Far as I know, the Edelbrock Q-Jet RPM (P/N 1910) was advertised as 850 CFM, but was the identical casting to certain Carter Q-Jets formerly produced for GM except for removing the "Carter" branding, and substituting a bigass "W" for Weber. It was rated at 850 CFM "at the sales brochure", not due to anything special. I have one on my '66 Toronado/455 Olds.
The whole Edelbrock Q-Jet line traces back to Weber buying some or all of the Carter Carburetor tooling; Weber built AFBs, AVS, and Q-Jets off of the Carter tooling under contract to Edelbrock. Cliff Ruggles said the quality went down from the genuine Carter-built carbs, (which were not as good as Rochester-built Q-Jets) the calibration changed over time, and he doesn't especially like any of the Edelbrock offerings--although I think that was prior to Edelbrock building a Holley-style carb with adjustable everything. Other folks on a Pontiac forum I pay attention to have also complained about the Edelbrock AFB and AVS carbs. They're "calibrated for Chevys, so they don't work right on Pontiacs". I guess Carter had a heap of calibration parts--air doors and more--that Weber is not making for Edelbrock.
The aneroid bellows was used for one year--1975--the way I remember it, and only on select models. It compensated for altitude changes. Caused a lot of problems. It was gone the next year.
MOST of the '75--'80-ish "Mod Quad" (Modified Quadrajet) carbs got the plastic filler "shot glass" instead.
When they went to computer control, they re-purposed that part of the casting to accommodate the Mixture Control Solenoid. The MCS was how the computer adjusted the part-throttle fuel mixture based on O2 sensor feedback. The normal metering rods, jets, air bleeds, and channel restrictions got the fueling "close", the MCS only controlled the "fine tuning" on the primary side. And at WFO, the computer wasn't really in control of the carb, I think everything went "full rich" on the primary side, and the secondary side of the Q-Jet never did have computer control.
The final use of that section of the carb casting, was for an electric solenoid in the accelerator pump circuit used on NON-computer-controlled light-duty trucks up to '84--'85, something like that. There was a temperature switch, and a solenoid that looked like a mixture-control solenoid, but a different color. The solenoid would activate based on temperature; increasing or decreasing the accelerator pump shot.
Then there's what the Oldsmobile Guys call the "Patty Melt" Q-Jets. Some of the higher-end cars--the '66 Toronados for example, but they weren't the only ones--got a "pressure balanced" needle and seat assembly. They were completely insensitive to fuel pressure within their working range, making float bowl fuel level easy to control. The problem in this case was the needle and seat assembly relied on a rubber diaphragm as part of the plumbing. When the rubber diaphragm ruptured, the fuel flow was uncontrollable. The carbs would overflow with fuel, and cause engine fires. How this got termed "Patty Melt" is beyond me...talk to the Olds Guys. I suppose that the result of the engine fire was that the poor carburetor melted into a patty of zinc and steel.
In addition, I have a Toronado fuel pump from that era. It has a damping chamber to reduce fuel pulsation pressure spikes. Perhaps this was to make life easier on that pressre-balanced needle 'n' seat arrangement.
The whole Edelbrock Q-Jet line traces back to Weber buying some or all of the Carter Carburetor tooling; Weber built AFBs, AVS, and Q-Jets off of the Carter tooling under contract to Edelbrock. Cliff Ruggles said the quality went down from the genuine Carter-built carbs, (which were not as good as Rochester-built Q-Jets) the calibration changed over time, and he doesn't especially like any of the Edelbrock offerings--although I think that was prior to Edelbrock building a Holley-style carb with adjustable everything. Other folks on a Pontiac forum I pay attention to have also complained about the Edelbrock AFB and AVS carbs. They're "calibrated for Chevys, so they don't work right on Pontiacs". I guess Carter had a heap of calibration parts--air doors and more--that Weber is not making for Edelbrock.
The aneroid bellows, or the shot-glass that replaced it?
The aneroid bellows was used for one year--1975--the way I remember it, and only on select models. It compensated for altitude changes. Caused a lot of problems. It was gone the next year.
MOST of the '75--'80-ish "Mod Quad" (Modified Quadrajet) carbs got the plastic filler "shot glass" instead.
When they went to computer control, they re-purposed that part of the casting to accommodate the Mixture Control Solenoid. The MCS was how the computer adjusted the part-throttle fuel mixture based on O2 sensor feedback. The normal metering rods, jets, air bleeds, and channel restrictions got the fueling "close", the MCS only controlled the "fine tuning" on the primary side. And at WFO, the computer wasn't really in control of the carb, I think everything went "full rich" on the primary side, and the secondary side of the Q-Jet never did have computer control.
The final use of that section of the carb casting, was for an electric solenoid in the accelerator pump circuit used on NON-computer-controlled light-duty trucks up to '84--'85, something like that. There was a temperature switch, and a solenoid that looked like a mixture-control solenoid, but a different color. The solenoid would activate based on temperature; increasing or decreasing the accelerator pump shot.
True. The earliest Q-Jets that had normal needles/seats were the worst for this, later ones had revised geometry on the float arm that provided greater leverage on the needle--worked better.
Then there's what the Oldsmobile Guys call the "Patty Melt" Q-Jets. Some of the higher-end cars--the '66 Toronados for example, but they weren't the only ones--got a "pressure balanced" needle and seat assembly. They were completely insensitive to fuel pressure within their working range, making float bowl fuel level easy to control. The problem in this case was the needle and seat assembly relied on a rubber diaphragm as part of the plumbing. When the rubber diaphragm ruptured, the fuel flow was uncontrollable. The carbs would overflow with fuel, and cause engine fires. How this got termed "Patty Melt" is beyond me...talk to the Olds Guys. I suppose that the result of the engine fire was that the poor carburetor melted into a patty of zinc and steel.
In addition, I have a Toronado fuel pump from that era. It has a damping chamber to reduce fuel pulsation pressure spikes. Perhaps this was to make life easier on that pressre-balanced needle 'n' seat arrangement.
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......or avoiding the cost and chinese-quality of TPS, IAC, MAP / MAF, CPS (crank and camshaft), knock, etc sensors required for proper inputs to the ECU controlling the EFI. Anyone that's purchased a Standard, Delphi or..wait for it..HOLLEY sensor for any EFI application in the last 10 years can relate.
