Another quadrajet problem
#23
I also think rebuild went wrong get vacuum diagram make sure all lines are connected in proper place some ports are timed. I also agree about sounds, like vac leak...but float improper set or float needle in wrong location on hanger bar causing flooding. it can be tricky to set float in place with needle a dangling.
#24
Found out from the guy that rebuilt it that one of the rods was bent...... he straightened it out but like i said it was running fine before and now improving it has proven to be the downfall. i'm torn now between the rebuild being the cause and the fact that putting on the air cleaner changes the rpm. vacuum vs. rebuild. don't want to invest money in a differant carb if it's just a simple fix.
#25
Race Director
Found out from the guy that rebuilt it that one of the rods was bent...... he straightened it out but like i said it was running fine before and now improving it has proven to be the downfall. i'm torn now between the rebuild being the cause and the fact that putting on the air cleaner changes the rpm. vacuum vs. rebuild. don't want to invest money in a differant carb if it's just a simple fix.
You can do this yourself, but if it's your first carb project it won't be easy.
#26
sick of the headaches...... anyone ever used www.guaranteedcarburetors.com ? can get a rebuilt with warranty for $188 after core return. seems like it would be worth it just to save time.
#28
Instructor
Qjets are seen to be so complicated, but they are not. Just need to understand them a little
1) idle circuit- the idle is merely a tube and an adjustment screw, if the tube is clean and the screw is anywhere near the right place (3 or four turns from the seat) then it will idle. If not look for a timing, ignition, or vacuum issue
2) off idle - if it bogs down off idle, check the accelerator pump
3) partial throttle - this is the primary. If the jets and rods are stock ( see Lars paper) it should work fairly well. If it stumbles or if gas is dripping into the carb, check the float height. If it is lean or rich, somebody probably changed the jets and rods,bring them back to stock. Might need tuning for a modified engine, read Lars paper.
4) near wot or wot-- the secondaries open. They are mechanical, very little can stop them, except the choke lockout. You can see the lockout at the bottom of the passenger side. After the engine is warm, the lockout should be removed. then the air valves on the top of the carb open with vacuum. If you can push them open with your fingers,they are probably ok
5) choke- when cold, full throttle locks in the high idle and the locks out the secondary, the choke valve closes on top of the primary. After the engine warms, a blip on the throttle releases the high idle and the lockout. If you do not see the choke valve slowly opening during warmup then the choke is defective. If the lockouts and high idle do not set or clear, a mechanical issue with the linkage ( or someone tried to modify it)
I realize this is simple, but it sets the groundwork. If everything looks like this, it is probably not the most blamed part of the engine for performance issues, look for ignition issues
1) idle circuit- the idle is merely a tube and an adjustment screw, if the tube is clean and the screw is anywhere near the right place (3 or four turns from the seat) then it will idle. If not look for a timing, ignition, or vacuum issue
2) off idle - if it bogs down off idle, check the accelerator pump
3) partial throttle - this is the primary. If the jets and rods are stock ( see Lars paper) it should work fairly well. If it stumbles or if gas is dripping into the carb, check the float height. If it is lean or rich, somebody probably changed the jets and rods,bring them back to stock. Might need tuning for a modified engine, read Lars paper.
4) near wot or wot-- the secondaries open. They are mechanical, very little can stop them, except the choke lockout. You can see the lockout at the bottom of the passenger side. After the engine is warm, the lockout should be removed. then the air valves on the top of the carb open with vacuum. If you can push them open with your fingers,they are probably ok
5) choke- when cold, full throttle locks in the high idle and the locks out the secondary, the choke valve closes on top of the primary. After the engine warms, a blip on the throttle releases the high idle and the lockout. If you do not see the choke valve slowly opening during warmup then the choke is defective. If the lockouts and high idle do not set or clear, a mechanical issue with the linkage ( or someone tried to modify it)
I realize this is simple, but it sets the groundwork. If everything looks like this, it is probably not the most blamed part of the engine for performance issues, look for ignition issues
Last edited by wajulia; 07-25-2012 at 07:25 PM.
#29
Instructor
Also need to look at the 81 part of all this. If there is an 80 carb on top an 81 engine, what distributor do you have. If it does not have a vacuum advance (81's do not have vacuum advanced distibuters,they will have a four pin connector on the driver side, it would have had to been changed to a pre 81) that is a big part of your issue.
An 81 without an 81 carb will go into open loop and leave the distributor at 6deg of timing fore ever. It will definitely not run right. Mostly sluggish as hell
Good luck
An 81 without an 81 carb will go into open loop and leave the distributor at 6deg of timing fore ever. It will definitely not run right. Mostly sluggish as hell
Good luck
Last edited by wajulia; 07-25-2012 at 07:29 PM.