Q-Jet + low vac = rich at idle??
09-21-2003, 09:17 PM
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Q-Jet + low vac = rich at idle??
My 72 runs great, except that it seems to run rich (smells strong, burns eyes)at idle. Does my low (13") of vacuum at idle (600 rpm) cause the Q-Jet to run rich? I seem to recall that this could happen. If so....the fix?? Thanks!
09-21-2003, 11:02 PM
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Re: Q-Jet + low vac = rich at idle?? (72Shark)
When I had a Q-jet on my 69 I noticed the same thing. At idle the fumes were so strong that my eyes would water. I never was able to get the thing to lean out at idle. I went to a Holley and the problem went away. I'm sure that problem was caused from running a cheap parts store rebuilt Q-jet.
One that is properly setup from Lars would probably idle without all the fumes.
One that is properly setup from Lars would probably idle without all the fumes.
09-21-2003, 11:06 PM
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Re: Q-Jet + low vac = rich at idle?? (72Shark)
I just read your second post, and that's wierd, normally when then choke is closed the car is running at its richest.
09-22-2003, 04:12 AM
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Re: Q-Jet + low vac = rich at idle?? (Smokehouse69)
adjust the mixture using a vacuum gage.
Set you base idle around 800 - 600 is a bit low in my book.
Shut off the engine then connect a vacuum gage.
Turn both mixture screws in all the way and then turn the both back out 2 full turns each.
Start car.
Turn each mixture screw out 1 turn at a time. When you have added 1 turn to each, blip the throttle a couple times to clear it.
Keep turning mixture screws out equally and clearing the throttle until you have reached you highest vacuum reading. Make sure to keep adjusting the idle to keep 800 RPM.
If you are tuning for emissions, once you have found your best vacuum reading, turn each screw back in 1/2 turn to lean it out.
This should get you the best settings. I have done it with my Vette and my truck.
My truck just passed emissions with idle readings of 0.00 Carbon Monoxide (max allowed in AZ is 2.00) and 7 PPM Hydrocarbons (max allowed is 250).
By the way, loaded readings on this carb were 0.00 Carbon (1.50 max allowed) and 23 hydrocarbons (250 max allowed).
My Vette has also passed 2 years in a row with equally impressive numbers.
Set you base idle around 800 - 600 is a bit low in my book.
Shut off the engine then connect a vacuum gage.
Turn both mixture screws in all the way and then turn the both back out 2 full turns each.
Start car.
Turn each mixture screw out 1 turn at a time. When you have added 1 turn to each, blip the throttle a couple times to clear it.
Keep turning mixture screws out equally and clearing the throttle until you have reached you highest vacuum reading. Make sure to keep adjusting the idle to keep 800 RPM.
If you are tuning for emissions, once you have found your best vacuum reading, turn each screw back in 1/2 turn to lean it out.
This should get you the best settings. I have done it with my Vette and my truck.
My truck just passed emissions with idle readings of 0.00 Carbon Monoxide (max allowed in AZ is 2.00) and 7 PPM Hydrocarbons (max allowed is 250).
By the way, loaded readings on this carb were 0.00 Carbon (1.50 max allowed) and 23 hydrocarbons (250 max allowed).
My Vette has also passed 2 years in a row with equally impressive numbers.
