FactoryC3
Well-known member
I noted this just after getting my '81 and cannot figure it out. Is it a flame supressor?? Or what? :confused
View attachment 20447
View attachment 20447
Help! What is this sitting inside my air cleaner housing???
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Hib Halverson
Technical Writer for Internet & Print Media
It's a di-inverse flowing confabulator valve?
Ah...no.
Not sure what the heck it is, actually. I'm thinking it's some kind of flow straightener but that's nothing more than a WAG.
Merry Christmas
Ah...no.
Not sure what the heck it is, actually. I'm thinking it's some kind of flow straightener but that's nothing more than a WAG.
Merry Christmas
kpic
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FactoryC3
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Thanks much...
How do you clean it...if you do?
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bill81vette
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I have never seen one of those....
LLC5
Well-known member
Thanks much...
How do you clean it...if you do?
If it is metal screening you could use a solvent, brake cleaner, or carb cleaner. If it is fabric mild soap and water. If it is paper then all you can do is blow air through it, but it will still be restrictive as you will not clean it thoroughly, paper is meant to be thrown away when dirty.
Here is a better idea though - remove it and install a quality air filter. If it were me I would follow the sticker on your air cleaner assembly. Good luck with it.
kpic
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FWIR, the inner one is filled with charcoal.
Most owners pitch them for a K&N; however, I would not throw it away as most 81s are missing it.
Most owners pitch them for a K&N; however, I would not throw it away as most 81s are missing it.
LLC5
Well-known member
Are you saying that the inner filter, that is attached with blue sealant in the picture, is factory installed?
Vettehead Mikey
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Thanks much...
How do you clean it...if you do?
If it's inside the main filter why would it be dirty?
LLC5
Well-known member
Depending on it's composition, fuel vapors and blow by especially if it has charcoal in it, if it is just a screen then it is probably not plugged and is serviceable. If it is a charcoal composition then it is not serviceable, and it may be a form of evaporative emissions filter (possibly for CARB only) installed by GM.
kpic
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LLC5
As I've never seen one, read or heard of one until Factory C3 posted which made me curious. So after a fruitless search through my library; I started searching. All I found was a couple of posts at a few different forums.
The inner filter was factory installed and one year only, 1981. The most viable claim was it's purpose was some kind of emissions component. Other reasons were backfire baffles, flow straighteners etc. Having owned a boat with a V8 the flame arrestor was nonsense and straightening flow before a 90° turn would lack any sense.
As most original owners pitched them for an aftermarket filter; they are only found on original low mileage 1981 Corvettes. Due to its function, the low mileage makes sense.
Some owners claim starting problems vanished when they replaced both filters with a K&N. After a decades of use, that makes sense also. All owners claim more power after replacing them. Amazing, how some claim to be able to feel a couple of WHP.
As the above came from the internet and we all know the internet. If anyone owns a 1981 Corvette Service Manual, I'd be interested in learning what it documents.
Hib Halverson
Technical Writer for Internet & Print Media
I'm even more convinced it's a di-inverse flow confabulator.
Antz81
Well-known member
Some owners claim starting problems vanished when they replaced both filters with a K&N. After a decades of use, that makes sense also. All owners claim more power after replacing them. Amazing, how some claim to be able to feel a couple of WHP.
As the above came from the internet and we all know the internet. If anyone owns a 1981 Corvette Service Manual, I'd be interested in learning what it documents.
Some people also believe getting rid of the computer controls gives the car more power, but we all know some people never have their buttometer calibrated.
there's no mention of this filter in the service manual. It never refers to filters, only the filter or element.
LLC5
Well-known member
LLC5
As I've never seen one, read or heard of one until Factory C3 posted which made me curious. So after a fruitless search through my library; I started searching. All I found was a couple of posts at a few different forums.
The inner filter was factory installed and one year only, 1981. The most viable claim was it's purpose was some kind of emissions component. Other reasons were backfire baffles, flow straighteners etc. Having owned a boat with a V8 the flame arrestor was nonsense and straightening flow before a 90° turn would lack any sense.
As most original owners pitched them for an aftermarket filter; they are only found on original low mileage 1981 Corvettes. Due to its function, the low mileage makes sense.
Some owners claim starting problems vanished when they replaced both filters with a K&N. After a decades of use, that makes sense also. All owners claim more power after replacing them. Amazing, how some claim to be able to feel a couple of WHP.
As the above came from the internet and we all know the internet. If anyone owns a 1981 Corvette Service Manual, I'd be interested in learning what it documents.
If it was factory installed (the more I look at the picture, the more it does look factory installed even with the blue sealant) then it probably is an evaporative emissions device required by CARB.
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FactoryC3
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Just for the looking and info, here is a link for a new assembly...78 79 80 80 81 Corvette GM Air Cleaner Assembly PT 25040289 | eBay
kpic
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As all the systems talk to the computer; a lot can be done with car "computers." Just about everything can be changed to support modifications. A processor can do a lot more than a chip. OTOH, to play one needs HP Tune and a dyno to really play.
Calibrated or re-flashed?
The picture at the Ebay link shows a double step, the filter sits where the rust (so sad) is and the "extra" is higher. Do the pictures in the manual show the same steps?
Unfortunately, manuals are for fixing, they do not communicate design intent.
The shape of the metal implies it was factory, GM paid extra for something unneeded in the die. Looking at the Ebay picture, the "secondary" filter is higher than the primary which would restrict flow. By the snorkels, the metal on the right side at the step appears to be different than the left.
It could be CARB as one of the posts I read said there was charcoal in it. :eyerole
Antz81
Well-known member
There is definitely a double step on mine with a nice flat spot for a small filter of some type.
No pictures of the air cleaner in either the FSM or AIM that show this (or any filter), so not much help there.
It does look to be factory fitted, but I've got no idea what it would be for.
xfirez51
Well-known member
The OEMs were still scrambling w emissions. All kinds of klugey stuff on motors that were legacy designs.
LLC5
Well-known member
Damn, after seeing the price of that e-bay unit, forget my suggestion to remove the inner filter assembly. If you want to run the vehicle without that double filter configuration, buy an aftermarket or used OEM filter housing without the double filter assembly and install it, and box and keep your OEM assembly. I am sure that there are many quadrajet air filter housings to choose from that don't have the inner filter unit. Good luck with it.
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