Carter Thermoquads ~ 'More General Information'
that's interesting stuff. I've seen that tiny hole in the feed pipe on baseplate, going to the dashpot hose somewhere before. I may have one of those carbs. the huge jets with the bigger air bleeds combination, that is for emulsion, and emissions reduction. they found that adding emulsion gives a more homogeneous mixture and cleaner burn. it was all done for the sake of meeting emissions standards. we know that a rich mixture gives highest power. maximum power and maximum efficiency and minimum emissions- those are 3 different settings on any carburetor. minimum emissions usually means running on the lean edge, and the least power, or just adequate power. I've been unplugging and blocking EGR valves for 40 years now on my own personal vehicles. every time there's usually a slight gas mileage reduction, but big improvement in part throttle response and drive-ability, because it's richening the mixture at part throttle.
however, more emulsion and, and will, also cause a rich spike at high rpm as well, in certain carb designs. not across the rpm band, just at the very top end. and it creates a real tuning headache. the solution is, reduce the air bleed sizes. Holley 4 barrels are notorious for it. anything beyond .070 idle bleeds, .030" high speed bleeds, in combination begins to cause delayed main metering, lean bottom end, but rich spike at high rpm. the bigger the bleeds get beyond that point, the worse the spike is.
the devices put on cars to meet emissions standards border on downright silly. pushing more exhaust into the intake tract, to dilute and cool the charge. wth ? sure it will pollute less. it will also run less. (laughter..)
we had a 2003 Saturn station wagon that had an electric air pump that ran like a hair dryer, and pumped air into the exhaust manifolds just so the car could meet emissions during cold startups. it was noisy as hell. it also led to repeatedly cracking the exhaust manifolds, because it would cause massive secondary ignition in the exhaust manifold, and overheat it. it cracked 3 times, I replaced it once, and had it welded once- in the life of the car. see they don't mind how they get it, they just need to meet the standard to sell the car. if you can put a big electric motor on the car and pump fresh air from outside into the exhaust stream so it dilutes the exhaust, and the tailpipe emissions go down, presto you met the emissions standards. it's like adding water to beer to get the alcohol content under 3%. but it ends up tasting lousy like watered down beer.
the holes drilled differently on each side of the secondary spray bar nozzles, that was to get even distribution for the oem intake manifolds. there was a guy who actually dyno tested tons of TQ carbs on engines working at Chrysler in the 1970-80's, he posted that it was a real PITA to get those TQ/iron intake combos to have even distribution. If the carb is going on an aftermarket intake manifold, I'd most definitely make both spray bars have even sizes holes.
engineers will add more emulsion, get the engine to run cleaner at idle, off idle, midrange, and not worry about the top end so much. because most of the cars never saw high rpm use in 4 doors, station wagons, pickup trucks, etc. if you remember, TQ's were known for making a lot of noise at WOT, but never really going anywhere from about 1975-onward. hence the name "thermobog". and "quadrabog" for the GM Qjets. they bogged right from the factory. I remember watching Hollywood movies with police chase scenes and you could hear the TQ 4 barrel kicking in and the car could not even turn a tire. basically all the GM, Ford, Mopar cars ran like that from about 1975-onward. a 1979 Trans Am with 400 Pontiac engine and Qjet made a whopping 220HP ?? that was only 20hp more than my old 2003 Monte Carlo 3800 Series II V6 3.8 liter 231cid. by comparison, a 1969-70 Ram Air IV 400 in a GTO or TA made about twice as much HP, and was actually under-rated at 370HP. bone stock examples have dynoed 400HP. It's a sad thing what happened to the American V8 engines. they took the octane and compression away, pushed exhaust into the intake tract with EGR, and choked the exhaust further with a cat converter. then retarded the timing, and pumped fresh air into the exhaust with AIR injection. and leaned the living hell out of the carb to boot, and put very tall gears in the rear axle. they crucified those motors with emissions controls and design compromises, and crappy fuel- for very little real gain in emissions or mileage. it was all a political stunt. it's a wonder they ran at all. looking back now, it was done tongue in cheek. the Feds made them put it all on there. and we took it all back off, and basically drove cars with 2 points less compression and low octane fuel.