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lt1silverhawk 07-28-2012 12:44 PM

General Engine Question: A.I.R. Pumps - How do they work?
Hi All,

I just had a few general questions regarding A.I.R. pumps that I wasn't able to find the answers to online.

How exactly does a A.I.R. pump operate internally? I am working on my '77 Chevy truck (non-EGR) and have a few things removed. I see the A.I.R. pump operates off the v-belt, so it obviously operates based on engine speed.

Also, how can one tell if the A.I.R. pump has gone bad? Do they eventually go bad?

Thanks in advance! :thumbup:

Mr. P-Body 07-28-2012 01:55 PM

Air Injection Reactor.... That's the air pump pushing "fresh" (cooler) air into the exhaust system at the valve, "continuing" the burn as the spent mixture goes through the exhaust system. This significantly reduces emmissions. There's a slight parasitic loss from the pump, but performance "loss" is grossly exagerated by "lore". In fact, one can use the pump to their advantage. Small block Chevy in particular, uses tubes that are long and inject the air right near the valve itself. When installing headers in California "back in the day", we had to adhere to rules regarding disabling any emmission control. Can't do it. So we bent the tubes in a "curl", so they'd go down the header tube instead of into the port. The result was a slight gain in scavenging by creating a lower pressure in the pipe than the chamber/port. And all still passing "smog".

Usually, a failed pump is locked up. Sometimes they'll squeal prior. A blubbering sound can also indicate a problem.



boothboy 07-28-2012 03:03 PM

Just a side note to "back in the day" I was working at a Ford dealership in1966 the year Ford started using A.I.R. pumps. Ford called them Thermactor pumps. We'ed get a new car in or one on warranty with a squeaking pump. The factory fix was to pour about half of a quart of transmission fluid down the pump inlet while the engine was running.The second time we did this we wisely put the car out at the back fence. Instant thick white smoke. Not a live mosquito within a five mile radius. Talk about air quality!

LATECH 07-28-2012 03:59 PM

Many newer Fuel injected cars have an AIR pump. It runs for a minute or so when the engine is first started cold. Its purpose is to clean the unburnt hydrocarbons quickly, as when a cold engine is started the mixture is enriched. It also serves to heat the catalytic converter up very quickly, so it can function ASAP. Pretty smart.
Those are electric pumps, like a small leafblower,not belt driven.

lt1silverhawk 07-30-2012 11:51 AM

Thank you everyone for the informative and helpful responses! :thumbup:

@Jim: The info on gaining performance is very interesting. I hear you the emissions in Califoania. I was looking for some street legal headers with the A.I.R. tubes and a C.A.R.B. certification for my truck. It seems like only two companies make them and charge a pretty penny.

@Boothboy: So that's why the smog requirements are so strict in California! Lol!

@LATECH: That is pretty clever. I've never seen it on any of the newer cars I've owned or driven.

Mr. P-Body 07-30-2012 11:58 AM

In those days, Hooker was the ONLY one to bother with. I would imagine they still make them. If Hooker makes something, it's going to be "the best" for an "out of the box" header (IMO).


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