As far as I understand it, A.I.R. smog system simply pump air into the exhaust. So the performance penalty is only the couple of hp to drive the pump. So why do so many people remove them?

I have a 69 Tri Power and would like to put the A.I.R. system back in for originality and less emissions. Any comments on why I should or should not?

Regards,
Wayne

 

I took my equipment off because it makes it easier to work on the engine, less things to remove. I'm always fiddling with stuff so it saves me time.

 

First off the smog equipment used in the 60's was VERY primitive as well as into the early 80's. The contribution that a SMOG pump does to reduce emissions is VERY small in the overall scheme. The biggest reducer of emissions BY FAR is a cat which your car does not have. In addition to robbing HP and cluttering the engine compartment, the AIR pump exhaust ports extend VERY far into the exhaust manifold-at least 3-4 inches and create turbulence and an obstruction to the exhaust flow-I know since I saw how much when I removed the pump and accessories years ago. Unless you are interested in originality, I would definitely leave the AIR pump off. It really does VERY litttle.

 

I got an email from a friend who stops by the C3 section from time to time but spends most of his time with the C2s. He's seen my previous posts where I had mentioned that the AIR system consumes 1 HP to drive the pump. He thought I'd like to know that it was actually 0.3HP.

Sorry for the confusion.

 

OK I understand less clutter and no appreciable NOS reduction without smog system.

How about that awful unburnt fuel smell at idle. Will smog pump reduce that? As I get older, changing shirt each time after I start the car becomes less appealing.

 

Ha ha ha I think I can spare 0.3hp.

 

The car shouldn't stink that badly even without a smog pump. Has someone been under the hood and modified things?

 

Or the carburetor is out of tune, but I agree it should not be that bad.

 

Well I guess the stink is relative to what we compare it to.

It smells peachy compared to my crate LS7 from 30 years ago. Comparable to the LS5 with Crane Fireball cam I had after the LS7.

Just got this L71. It currently has Brodix aluminum heads and a Straub cam. Saw the cam card somewhere the specs seemed quite reasonable at first glance.

Maybe I'm just spoiled by all the modern day 100hp plus per liter machines that I forget these fabulous Vettes are low tech after all.

 

AFR meter shows about 14.5 at idle.

 

Rookie observation.......I removed the smog pump and all the hoses/valves/etc to be able to work on the 350 SBC on my '34 streetrod truck and I tuned the engine. The exhaust smell became worse so that my eyes watered if I stood behind the vehicle.

Now........I DESPIZE cats...mostly metal cats......but......

That stench caused me to do some research on the internet which caused me to buy two (dual exhausts) "modern mini"-cats designed for a 3-liter engine. I also added an oxygen sensor to one exhaust and used a multimeter to read the sensor in order to adjust the carb on one side and set the other side to match. The exhaust smell and eye-burn went away/there is very little/if any loss of performance, and my grand-kids might have a few more breaths of clean air in 20 years (me too....maybe...LOL).

Since the '68 project car has been previously molested from one end to the other, I will try to "convert it" back to a '68 in looks as much as possible. "Two "mini" cats could be in it's future depending on the space required without the cats "melting" any areas of the firewall or my shoe soles (I realize "under the floorboard" is OUT of the question as far as cabin heat is concerned).

Like Mike Ward said--It shouldn't smell that bad.....but my exhaust did for some unknown-rookie-reason....

Any derogatory remarks would be greatly appreciated LOL.

 

Thanks for the tip. Hmmm... never occurred to me to add cats. I have quite a few used ones lying around from certain Italian race cars from Maranello. Space is going to be a problem though.

 

Pulled mine off the '69 about 6 weeks after I bought the car (used). The sudden noise from the pump sounded like a rod knock (scaring the crap outta me as I was still paying off the loan), and after debugging the noise I decided I didn't want to spend good money on something that effectively just adds visual discomfort and weight to my car.

 

The A.I.R. system relied on low performance engine timing (4 degrees BTDC initial on an L-71) and resultant incomplete combustion in the cylinder to effect the re-burn of combustion products in the exhaust system, thereby lowering the overall emissions at the expense of performance. By running the timing at a more performance oriented 12-16 degrees like is recommended today, you won't be doing much re-burning in the exhaust and the air pump wouldn't be serving much of a purpose. At the higher initial timing, the engine is going to run more efficiently and definitely feel more powerful.

 

they should have used a bigger unit and pumped it into the carburetor.

 

Cause it's ugly.

JIM

 

Super 6's description is exactly correct! A properly/optimally tuned C3 from the late 60's to mid 70's does not need any of the so called emissions crap/equipment used then since it was largely ineffective. A super rich engine run condition (burning eyes) is really not a cat issue. Some may know this already (and I can personally attest to its validity) that even SOME cars-Not all- (and C3's) from the 1975 on until the mid 80's that had cats from the factory could have the cats removed and properly tuned, past the emissions test based on the sniffer test alone (not visual obviously) since the limits back then were MUCH higher than today. Prior to the early 90's, much of the so called emissions control was largely ineffective compared to today which is why so many remove all the emissions equipment on 25+ year old cars driven 500-1,000 miles per year-It's ridiculous!

PS-My 1994 Mustang GT convertible has a magnaflow X pipe with 4 cats-Yes 4- and a maganflow catback system with BBK shorty headers and I would not think of removing the emissions gear on this car. You know why? It works as designed and is very effective with little effect on performance. C3's are a totally different story. Just to be fair!

 

I removed all smog equipment because my vette is modded, not original, I don't go through state inspection, smog stuff is ugly, adds weight, robs power, not compatible with sidepipes, and costs more money for the additional parts.

 

The only real reason to keep an AIR pump and all that ugly ineffective hardware is to pass a visual inspection (if you have to) and/or you have a completely stock engine and want to maintain originality which I can understand as well. From an emissions reduction/performance point of view, this equipment is a big negative!

 

I don't have an air pump on my '72. A Min of Environment officer pulled me over and did a spot check and he pulled the hoses off the vac cannister. Didn't have that raw gas smell before this but the drive home was awful. Put the hoses back on the next day and no more raw gas stench.