Classic Cars and The Smog Police

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It’s been more than 40 years since the federal Clean Air Act went into effect, which among other things means there are quite a few “antique” and “classic” vehicles (usually defined as a car or truck 25 years old or older in most areas) subject to emissions control laws and – sometimes – tailpipe emissions testing, too. Even after 40-plus years. California, for example, requires that all motor vehicles built since the 1968 model year (the first year pollution controls were installed on new cars) pass emissions as a condition of being able to get plates/register the thing – just like any late-model car.

Other states have a rolling retirement system under which cars are subject to emissions testing until they hit 21 or 25 – after which they become exempt from the actual sniffer tests.

But – and this is important to know – even the more lenient rolling system doesn’t exempt a pollution controlled motor vehicle (remember: That means pretty much anything built from 1968 onward) from having its original, factory-installed emissions control intact and at least seemingly operational. It may not have to pass a tailpipe sniffer test, but it will have to pass a visual once-over by the inspector. This is part of the state motor vehicle safety inspection that most states have in place, which usually includes checking off that the factory emissions stuff at least appears to be there – and working.

For example: If the inspector notices that a car originally equipped with a catalytic converter doesn’t have one, the car will fail state inspection.

There’s one possible escape hatch. Most states offer “antique vehicle” plates for cars and trucks more than 25 years old. Usually, these confer a permanent registration as well as an exemption from both state motor vehicle emissions and safety tests. But the catch is these plates are usually limited use only and issued with the proviso that the car be driven less than 2,000 miles per year (if generous) or operated on public roads only for “testing” purposes, or to go to and from antique/old car shows – if not so generous.

If a cop notices you driving to work every day in an old car with antique tags there’s a good chance he’s going to hassle you

So it’s important to think – and plan – before you make any modifications to an antique or classic car built after ’68 – and especially those built after 1974, when catastrophic converters came online and emissions equipment started to get more elaborate with each new model year. Even though the total number of 25-year-old or older cars being used as daily drivers is small and their impact on air quality negligible, “old cars” are an easy – and visible – target for do-gooder political frauds braying about “the environment” and “clean air.”

Here are some tips:

Don’t be obvious –

Things such as aftermarket chromed valve covers, an open element air cleaner and other such clearly non-stock parts on the engine will make it more likely that the inspector’s gonna look more closely at a car he might otherwise have given a casual once-over.

A side benefit is that factory air cleaners are usually big things that cover up most of the top part of the engine – neatly obscuring any mods. you may have made, or the absence of such parts as the EGR valve (which many non-factory, high-performance manifolds lack provision for). Save your factory valve covers, air cleaner and other such parts. These can be easily re-installed for inspection day – then swapped out for the good stuff after you get your sticker.

Camouflage your mods –

* Non-stock aftermarket aluminum intake manifolds can be easily disguised by painting (or powder-coating) them the same color as the engine. I used this trick on my ’76 Pontiac to hide the presence of a medium-riser high-performance intake. The aftermarket manifold looks factory at a glance and only close inspection reveals the fact that the original part is no longer on the car. Avoid obviously not-factory carburetors, too. It’s worth a little work tuning a stock Quadrajet or Carter AFB vs. pulling it out and replacing it with a double-pumper Holley.

* Reinstall all the factory fittings and hoses – even if they are just dummied up to look like they work and don’t actually connect to anything. Many older cars built from 1968 to the 1980s have milesof vacuum lines and several fittings that screw into the intake manifold and the water neck/thermostat housing. Always try to retain at least the factory look of these parts were possible.

* Avoid headers – or use legal ones. They’re e a great performance enhancer – but they’re also obvious, visually and otherwise. The presence of headers on any pollution-controlled vehicle (especially ’70s and ’80s-era stuff) is going to cause problems for you. Use headers that are legal (they’ll have a California Air Resources Board/CARB or EPA exemption) and that work with any existing pollution control equipment, such as Air Injection Reaction (AIR) tubes. They’re more expensive than the generic, one-size-fits-all kind – but they’re also not illegal and won’t cause you to fail inspection. Another very good option with certain makes and models is to use factory-type cast-iron headers. My old Trans-Am has a set of factory Ram Air manifolds. Well, they were factory-available equipment on some ’60s-era and early ’70s GTOs and Firebirds. But they fit my car like they were factory-installed – and even better, they look factory installed.

* A reasonably quiet exhaust will help your case just like wearing a nice suit to court instead of cut-off jeans and a wife-beater T-shirt. Flowmasters (and similar) aftermarket mufflers flow great and are also not-obnoxiously loud.

* Dummy cats. Early catalytic converters – especially the GM “pellet” models used on all GM cars from 1975 through the early ’80s – sucked. They crippled performance. Just cutting them out and replacing the thing with a section of straight pipe could free up 15-20 hp on some cars. But now you’ve run afoul of The Law. A simple trick is to drain the thing. Those old pellet style converters usually have a plug on the bottom that you can pry out. Then you drain the pellets. Looks right, performs better. Or, if you have a more modern “honeycomb” converter, you can cut the thing open, pull out the ceramic honeycomb inside and then bolt the two shell halves over a section of straight pipe to create your very own fake catalytic converter. It looks perfect – trust me.

The only caveat here is you can’t do the above skullduggery on cars equipped with OnBoard Diagnostics, which means most cars built from the early-mid ’90s forward. The “check engine” light will come on – and if the inspector sees that, you’ll probably fail the inspection.




  1. Curious if anyone knows much about My 92 f-250 with a 460, Emissions. I see one 02 sensor.My catalytic converter has two air tubes running to it. I read something about this helping with emissions when the engine is cold. I think maybe the old cat is getting plugged up. I am wondering what would happen if that material inside the cat were to disappear. How those air tubes/injection would affect how the truck runs.My truck is old enough that no emissions testing is required. I could make it look original anyhow.

    • Those air tubes run to a ‘smog pump’ that’s run by your belt. It pumps air to the cats. Gutting your cats won’t do anything but make a bit more power, at the cost of higher emissions and the potential for smelly exhaust. No converters also negate the need for the smog pump, which will further increase efficiency/power with a bypass. Pull it off your engine and run a shorter belt since the pump pulley will be out of the loop.

    • Those air tubes run to a ‘smog pump’ that’s run by your belt. It pumps air to the cats. Gutting your cats won’t do anything but make a bit more power, at the cost of higher emissions and the potential for smelly exhaust. No converters also negate the need for the smog pump, which will further increase efficiency/power with a bypass. Pull it off your engine and run a shorter belt since the pump pulley will be out of the loop.

      • Hi Matt,

        I had an ’80 Camaro with Air Injection Reaction system; the thing would diesel endlessly with the ignition off and the gas pedal floored – hilarious!

  2. You can use a “spark plug anti-fouler” adapter to space back the 02 sensor to keep ift from reading “dirty” exhaust..

  3. Two guys at my work removed their cats and their trucks stink like hell when they drive by. Federal law about keeping emissions in place. Just do the right thing and make your vehicle run like it is supposed to.
    I know all about how to remove and modify stuff.It really isn’t necessary.

    • Hi Ron,

      Modern car engines were designed with their emissions controls – as a complete system. Disabling or removing the emissions controls in these cars is therefore usually not a good idea in terms of making the engine run better.

      But it’s a different story with cars with engines designed prior to the imposition of the first emissions standards.

      These cars – those made circa 1968-early 1980s – had emissions controls grafted onto them after the fact. The engines were not designed to be “smogged” and the emissions systems and parts were frequently crude, inefficient and caused significant drivability problems. Removing or disabling them often resulted in much better performance, higher mileage and a better-running car.

      For example: GM’s first catalytic converter – the ones GM used on its cars circa 1975- early 1980s – were “pellet” rather than lattice/monolith style and hugely restrictive. Removing this cork in the exhaust system dramatically reduced exhaust backpressure, which improved engine power/performance markedly.

      Another: Early EGR systems clogged easily and frequently (because the engines they were grafted onto were not designed for EGR). Disabling the EGR on a car from the ’60s or ’70s was – is – usually good for the car.

      The rest of the exhaust system in cars from this era was also typically very restrictive, which choked performance and – ironically – mileage.

      My ’76 Trans-Am originally came with a single exhaust – if you can imagine that. A huge V8 (7.4 liters, 455 cubic inches) strangled by horrifically restrictive “smog” exhaust manifolds that fed into a “Y” pipe which dumped into one of those restrictive pellet-style cats and then one pipe from there to the back of the car and a pair of fake dual exhaust outlets.

      Simply replacing the factory system with a dual exhaust system – one pipe and separate muffler for each side of the V8 – effectively doubled the exhaust system’s capacity and gave a huge, immediate performance uptick. Replacing the awful “smog” exhaust manifolds with headers or factory cast-iron “Ram Air” header-style manifolds from the earlier Pontiac high-performance V8s improved things even more.

      “Smog” Carburetors were often jetted excessively lean – again, as a crude way to reduce emissions – but this made the engine run hot and not well. Richening the air-fuel ratio cured these problems.

      Most of the cars from that era have engines with extremely low compression ratios, too. Another attempt to Band Aid emissions – to make an engine designed in the ’50s (as most of the V8s used in classic cars of the ’60s and ’70s were) comply with emissions standards never dreamt of when they were designed 20 years prior to the imposition of those standards. The 455 V8 in my 1976 Trans-Am, for instance, originally had just 7.6:1 CR – which is one of the main reasons why this engine only made 200 horsepower… originally. By swapping cylinder heads with smaller chambers from an earlier, pre-smog Pontiac V8, upping the 455’s compression to a reasonable 9.5:1 or so is easily accomplished and this results in an immediate gain of 30 or more horsepower without any other modification to the engine.

      Finally, classic cars are so few in number at this point in time that whatever their emissions are, they are irrelevant in terms of any quantifiable negative effect on air quality.

  4. If all else fails move to Oklahoma. As far as I know we have no “enforced” emissions laws. I have a 70 Lemans with duel pipes muffled only by glass packs. Tons of pickups around here run straight pipes. It’s kinda like muscle car heaven. I’d assume it’d be impossible to enforce laws in a state with so many work trucks, old rat rods, and classic muscle out numbering Priuses.

  5. Just to be sure I’m clear on this, sadly enough I live in Virginia. As long as I have antique insurance on my car, along with the antique tags there’s no problem right?

    Also one small question I was wondering about, I drive my antique vehicle once every other week, a small distance. Could I drive it to work (just once) to show it to a friend without the cops busting my balls? I just don’t want to be at work and the cops hand me a ticket for it being in the parking lot. As I mentioned it’s only a one time thing, also it’ll just be for a couple hours.

    • Hi Josh,

      I’m in Va., own several antique vehicles – and here’s the deal:

      Antique tags are “permanent” – meaning, you never have to renew them, no decals, no state inspections.

      You are required to carry insurance, though, for as long as you have the plates – even if the car is not operable or being driven. The insurance can be whatever insurance you wish, so long as it meets the VA liability requirements. In other words, you don’t have to have antique insurance coverage (which is usually comprehensive and may/probably does have an annual mileage limit as well as requirements that the car be garaged rather than parked outside). You can have a standard policy. So long as you have insurance. Don;t ever let your coverage lapse without first turning in the plates to the DMV. If you don’t and they find out (they spot check) you can be in for a lot of hassle and expense.

      Now, the catch is that VA considers Antique tags “limited use.” Technically, you’re only supposed to drive the car to and from shows, for”testing” purposes and so on. (The DMV web site has all the details.) But this is not enforced unless you really make a show of driving some old beater every day and a cop notices you’re doing it.

      So, yes, you can absolutely drive it to work every once in awhile – and other places, too. Just don’t drive it every day, especially back and forth to the same place!

      • Thanks a million, Eric! That was basically everything I needed to know. I drive the car about once every to weeks, 25 miles at the most, so I’ll probably be in the clear mileage and usage wise. I just wasn’t positive on being able to drive it to work, the cops in my city look for any reason to give a person a ticket. I just didn’t want to risk getting one if they seen it at my work place, with those tags. Thank’s for clarifying this though, Ive been searching for that one bit of information for awhile now.

        • Np!

          You should be fine. One of the good things about the law is that the “testing” or “road test purposes” provision is pretty vague, so it’s hard for a cop to ticket you, even if he wanted to, unless you drive by the same cop every day, on the same road, and he sees you and has a Jones to bust you and can document that you’ve been driving the car every day.

          I’ve had antique tags on my Trans-Am for 20 years now and never had any issues, either here or in the Northern Va. area where we used to live.

          Ditto several old bikes.

          PS: One thing that’s important I forgot to mention before… the DMV will not issue you Antique tags unless you have another vehicle normally registered/tagged in VA. They’ll ask for the VIN, year, make and model and you have to sign a form to the effect that this vehicle is your daily driver.

          Here’s a link to the PDF of the form:

          Years ago, when I did not have another car (just the Trans-Am) I listed my ’83 Honda Nighthawk (which was not an antique at the time) as my “daily driver.” It’s perfectly legal to do this; a bike is as much a “vehicle” as a car.

          Just fyi…

  6. What’s the deal on antique tags in Virginia? I purchased some a few years ago and I was under the impression I would be able to keep them forever. Anyhow, in order to save some money I removed the insurance on my toy car. DMV wants their plates back, or my license.. Not possible to keep the antique tags I paid a lot for?

    • Of course they want the plates back… It’s Virginia. The reputation of that state is known far and wide in automotive circles. I could tell you they’d want the plates back 🙂

      Got a photoshop idea… the old Virginia is for Lovers slogan? Change lovers to clovers 🙂

      Clovers cannot conceptualize a car that is being kept but not used and the insurance cartel takes advantage.

      If you start paying insurance again that will likely satisify them. Just get some minimalist storage policy or something from an antique auto insurance company.

      • Dom, I got a ticket in while I still lived in the Communistwealth of Virginia for an expired county sticker (all of my other “papers” were up to date). I had been working 7-12’s and it was only out by 48 hrs. When I explained this to the cop, he said he’d only cut one person a break on a county sticker because that guy had just bought a car from his sister and was moving it to his house. I asked if the car had the mandatory county “storage sticker” on it. He responded that’s a new law. I countered with “if you call being on the books ten years new”. He was obviously pissed that I knew more about than he did and wrote me the ticket anyway.

        I took time off from work, went to the courthouse the next day and paid protection…er…I mean bought the sticker. When I went to court the cop wanted to know what I was doing there. I told him “getting your ticket thrown out”. He said “we’ll see ’bout that”. When they called me up to plead, I informed the judge I wasn’t there to plead, I merely wanted to show the court that I had *no intent to violate the law* and had complied with it as soon as the nice officer “reminded me” of my oversight.

        The judge said it could happen to anyone and told the clerk “mark that law complied with. Next case.” The cop didn’t even get to speak. I lost more money taking the day off to fight it than the ticket would have cost me, but it was a matter of principle. Virginia is For Clovers? Yep, and a nice place to be FROM these days as well. 🙁

    • Here’s the deal in VA:

      You are required by law to maintain state minimum liability insurance coverage or turn the plates in. Even if the car has antique tags and sits in your driveway all year. If it has tags, it must be insured. They check – at random – and if they find you don;t have insurance they will ass-rape you like Mr. T on meth. Bad, bad scene.

      The good news is that antique vehicle coverage is not necessarily that expensive, in part because it is based on limited use. Some policies also have provisos for project cars. I’d call around and see. I have an “agreed value” policy on my TA; costs me I think $250 a year.

      The other option is to just turn in the tags. Or better yet, don’t ever title the vehicle in your name. This will save you the multiple DMV fees, too. I finally wised up and stopped titling certain vehicles that I have just for looking at (mostly). Screw the bastards!

  7. Just a word of extra caution about driving a car in California that hasn’t been put through smog inspection to COMPLETE the registration process; if it exceeds 6 months past due the state can seize the vehicle once you get pulled over. This seems to be something alot of people I’ve talked to don’t generally realize. I myself only found this out when I had to use my truck as a means to get to work when my other car broke down due to a bad alternator that would cost over a hundred dollars. I had paid registration fees and have insurance on the truck but hadn’t dealt with the smog inspection because finances have been really bad, and smog requirements are strict. I’m doing the paycheck-to-paycheck thing, so gas wise it also would cost me too much to use it daily, but when the other car broke down near the end of the month I figured I would just bite the bullet with facing a possible citation that I can ‘pay later’ and take it on the road just for that week to make rent because carpooling wasn’t an option for me. I didn’t know what kind of chances I was taking, and with a tag 8 months past due I definitely got pulled over, but was given a huge chance by a frustrated police officer who told me I needed to take it straight home and leave it there or else it WILL BE SEIZED the next time I get pulled over. I owe him a world of gratitude because the truck in question is extremely sentimental and was my first car, I’ve had it for 15 yrs. I can only assume someone else out there is probably grappling with the same decision for similar reasons, and when I’m either on my way to work or coming home I sometimes see cars that are expired almost to the 6 month mark. Hopefully this helps somebody.

    • It’s outrageous, isn’t it? Another assault by the powers that be on ordinary people just trying to get by (and not harming or even bothering) anyone. Consider: Someone such as yourself stands to be robbed of their vehicle at gunpoint – by the cops, by “the law.” Meanwhile, these same cops (and “laws”) are too lazy/indifferent to do anything substantive about violent predators, a recent example being that Phillip Garrido character. Multiple sex offender, on parole, but the cops couldn’t be bothered to check out his house (which they had a legal right to do because he’s a convicted felon and on parole) where he imprisoned that girl for something like 17 years. Even after neighbors called to complain about what was going on.

      Too many out-of-date registration stickers and speeeeeeeeders to worry about, I guess.

      • Thats not true. You are harming the environment! They have smog laws for a reason, and CA has bad air quality already. I have a 76 g20 that is having issues passing smog only because it is missing an egr valve and cat. Passes emissions clean but they still want that stuff on there. Yes its a pain in the ass to deal with, but so is trying to find clean air to breath.

        • Hey Joe,
          If your g20 “passes emissions clean”, then how does that “harm the environment”? This is the whole problem with California’s smog check program. You can be blowing zero’s out the tailpipe but the state doesn’t care about that. If you’re missing this, this or that, too bad, you fail. They’re only concern should be what comes out the tailpipe, there’s no reason to open the hood.

          The amount of old cars on the road is so insignificant that it doesn’t hinder your quest to “find clean air to breath”.

          • Hi Adam,

            You bring up an excellent point. The only relevant criteria as regards smog is – should be – whether the vehicle meets the applicable standard for the model year. Not how it does so. Not whether it has been “modified.”

            I have no doubt that – as an example – my ’76 TA would be cleaner at the tailpipe with a dual exhaust system and a pair of high-performance monolith cats vs.the stock (POS) GM pellet cat. But this mod would cause the car to fail smog, regardless of its actual emissions output.

            Which, of course, is absurd.

  8. Actually much of the same is done on cars with OBD1 and OBD2 systems.

    A common need for the use of high flow catalysts or for removing the catalysts out right is to put in resistors that mimic the signal of the aft O2 sensors. The computer doesn’t know the difference and thinks there is a working catalyst.

    Headers, so long as the forward O2 sensors can still be fitted they will work fine as far as the car is concerned. Intake manifolds are often changed. A common mod is to fit ’96-’98 mustang 4.6L with a ’99 up PI intake manifold without swapping the heads. Of course the proper solution is expensive because of the coolant passage change… but the kludge is glob of RTV… not something I’d do to my car. There’s a GM engine where one can modify a plastic intake or use an aftermarket dorman one with modifications.

    There are also modifications to to on the air intakes, throttle bodies, fuel injectors, etc. People figure out ways to deal with the sensor issues. Of course the ultimate solution is to alter the programming, which is done as well.

    Of course any mod of the emissions system on a 80s and up car has to be done with more care because these systems are made to work with each other. Just taking off or disabling emission controls can often hurt performance all around while on a ’70s car the stuff was all tack on so removing it was almost certainly an improvement.


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