There's considerable misunderstanding of what the various emission controls do, how they work, how they affect engine performance, driveability and efficiency, and the wisdom of altering or disconnecting them. Just because it's an "emission control" does not make it "junk" and does not mean your car will work better if you remove or disable it. Just pulling wires and disconnecting vacuum hoses and dismantling emissions equipment willy-nilly is seldom a productive way to improve driveability, fuel economy, or anything else.
So, here's a rundown on the major systems, what they do, and what they don't:
PCV, Positive Crankcase Ventillation. Definitely a good thing. Keeps the inside of the engine much cleaner than the road draft tube system that came before (through 1960 in California, through 1961 in New York, through 1962 in the rest of North America). PCV reduces engine oil consumption and contamination compared to the old road-draft system. An engine that has no crankcase ventillation system because the PCV system has been disabled (for example by installing two breathers instead of a breather and a PCV valve) will get very dirty inside, very quickly, and will stink. Make sure this system is intact and in good repair.
EGR,
Exhaust Gas Recirculation. This is a system that routes a small amount of exhaust into the intake tract to be inducted into the engine along with the fresh fuel/air mixture charge. This is done to reduce peak combustion chamber temperature: even though the exhaust is hot, it is mostly inert (cannot burn) and so the peak heat in the combustion chamber is reduced. This, in turn, lowers the amount of
NOx, a toxic and dangerous constituent of engine exhaust.
The first EGR system, installed on 1972 California models, was a simple orifice (hole) in the floor of the intake manifold allowing exhaust to leak into the intake through the hot spot or crossover already present to heat the intake manifold. This early system seriously degraded driveability, idle smoothness, ease of starting, performance, and economy. For 1973, the system was improved considerably with a valve to allow or block the flow of exhaust into the intake manifold. The valve is operated by engine vacuum, which is appied depending on engine temperature and engine load (determined by manifold vacuum level). Nevertheless, in early applications including most '73-'77 cars, this system can still reduce performance and economy. It can also control pinging, but the early control systems are pretty primitive and not very precise. They can often be tweaked using more recent parts for much better control so they don't take a bite out of performance or economy; the system improved with engineers' experience, and once they could control EGR precisely enough for it to work for them instead of against them, it became a useful tool for reducing the tendency for spark knock while allowing more compression and timing advance for good driveability and economy. You can update to a more advanced type of EGR valve that is a direct bolt-on. Standard #EGV490; RockAuto's usually got them available for low cost, and you can knock that down further with those 5% RockAuto discount codes that are always floating around. This valve has a backpressure transducer that modulates vacuum to the EGR valve to match EGR flow rate better to the engine load. Takes a smaller bite out of driveability than the non-transducer type valve.
Some cars originally equipped with EGR will tend to ping if the EGR is disconnected; in most cases this can be addressed by reducing the initial spark advance. If you can't clear up the ping without setting the basic timing at or after TDC (ATDC), though, it's best to rework the distributor's advance curves so as to allow a base timing setting of between 2½° and 8° before TDC (BTDC).
ECS, Evaporation Control System. This consists of your fuel tank, fuel tank cap, carburetor bowl vent and charcoal cannister (on '72-up models. '70-'71 models with ECS used the engine crankcase as a storage place for fuel vapors). This system is completely beneficial — it lets you keep and burn costly gasoline that would otherwise float off into the atmosphere. It takes away absolutely nothing from engine efficiency. It improves safety by making the fuel system a "closed" system. There is no good reason to disconnect or tamper with this system, and doing so in a thoughtless or improper manner creates real safety problems. This system, too, ought to be kept intact and in good repair. Here again, though, the early ('70-'71) system can best be described as "a start"; things got better in '72. See
here for detailed info on both systems and discussion of upgrades.
OSAC, Orifice Spark Advance Control. Now
here is one that takes a giant bite out of driveability, performance, and fuel economy. This system was designed to squeak the cars cheaply past the Federal emissions type approval test so they could be offered for sale. It delays vacuum to the distributor vacuum advance by 7 to 17 seconds, which means lower NOx emissions but also hesitation, mushy acceleration, and poor fuel economy. This is a very easy device to bypass. There's a hose that runs from the carburetor to the OSAC valve (on the passenger side of the firewall in '73, on the air cleaner body starting in '74), and from the OSAC valve to the distributor. To find it, follow the vacuum hose from the distributor to the OSAC valve. To bypass it, simply connect a vacuum line between the carburetor and the distributor, leaving the OSAC valve out of it. You will find an immediate improvement in driveability and mileage.
Air pump ("smog pump"), properly called
secondary air injection. This pump takes almost zero power to spin, does not reduce driveability or economy, and substantially cleans up the exhaust. Usually best to leave it alone, though
the early systems (there's that phrase again!) pumped air full-time into the exhaust ports in the cylinder head whenever the engine was running. This makes the exhaust valves and the whole head run hotter, so that's something to bear in mind when deciding whether to keep it. However, if your car is a '75 or newer model with a catalytic converter,
don't remove or disable the air injection system. If you do, the catalyst will overheat, melt down, and block off your exhaust flow (and perhaps start a nice fire).
TAC, Thermostatic Air Cleaner. This is the air cleaner that has a flexible stovepipe duct running down to a sheetmetal shroud surrounding a portion of the exhaust manifold. This system, too is 100% beneficial. Leave this in place and make sure it's properly working! It improves cold and hot driveability, performance and fuel economy compared to a plain old-fashioned air cleaner assembly.
Catalytic converter: Unlike General Motors' highly restrictive pellet-type converters of the 1970s and early '80s, Chrysler used reasonably good-flowing monolithic ones right from the start, and the ones available in the aftermarket today are even better in terms of flow and efficiency. Catalytic converters aren't a very good mix with carburetors, especially in pre-1981 applications that don't use an oxygen sensor and computer-controlled carburetor to try and maintain a stoichiometric fuel/air ratio, which is the only mix that creates exhaust a catalytic converter can efficiently clean up without heating up to the meltdown point. Still, the exhaust from a catalytic-equipped car is
far less toxic even without feedback mixture control.
Picking a replacement converter is fairly easy. You need one with heavy catalyst loading (to clean up the extra-dirty, poorly-controlled exhaust) and robust substrate (to handle the extra-high heat that comes from operating with poorly-controlled exhaust). It's difficult to find a 2-way (HC/CO) converter any more; you tend to find only the 3-way items (HC/CO/NOx) that have been standard equipment since 1981. The NOx reduction doesn't work very efficiently at all with non-stoichiometric exhaust, but it can work somewhat to add extra oxygen (one of the products of the reduction reaction) which then helps a little with the HC/CO oxidation reaction. Some Chrysler vehicles have small converters located in the headpipe right off the exhaust manifold in addition to the larger under-floor converter; if your local regulations allow (or are silent on the particular matter), you can install regular headpipes and a modern efficient 3-way catalyst under the floor. .
So: a converter meant for a heavy-duty truck with a large engine in California. See
here for more detailed info.
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I guess I'll wait as long as I need until I feel comfortable knowing what to take out from what you've said, but I'd like to get at it tomorrow... -typing my mind here
