1972 emissions pump

[JohnD1956]

Granny's 70 Skylark and I were looking at a 72 Estate Wagon the other day and it had an emissions pump on the engine. Due to inaccessibility of the car I could not get a clear look at what this was hooked to. Would anyone have some experience with this and know if it can be eliminated without any problems ?

I'm not talking about eliminating it from the State's point of view, I mean what is it hooked up to and how much work is it to get it off the motor?

[Smartin]

It should just be a couple bolts and a couple hoses...and a belt. Nothing major. Similar to how the alternator is set up.

[NTX5467]

There's more to that system than just the "pump" itself (which is a significant part of the complete system).

First, there's the pump which pumps air into the exhaust manifold to help "afterburn" the exhaust gases as they exit each cylinder. Then there's the "diverter valve" (on the back of the pump in your picture) which directs the output from the pump to either outside air or into the plumbing which goes to each exhaust manifold.

From the diverter valve, the pump's output flows through (generally) rubber hoses to the "check valves"--which are highly important in the total system. The check valves typically screw onto the distribution manifold for each exhaust manifold. These are "one way" valves which make sure that pump air flows through them and exhaust gases do NOT flow toward the rubber hoses, letting "heat" be where "heat" does not need to be.

The distribution manifolds might appear to just screw into holes in the exhaust manifold, but there are generally little "nozzles" which have a flared end (where the distribution manifold screws "against" them in the manifold and a somewhat crimped end where they stick into the exhaust gas stream.

By observation, when the check valves malfunction, exhaust heat will first overheat the distribution manifolds and make them so thin they eventually fail. On the ones from the middle 1980s, which appeared to be thin-chromed, that thin layer of chrome would be all that was left.

When the diverter valve was later replaced by a computer-controlled "Air Management Valve", generally a "composite" and glued-together mechanism, they melted and sometimes "flamed". Again, a failed check valve let heat be where heat didn't need to be.

Depending upon what titling regulations are in your state and/or municipality, it can be easily determined that your vehicle could have or should have the Air Injection Reactor (A.I.R. system) on it from the factory. Most of those systems were "add-on" systems, basically, so they are not totally dependent upon other engine systems for their mounting and operation.

In reality, the AIR systems were not the great horsepower robbers that many perceived they were. The real issue was that exhaust systems were generally not enlarged to handle the greater volume of hot exhaust gasses (additional heat kept the gasses "expanded" rather than letting them cool as they made their way to the end of the exhaust pipe--at least, that's my theory). One car magazine featured an early Camaro with a 500+ cid Big Block Chevy, which met the basic emissions requirements for that car as it had a highly over-driven AIR pump which diluted the exhaust gases enough to pass for a normal 1967 vehicle--that's what the article said and the basic theory might have a little credibility.

Yes, there's some extra noise, some more clutter in the engine compartment, but that extra 5 or so horsepower it takes to operate that system is not significant in a 200 horsepower "torque" motor. And it's socially and environmentally responsible AND period-correct for the vehicle. Trees are beautiful, but many are too big to hug--just watch out for the ants.

If you need a new air pump, they should be available from the reman parts sources, I suspect. The check valves are pretty generic for well up into the 1990s on many vehicles.

I know that it was somewhat popular in the pre-emissions testing days (visual or chassis dyno) to remove the AIR pumps for many reasons. It was usually obvious what had been done due to the brass pipe plugs that were screwed into the exhaust manifolds. In the past, GM has sold some cast iron plugs (with a "cup" in them that would coincide with a particular size rathet size rather than a hex of pipe plug square top) . . . as all replacement exhaust manifolds came with all of the possible holes already drilled and tapped in them.

Just some thoughts,

NTX5467

[JohnD1956]

Thanks Adam and Willis. I don't know if the car would be available yet, but your answers give good information. I think the driving factor would be the condition of the air manifolds, as I suspect these are no longer available.

I remember a wagon like this passing me one time and it stood out in my mind because I thought; that car sounds like it's making a lot of noise from the exhaust, but it's not going that fast. Chances are it was such an AIR equiped car leading to excessive noise?

I was just surprised to see this pump on the car considering it is not a west coast car.

JD

[NTX5467]

JohnD, even if was not found on the west coast, it could have been spec'd with CA emissions when it was ordered (possibly to get a particular engine combination in a particular body, or similar). In some cases, larger engines were available in CA-spec vehicles than were available with Federal-spec emissions systems, but I don't know that this would be the case with this vehicle.

Initially, the A.I.R. pumps were on manual transmission GM vehicles with automatics being a little easier to get past the emissions tests as the engines were always connected to the transmission and more "under load" during shifts, which manual transmission vehicles were not. But as emissions standards tightened, A.I.R, systems' use was expanded to almost everything and became an integral part of many vehicles' emission compliance.

In those earlier years of emissions controls, Chrysler used an "engine modification" system of leaning out the carb mixtures, raising the idle speeds, and altering the distributor's advance curves. It worked pretty well at little additional cost (from what I understand, their combustion chambers' shapes -- wedge motors -- were a key reason they worked well for Chrysler). When GM and Ford were trying to take the same approach (at the desires of corporate accountants and management, as I understand it), they ran out of time and had to use the A.I.R. and ThermActor (Ford's name) systems for a couple of years until the other systems were ready for production. This was in the middle-later 1960s when CA emissions regulations were first taking hold.

I know of several cases where the CA-spec vehicles had larger engines than the Fed-spec vehicles of the same model. One was the Chevy Monza that got a 262 V-8 in Federal trim but a 350 in CA. Another was in the middle 1980s when a K-10 pickup had only 305s in them but a 350 could be had with CA emissions. And then there were the few years when all Camaros/Firebirds sold in CA had to have the Buick 3800 V-6 in them as the Chevy V-6 (in Federal versions) would not pass CA emissions--surprising performance with less emissions! Chrysler also had a few CA or High Altitude emissions-spec vehicles that also had 4bbls and/or more displacement than the normal Fed-spec vehicles of the same model. As things seem to have evolved now, the main difference in CA and Federal specs is the catalytic converter and possibly a computer chip difference, with the engine specs being pretty much the same for all versions.

Generally, the systems on light duty pickup chassis vehicles differed from what was on the similar cars, due in part for the different size engines. By the middle 1980s, GM C/K light trucks had some emissions systems that had DUAL air pumps and a separate air filter for the pumps rather than using air cleaner or ambient air to feed them. For about six months, GM did not have 454 engines certified for those trucks due to extreme underhood heat situations, but they eventually got things certified. Many of these same engines also had "factory headers" (i.e., stainless steel tubular exhaust manifolds, with 1/4" thick mounting flanges). When fuel injection and tuned intake manifolds came online a few years later, much of the earlier hardware was revised and possibly replaced with new technologies and related equipment.

Possibly one reason the A.I.R. equipped vehicles might have gotten poorer fuel economy than the prior versions was that I believe the carb calibrations were richened-up just a tad. This was done to help support the "after burn" in the exhaust manifolds. In reality, one jet size (for example) would not significantly impact fuel economy, but the lower compression ratios and larger CID displacements would have been more contributing factors than either the mixture or presence of the A.I.R. pump. LOTS of balancing acts were going on in those earlier days of automotive engine emissions controls!

In many cases, the A.I.R. distribution manifolds for many engines are now available from several aftermarket vendors (like the "HELP!" rack people, which is a division of FederalMogul). Same with exhaust manifolds and other prior-dealer-only parts too. By observation, these things have started happening in the past 5 years or so, maybe even a little sooner.

Enjoy!

NTX5467

[55PackardGuy]

As I understood A.I.R. systems, you basically shoot a little fresh air into the hot exhaust gases and get the unburned hydrocarbons burning inside the pipes. Always seemed a little mickey-mouse, but the corporations did what they had to do to cobble together systems that helped lower tailpipe emissions.

All I know is that, with a manual transmission and some aggressive shifting, you could get a heckuva nice rumble and bang through the exhaust when letting off the gas between shifts! Had a 302 in an '84 Mercury Capri that did that... rumbled like a big-block with overrich carb jets. But it was one of the last--if not THE last--"non-computer" 4-barrel (Holley) equipped V8s to pass emissions. And it got outstanding gas mileage: high twenties and even 30 on trips in those 55 mph days, just a touch above idle RPMs at speed in 5th gear. Rumble rumble rumble. Really miss having a car that sounds like that.