This is probably ridiculous question but I can't seem to find a chart on google that explains typical parts of a classic american car. I always seen that round disc like cylinder on top of many muscle car engine . what is that called? PS - I am no mechanic just curious. thanks

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    Air filter....?
    – vini_i
    Commented Aug 1, 2016 at 0:37
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    The answers are correct that this is the air filter housing. Just a minor aside, this is in no way limited to Muscle car engines. My first car, a 1986 VW Polo had one of these. I liked the car, it's ~55BHP 1.3 litre engine made it a lot quicker than the 800cc and 1.0 litre cars most of my classmates had, but it was in no way a muscle car. Commented Aug 1, 2016 at 10:42
  • Almost every carbourated car had these (which was nearly all of them in the 70s and 80s) and even some fuel injected cars had them.
    – coteyr
    Commented Aug 1, 2016 at 14:53
  • ...and before the 70s and 80s. Commented Aug 1, 2016 at 20:37

4 Answers 4


You're talking about a classic air filter housing.

Older style air filters were round in shape and sat inside a round metal enclosure.

This is a Holden straight 6 from the 80s, where the air filter element is housed and sits on top of the carbeuretor.

An example from an Aussie classic - the Holden 202

It's interesting to note that even modern cars, the check engine light still has a silhouette of an classic shape engine with the air filter sitting on top.

Modern CEL

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    Whoa. +1 because I just learned something new about the check engine light.
    – Jason C
    Commented Aug 1, 2016 at 0:49
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    @JasonC Whoa me too, which is ironic because it's part of my company logo. I guess we just mentally took it for granted. The TPMS icon still leaves me a bit baffled.
    – SteveRacer
    Commented Aug 1, 2016 at 3:12
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    @Steve Richard Oakes Nice post, but I object to that AMC 199ci in what is probably a Gremlin implied as a "muscle car". Kidding. Nice post. I do find it curious that the Air Cleaner decal is labeled in "Liter" ... that has to be the late 70s, the end of AMC.
    – SteveRacer
    Commented Aug 1, 2016 at 3:18
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    Its an Australian car hence litres. Commented Aug 1, 2016 at 3:20
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    OP has it wrong in thinking they were only installed on muscle cars. Many engines had air filters like that. Unless you think a huge 130 HP or whatever power these cars had is "muscle". I think the pic is a Commodore. Commented Aug 1, 2016 at 3:27

As stated it's a circular air filter. It's positioned there because it sits on top of the carburetor. Modern cars rarely use circular air filters, they are usually square or rectangular and are connected to the air intake system by tubes.

It isn't just musclecars which used this configuration, it was extremely common on carbureted engines.


For the sake of completeness: let me add that even some VW models of the 70-80 and 90s were equipped with circular filters, the Motronic (no carburator but pre mixing of fuel and air) occasionally used them. But on the contrary I own an 1991 semi electronic carburator powered VW Rabbid (Golf) MK 2 which has a square air filter. Motronic: Seat IBIZA with VW 1.3L (1993) Motronic: Seat IBIZA with VW 1.3L (1993)

Carburetor: PN Engine, electronic carburetor, square air filter, 1.6L, 69hp (1991) PN Engine, electronic carburetor, square air filter, 1.6L, 69hp (1991) Images from car sales websites for demonstration purposes only.

I can only post 2 regular links, so here is the third: Carburetor: MH Engine of Rabbid MK1/MK2 (1987), 1,3L/54HP (http://) https://i.sstatic.net/omEmu.jpg


It's relative to whether the engine uses a carburetor or has fuel injection. The round air filer housing sat on top of a carburetor where the gas and air are mixed before going to the cylinders. Newer cars use fuel injection and the plumbing for the air flow is different. The air usually goes through an airbox where a flat, square filer is in place. The fuel is then injected into the air flow (throttle body) or directly into the cylinders (a better design).

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