A.I.R. / Emissions Question

[Texason67]

A.I.R. / Emissions Question 1974

Hello all,

This is my first post. This is a great forum.

I just recently purchased a 74 vette with L-82. Although it runs and drives, it is by all measures a restoration project. Thus, I'm sure I'll be drawing on the wealth of knowledge found on this site for many months to come. Thank you in advance.

The question I have for today concerns A.I.R. and emissions control. My C3 currently has a smog pump (though it doesn't appear to be connected) and what appears to be aftermarket headers with a rail across the top containing small outlets.

1. What is A.I.R. and it's function?
2. Will I need to rehab the smog pump in order to get it inspected?
3. What (if any) other modifications will need to be made if I shed all this stuff?

I'm not a fan of emissions controls, as they rob horsepower. My preference is to remove all emissions control devices and install an exhaust that will increase HP (or at least let her breath).

Thanks again, and please don't feel you have to be short-winded with your answers. Although I've rebuilt several 60s model vehicles, this is my first vette and my first with so much emissions concerns. It's perplexing to me, no CAT converter, true dual exhaust, and a smog pump?

Thanks again!
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[Vettehead Mikey]

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1. What is A.I.R. and it's function?

The acronym stands for Air Injection Reactor I believe. It pumps fresh air into the exhaust manifold to encourage combustion of unburnt fuel from the engine. The pump has a regulator attached to it to control when to pump air and when to divert it elsewhere, according to vacuum measured at the intake manifold

2. Will I need to rehab the smog pump in order to get it inspected?

Depends on how you accurately want to restore the car and what your local smog regulations require.

3. What (if any) other modifications will need to be made if I shed all this stuff?

None.

I'm not a fan of emissions controls, as they rob horsepower.

That's a very common misconception and is not at all true. The smog pump takes less than 1 HP to drive. Other systems like the EGR and evap canister take 0 HP to run. Your engine is low on HP because of cam profile, compression ratio and cylinder head shortcomings, nothing to do with the smog stuff.

My preference is to remove all emissions control devices and install an exhaust that will increase HP (or at least let her breath).

The stock exhaust system is 99% as good as headers, so there's not much to be gained there!


Hope this helps,


Mike

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[Texason67]

Thanks Mike .... definately things I should consider.

 

[Texason67]

***UPDATE***

It seems that Texas requires the A.I.R. system to be functional in order to pass inspection.

Does anyone know if all 74 models had A.I.R.? I think this particular car came from CA.

 

[craig32]

Tex,
Does your state have 'classic' or 'historical' registration? Here in PA, only about 13 of 67 counties have emissions tests (but unfortunately Lycoming is one of them) but if you have classic or antique registration, it isn't required. I have most of the stuff, but since I didn't take it off, I'm not sure how it goes on anyway. Good luck with the project!

Craig

 

[JohnZ]

***UPDATE***

It seems that Texas requires the A.I.R. system to be functional in order to pass inspection.

Does anyone know if all 74 models had A.I.R.? I think this particular car came from CA.

All 74's had A.I.R. except the Federal L-48 (base engine) automatic, so your L82 had A.I.R; '74 L-82 suffix codes on the front pad stamp were as follows:

CLH = California automatic
CLD = Federal automatic
CLR = Federal 4-speed
CLS = California 4-speed

If it's a real L-82, the 5th digit of the car's VIN will be a "T"; base engine cars (L-48) had a "J" in that position.

The only emission-related external components on your engine that affected performance were the initial timing and centrifugal advance curve, carburetor calibration, EGR, and having the distributor vacuum advance connected to "ported" vacuum instead of full manfold vacuum; the A.I.R. pump and plumbing had virtually no effect whatsoever on performance.

 

[Texason67]

All 74's had A.I.R. except the Federal L-48 (base engine) automatic, so your L82 had A.I.R; '74 L-82 suffix codes on the front pad stamp were as follows:

CLH = California automatic
CLD = Federal automatic
CLR = Federal 4-speed
CLS = California 4-speed

If it's a real L-82, the 5th digit of the car's VIN will be a "T"; base engine cars (L-48) had a "J" in that position.

The only emission-related external components on your engine that affected performance were the initial timing and centrifugal advance curve, carburetor calibration, EGR, and having the distributor vacuum advance connected to "ported" vacuum instead of full manfold vacuum; the A.I.R. pump and plumbing had virtually no effect whatsoever on performance.

Thanks for the information....
The VIN has the "T".

Do you have any recommendations for the other "external components that affect performance?" I'd like to set her up so that she can perform well, but retain "legal" status.

That said, I may just forget "original" and go for the gusto ... it is a 'vette afterall. She needs to scream.

Thanks again, and any advice you can offer will be appreciated.
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[JohnZ]

Thanks for the information....
The VIN has the "T".

Do you have any recommendations for the other "external components that affect performance?" I'd like to set her up so that she can perform well, but retain "legal" status.

That said, I may just forget "original" and go for the gusto ... it is a 'vette afterall. She needs to scream.

Thanks again, and any advice you can offer will be appreciated.

​

You can improve driveability and performance somewhat at very little cost without affecting external appearance by re-curving the centrifugal advance in the distributor (bringing advance in sooner) and by changing the vacuum source to the distributor vacuum advance can from "ported" vacuum (no vacuum advance at idle) to full manifold vacuum (full vacuum advance at idle).

 

[Texason67]

You can improve driveability and performance somewhat at very little cost without affecting external appearance by re-curving the centrifugal advance in the distributor (bringing advance in sooner) and by changing the vacuum source to the distributor vacuum advance can from "ported" vacuum (no vacuum advance at idle) to full manifold vacuum (full vacuum advance at idle).

Thanks for the tip, I'll keep that in mind for sure.
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