Q-Jets got nicknamed "Quadra-bogs" because, as delivered by the factory, they weren't tuned for performance. Tuning usually tended to comply with the EPA anti-smog specs which usually meant lean. If you came onto the them the motor would lay down because it wasn't getting enough fuel. Stock, the AFR was someting like 14/1 meaning 14 parts air to 1 part fuel. Tuners will tell you that the ideal AFR is somewhere around 13.?/1 to a high 12.?/1 The ? is in acknowledgement that the value could be something like 13.3 or similar, not just a whole number.
Because the idle mixture screws were set and then covered/sealed, You could easily tell if a carb had been tweaked because the covers over the screws had been pried off to gain access to them. If you just played with the idle mix, your engine would idle better but to get a decent AFR off idle takes a little more work. See, at idle and during normal or standard acceleration, the idle circuit is actually what is doing the job of feeding fuel into the carb to be mixed with the inbound air and sent to the combustion chambers. This changes as the car speeds up, going from the idle circuit to the main circuit, at which point the subject shifts over to things like the main needles and matching seats, or the jets, depending on whose carb and fuel delivery method is being bench raced.
Holleys are about the easiest to get into and do jet changes; after all they are only about one step removed from a soup can that has had a small hole punched in it for the fuel to drip out.
Quadrajets are more complicated, for values of the term. At this point,if you want to become a Q-jet genius, the library, speciality how to books or on line are your best options arguably.
Many people love them, some for how they perform, others for how they make great paperweights.
Nick
Because the idle mixture screws were set and then covered/sealed, You could easily tell if a carb had been tweaked because the covers over the screws had been pried off to gain access to them. If you just played with the idle mix, your engine would idle better but to get a decent AFR off idle takes a little more work. See, at idle and during normal or standard acceleration, the idle circuit is actually what is doing the job of feeding fuel into the carb to be mixed with the inbound air and sent to the combustion chambers. This changes as the car speeds up, going from the idle circuit to the main circuit, at which point the subject shifts over to things like the main needles and matching seats, or the jets, depending on whose carb and fuel delivery method is being bench raced.
Holleys are about the easiest to get into and do jet changes; after all they are only about one step removed from a soup can that has had a small hole punched in it for the fuel to drip out.
Quadrajets are more complicated, for values of the term. At this point,if you want to become a Q-jet genius, the library, speciality how to books or on line are your best options arguably.
Many people love them, some for how they perform, others for how they make great paperweights.
Nick
