To Run with Smog Pump Or to run without ??? Comments Pro/Con

[Guest]

Hi Everyone...(72 Buick Le Sabre Custom 350 4 barrel progressive)I have had people tell me since I don't need smog anymore to run it with the smog pump disconnected.(air injected to manifold). What are my benefits if any? Besides the after rumble in the muffler disappearing does it improve gas? does it make the plugs run hotter? Any help would be great!!!!! [color:\\"blue\\"]

[72Buickguy]

All the pump does is to inject air near the exhaust valves to burn off anything in the exhaust that is still hot enough to burn. Leaving it on uses a little extra horsepower to run the pump, probably makes the exhaust temp hotter and is noisier. Might reduce pollution too. When the pump siezes, it probably will cause the fan belt to fail too.

[Centurion]

geckodude, welcome to the BCA Forum.

It's great to see another owner of an early '70's full-size Buick here on the forum. Please tell us more about your car; we're eager to hear all about it!

[NTX5467]

The whole idea of the A.I.R. pump is to further burn-off hydrocarbons that might have been left unburned in the combustion chamber by adding more air to the exhaust. It might take a few more horsepower to run, but you'd probably not know it in normal driving. I believe that the earlier systems might have been calibrated just a hair richer to make them work better, but don't know that for sure. GM's formal name for the system was "Air Injection Reactor" system. Ford called their similar system "ThermActor".

There was an article in CAR LIFE magazine in the late '60s about the new air injection systems. One comment was that as the injection of air into the exhaust manifolds to "keep the fire going outside of the combustion chamber" could result in the exhaust systems having more back pressure (more hot gas in the same diameter exhaust pipes). The theory sounds credible, but I don't know if anyone ever tested it out.

In any of the air injection systems, there will be check valves that keep the hot exhaust where it needs to be in that system--in the exhaust system. These check valves prevent the heat of the exhaust from getting back toward the switching valve and pump hoses/pipes, plus the air being pumped through them will help keep them cool too. When the valve(s) fail, for whatever reason, the manifold that attaches to the exhaust manifold can deteriorate quickly and leak (even the chrome plated ones end up with just a thin layer of plating holding them together when this happens) and let exhaust heat progressively move into the upstream areas of the system.

As for air pollution issues, I remember seeing a feature car in a hot rod magazine with an air pump. Seems it had a smaller pulley on the pump so that it helped dilute the exhaust output and made it "street legal" in that state.

I would definitely check your state vehicle inspection/emissions statutes to see what they might be and how your vehicle might be affected by them. This would be a key issue of whether you could take it off or not, I suspect.

If you took the belt off and left everything else intact, sooner or later the check valves will fail and cause problems (some of which I mentioned above, which I've seen happen on later model vehicles). In the case of some mid-'80s GM cars I've seen where the valves failed, if left alone, the heat would melt the plastic switching valve and cause a "thermal event" underhood. As most of the earlier systems had rubber hoses in them, similar issues.

If you took the system off, yet the state inspection people claimed the system needed to be there, that's another issue. Usually, if the exhaust manifold has some plugs in it, that's a dead giveaway that something in the system has been altered and just cause for them to get out their "book" to see what might be missing. And then there's the long-standing federal statutes on disabling any emissions control hardware. Even if you could sneak it by with an age or limited use exemption, please make sure you have the vehicle running as good as it can be. Don't forget to plug off any vacuum lines that might have been between the diverter valve and the carburetor/intake manifold if you remove the system.

I suspect the pump could be obtained in the remanufactured version. Diverter valve might be harder to find, just as the air pump distribution manifold for each exhaust manifold, yet you might be able to adapt something from a later model (similar) engine with an air pump on it too.

I doubt seriously that any mechanical engine problems would result from the removal of the system, but I would recommend either "no pump equipment" or "functioning pump equipment"--your judgment call.

Just some thoughts,

NTX5467