive drop in fuel mpg? I'm sure it'd cause a vacuum leak, but it seems like I got all those taken care of with the new hoses.

pull(s)/choke not correctly adjusted, or choke not opening
It seems to be doing its job, but it is late spring in AZ, so who knows if it is in fact working

leaking fuel well plugs or accelerator passage lead plug
What could cause that? I did blow out all the little nooks and crannys I saw before I reassembled.

idle mixture screws set too rich

I thought the same, and turned them back in to snug, then backed out two turns. They went in two and a half before they hit snug.


air bleeds plugged
Misc debris in there?

vacuum hoses improperly routed/connected
pics attached of the vacuum hoses , or

runs so well, your using all that extra power!

She's running real nice, just drinking gas like its a buck a gallon. lol

Pics



The egr is running into the port on the side, the pulloff to the lower, and that upper hose is going to the vacuum advance.


 

[rich weyand]

Vacuum advance is connected incorrectly.  You don't want it on "ported" vacuum, you want it on manifold vacuum.  Switch the vacuum advance to the lower vacuum port.  I'm not even sure looking at it that that is a vacuum port that you have it connected to.

See this pic.  You want a "non-ported" vacuum source for the advance.
http://www.gtoforum.com/attachments/f50/9784d1293232179-who-has-best-book-help-me-convert-quadrajet-img_20101224_163810.jpg

[bd]

wrong float, float level incorrect, or needle valve improperly 'hooked' to float...
I bought the float at the same time I bought the kit, and the clerk at Napa went off my carb number for the parts, so I'd hope I got the right stuff. I did set the float level, but that was the only part I was unsure of when I did the job. The carb # is 17058212. The stupid little clip on the needle valve was hooked on as I found it before.

Issues with the float/needle valve can cause it to run rich.  If the new and old floats appear the same, no worries.  If you're not sure of the float adjustment, however, recheck it!  High float setting can cause early tip-in of the main fuel nozzles and increase fuel consumption.  This is probably the most likely scenario.  Instructions and a gauge should have come with your kit.  The needle shouldn't be hooked into one of the 'holes' on the float, because that can interfere with needle valve function, causing it to hang open.


warped bowl cover...
Would this cause a massive drop in fuel mpg?  I'm sure it'd cause a vacuum leak, but it seems like I got all those taken care of with the new hoses.

Warped bowl covers, although common, would more likely result in drivability issues than excess fuel consumption.


pull(s)/choke not correctly adjusted, or choke not opening...
It seems to be doing its job, but it is late spring in AZ, so who knows if it is in fact working

As long as the choke is opening properly as it warms, no worries.


leaking fuel well plugs or accelerator passage lead plug...
What could cause that? I did blow out all the little nooks and crannys I saw before I reassembled.

This is a chronic issue with QJets and results from their method of construction.  It's correctable by burnishing the secondary fuel well protrusions and sealing them with Devcon or JB Weld.  Same approach is used for the accelerator pump passage plug.


idle mixture screws set too rich...
I thought the same, and turned them back in to snug, then backed out two turns. They went in two and a half before they hit snug.

You are probably close on your mixture adjustment, assuming smooth idle and no black or noxious exhaust fumes.


air bleeds plugged...
Misc debris in there?

If the idle bleeds are plugged with dirt/debris, you might experience idle and transition problems.  Plugged main bleeds can cause early main nozzle tip-in and higher fuel consumption.  Watch the main nozzles at idle and off-idle; there should be no fuel emitting from them.  High float setting can also cause early tip-in.


vacuum hoses improperly routed/connected...
pics attached of the vacuum hoses.
She's running real nice, just drinking gas like its a buck a gallon. lol
The egr is running into the port on the side, the pulloff to the lower, and that upper hose is going to the vacuum advance.

EGR should be connected to ported vacuum, generally through a TVS/PVS.  The pull-off is plumbed correctly.

[slammed79]

wrong float, float level incorrect, or needle valve improperly 'hooked' to float...
I bought the float at the same time I bought the kit, and the clerk at Napa went off my carb number for the parts, so I'd hope I got the right stuff. I did set the float level, but that was the only part I was unsure of when I did the job. The carb # is 17058212. The stupid little clip on the needle valve was hooked on as I found it before.

Issues with the float/needle valve can cause it to run rich.  If the new and old floats appear the same, no worries.  If you're not sure of the float adjustment, however, recheck it!  High float setting can cause early tip-in of the main fuel nozzles and increase fuel consumption.  This is probably the most likely scenario.  Instructions and a gauge should have come with your kit.  The needle shouldn't be hooked into one of the 'holes' on the float, because that can interfere with needle valve function, causing it to hang open.

It isn't hooked into the hole, I made darned sure of that. Unfortunately the gauge and the chart are not with me anymore. I didn't throw them out, I just can't for the life of me figure out where I put them.

Do you happen to know the float level for that carb, or where I might find it on the interwebs?

I'll get the vacuum hoses swapped around after I put the carb on again.

[bd]

Adjustment Parameters for 17058212:

Float Level =  7/16"
Pump Rod Location =  Inner
Choke Fast Idle Cam =  42°
Front Choke Pull-Off =  26-1/2°
Secondary Air Valve Spring Windup =  7/8 Turn
Choke Unloader =  43°
Fast Idle Speed =  1,700 RPM in Park/Neutral

One more thing to verify while the bowl cover is off:  Make sure the accelerator pump discharge check ball is in place under its retaining screw.

[slammed79]

Thanks BD!