UPDATE: Many problems solved thanks to this site!

[86BlackBurban]

I want to start off by thanking everyone in the forum for all of the invaluable assistance with this QJet build! I'm so glad I spent the time rebuilding this carb the right way vs going with the Holley that came with the donor engine. Had many problems with the original carb but slowly and surely they were conquered and now this truck runs nearly perfect!!! A few notes on what happened:

Bought a 1986 Chevy Suburban 350 RWD with 71K original miles last September - motor exploded halfway home and eventually found a replacement 350 with a towing cam. Got everything back together and slapped the original QJet carb onto this towing motor. Did not want to run initially, after some jury-rigging, it ran, sorta...

Took off the carb and the first thing I noticed was the side-play in both throttle shafts which led me to this site...Got the a custom rebuild kit along with the book, and set out to get intimate with my carb 

Wasn't really dirty on the inside except the primary side was always wet...suggesting a gasket leak. Airhorn was warped almost 1/16" across the front and couldn't find another straight one in the parts yard, so I hand-sanded it flush which stopped that problem. New jets, metering rods, idle tubes, everything that moved inside the carb was polished with 1000 grit paper with the exception of the throttle plates which were beadblasted and kept rough for fuel atomization. Had very erratic idle until I found that the secondaries weren't closing completely due to a weak return spring  but that's resolved as well. Bronze-bushed both the primary and secondary throttle shafts and now the action is perfect...little to no chance for an air leak in that area now...

Polished the inside of both primary and secondary bores with strips of sandpaper and a Dremel tool, with final sanding done with 1000 grit paper in the direction of airflow. May have increased airflow 1% - or maybe not - but theoretically air should slip past the surfaces a little better. Not really looking for a CFM increase here, but want to basically deburr and "gasket match" all three levels of the carb - hopefully for a little crisper throttle response 

Even with the vehicle only have 71K original miles, this carb was worn out in many areas - and there I sat 6 months ago thinking it was fine...life is certainly an education!

I ended up drilling .125" holes in each primary throttle plate for more idle-bypass air - and this seemed to really help the idle circuit after pulling out my hair adjusting APT and mixture without any real effect.  Currently it runs almost perfect now - good enough to be a daily driver - but the next step is using an AFR gauge along with APT, jets, and mixture screws to enhance it further.

ALso have switched to a 180*F stat - just to keep test conditions close to most other people. Very happy with the way things turned out and it seems there is plenty of potential left! Once again - thank you for all of your experience and will keep yall posted on tuning results!

[omaha]

I think that is great! And, you know what, you now have the knowledge to do this again if need be. Say if someone else is having a problem with their carb. The hard part is convincing folks that the Q-jet is a better carb sometimes, but now you have the proof, just point to your 'burb. Congrats!!

[86BlackBurban]

Done some tinkering here and there, but overall things are still going very well. Instead of .072" jets, I've found that raising the float level 1/16" and using .066" jets and THEN tuning the APT works even better with no loss of power or any major stumbling issues...

It runs a little warmer (leaner) this way, and warms up a whole lot faster when cold...surely the mileage HAS to be better but no testing on that issue yet...

Kinda curious to see how lean it can get before running into major problems...will keep yall posted!!!

[429bbf]

what your going to find out (at least this is my exp.)that it will probably still run ok but the milage will suffer when you get to lean.also had this happen on my diesel the lift pump went out. engine still ran fine ,pulled fair, but the petal has to down futher forcing the govenor (meetering rods ) to open futher causing bad milage.

[Ethan1]

I want to start off by thanking everyone in the forum for all of the invaluable assistance with this QJet build! I'm so glad I spent the time rebuilding this carb the right way vs going with the Holley that came with the donor engine. Had many problems with the original carb but slowly and surely they were conquered and now this truck runs nearly perfect!!! A few notes on what happened:

Bought a 1986 Chevy Suburban 350 RWD with 71K original miles last September - motor exploded halfway home and eventually found a replacement 350 with a towing cam. Got everything back together and slapped the original QJet carb onto this towing motor. Did not want to run initially, after some jury-rigging, it ran, sorta...

Took off the carb and the first thing I noticed was the side-play in both throttle shafts which led me to this site...Got the a custom rebuild kit along with the book, and set out to get intimate with my carb 

Wasn't really dirty on the inside except the primary side was always wet...suggesting a gasket leak. Airhorn was warped almost 1/16" across the front and couldn't find another straight one in the parts yard, so I hand-sanded it flush which stopped that problem. New jets, metering rods, idle tubes, everything that moved inside the carb was polished with 1000 grit paper with the exception of the throttle plates which were beadblasted and kept rough for fuel atomization. Had very erratic idle until I found that the secondaries weren't closing completely due to a weak return spring  but that's resolved as well. Bronze-bushed both the primary and secondary throttle shafts and now the action is perfect...little to no chance for an air leak in that area now...

Polished the inside of both primary and secondary bores with strips of sandpaper and a Dremel tool, with final sanding done with 1000 grit paper in the direction of airflow. May have increased airflow 1% - or maybe not - but theoretically air should slip past the surfaces a little better. Not really looking for a CFM increase here, but want to basically deburr and "gasket match" all three levels of the carb - hopefully for a little crisper throttle response 

Even with the vehicle only have 71K original miles, this carb was worn out in many areas - and there I sat 6 months ago thinking it was fine...life is certainly an education!

I ended up drilling .125" holes in each primary throttle plate for more idle-bypass air - and this seemed to really help the idle circuit after pulling out my hair adjusting APT and mixture without any real effect.  Currently it runs almost perfect now - good enough to be a daily driver - but the next step is using an AFR gauge along with APT, jets, and mixture screws to enhance it further.

ALso have switched to a 180*F stat - just to keep test conditions close to most other people. Very happy with the way things turned out and it seems there is plenty of potential left! Once again - thank you for all of your experience and will keep yall posted on tuning results!

 This is a great site, isn't it?!