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 7/10/05 9:27am
Former Member

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Joined: 10/19/2003
Posts: 33

Hi there,

I've been toying with the idea of removing the smog pump and forced air system on my 1981 Corvette, 5.7 liter. It runs great now, can anyone tell me what else must be done to once removed? I've told you need to rejet the carburator and HEI ingition work?



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 7/10/05 1:15pm
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Frederick, MD - USA

1969 convertible L71 427/435 4-speed black interior

Joined: 9/8/2003
Posts: 3398

The smog pump was already removed from my '78 when I bought the car, but I still have the forced air system. I did have my Q-Jet rebuilt and it did need re-jetting, but I think that was needed more from the somewhat bigger cam than original the previous owner installed.

I removed the original intake manifold and replaced it with an Edelbrock Perfomer without EGR, and also removed the rest of the emissions parts and the car runs much better.

Since my car had the smog pump removed already, I have no way to compare it's performance before and after, but it does run much better after the other modifications I made.
 7/10/05 2:03pm
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Joined: 10/21/2003
Posts: 1220

When I first got my black 79 waaaay back I pulled all the smog stuff . Don't know how much it may have helped performance cause I also put headers and dual exhaust on at the time. When I got the white 79 back in May it had the belt removed from the smog pump. Ran great. Ended up putting the smog pump from the black 79 on it because of a squeeky bearing. Trying to keep it original. Seems to run the same as it did on the 1000 mile trip home when I bought it. But the 81 is computer controlled, soooo...........I sure ain't much help. But it DOES LOOK good without all that junk!  Mike
 7/15/05 10:22pm
kstyerLifetime Member
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1975 C3 Red, T-Tops, Black Interior. All I need is time and money! Getting there!

Joined: 12/2/2003
Posts: 6415

The smog pump blows air up stream to the exhaust manifolds when the engine is cold.  This adds oxygen to the hot exhaust, which has a lot of unburned fuel left due to cold operation.  The hot fuel and oxygen meet, then burn, cleaning up the leftover fuel before it comes out of the tail pipes.  This also creates an 'afterburner' effect and heats the exhaust manifolds.  This helps the engine to warm up faster, but not much.  A few choke adjustment can be made to allow for the warm up time.

If the air is supplied upstream on a warm engine it can cause vapor lock, pinging, and overheating.

When the engine is warm, the air blows downstream to the cat converter.  This supplies oxygen to the cat so it can do it's job better and more completely.

Without the smog pump or A.I.R. ( Air Injector Reactor ) pump, there is a increase in emissions.

Now what other than a slightly extended warm up does this do for driveability?   NOTHING.  It will not affect the way the car runs at all. Removing it will make no difference in performance, fuel mileage, or anything else.  The EPA does not care for it, but Oh Well Too Bad.  Over 25 years it does not matter to the Feds.  Removing the pump is a no harm, no foul operation.   If you like the look, go for it.

The only caution is you MUST seal the holes or tubes that the air pumped through.  Otherwise air will get into the exhaust when it's not wanted, and the oxygen sensor on 81 and 82 C3s will pick up the O2 content, and drive the system rich trying to correct for the O2.  Nothing else has to be done.

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