By on March 1, 2019

1979 Dodge Truck Brochure, Image: ChryslerTTAC Commentator Nate writes:

I’m working on a  with 360CID V8 4BBL carbureted engine, automatic trans, , EGR valve, and charcoal canister for the fuel tank hydrocarbons. The underhood factory decal says “California Medium Duty Emissions” and it has no catalytic converter from new. So here’s my situation:

  • All hoses, pipes etc. are there and all valves etc. are working .
  • The A.I.R. pump works but the diverter valve has failed (vacuum diaphragm leaks) and is in the open position so it’s always blowing fresh air into the exhaust manifolds.

Is it likely to pass the emissions test like this? I took my Ca. smog tester license training in 1984 and honestly only remember bits and pieces. So far I’ve not been able to find a new or good used diverter valve. Please advise!

Sajeev answers:

I know you’re a handy guy, so let’s assume the other items are sorted: horn/all lights work, good brakes, legal tires, carb is tuned up, fresh spark plugs/wires/filters, etc.

You should sail past the emissions test because — as you suggested — a medium duty, 3/4 Ton truck in 1979 (or even 1/2 tons ?) rolled out of the factory lacking a catalyst. I can’t find where such a vehicle fits in , if it was ever sold/registered in California in the past, odds are its emissions testing bar is set low! Check out the “evaporative” section , there’s a chance you just need a functioning charcoal canister with intact rubber hoses!

I reckon it’ll be just as they say about any pre-1975 vehicle: nothing!

As a bonus, considering the air injection reactor pump (smog pump) is stuck in “lower emissions” mode (i.e. always thinning out the exhaust with fresh air) you should pass with flying colors. Granted, those colors are dirty shades of brown with shameful amounts of that , but an emissions-exempt antique is a historical relic and not a menace to urban living.

Good luck finding another diverter valve! After working on a buddy’s 1991 Ram 150, finding several body and (Central) Fuel Injection components were shockingly impossible to procure from the usual places.  Certainly not impossible with a few calls to the right junkyards, but your high malaise-era emissions equipment? That’s a totally different kind of pain: I recommend making its part number a saved search in eBay. 

[Image: Chrysler Corp.]

Send your queries to [email protected]com. Spare no details and ask for a speedy resolution if you’re in a hurry…but be realistic, and use your make/model specific forums instead of TTAC for more timely advice.

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37 Comments on “Piston Slap: An Emissions Digression, Dodging Diverted Air?...”


  • avatar
    Jon

    I got my 77 SBC to pass emissions by running a 70/30 mix of gasoline and denatured alcohol when testing. Alcohol burns very clean (a lot cleaner than gasoline). Retard the timing a lot since alcohol burns much faster than gasoline. The engine will lack power when driving to the testing center but will run very clean. An air diverter valve that is stuck open wont matter if the engine is running super clean. Denatured alcohol can be found at any hardware store.

  • avatar
    87 Morgan

    Wow, working on a Mopar 360, awesome! I have driven several examples of that motor and have always come away in awe of how much fuel that engine can burn. My in laws had a Jeep Grand Cherokee (think ‘Breaking Bad’) for awhile 25 years ago and wow that could thing chugged fuel in a similar fashion to my 502 CID powered Chevelle. Great engine though, smooth and will last a very long time.

    Best of luck getting it to pass emissions!

    • 0 avatar
      jatz

      “my 502 CID powered Chevelle”

      Wow… that took me back. Vietnamization and Santana. Checked online and restored ones seem to hover around 60K.

      Then up popped one, also seemingly clean, asking 15K.
      It has an AT. Does that kill value so hugely?

      • 0 avatar
        87 Morgan

        I think Autos are worth more in the end. If you are not familiar with a Muncie Rock Crusher (though mine had a Richmond Super T10 which is no easier than the Muncie), than you will be sorely disappointed…Civic 6 MT they are not. I think they use a clutch spring from a Kenworth, I could be wrong on that but I doubt it.

        I had a 72′ Chevelle which I kind wish I had not traded it off which is another story. For 30k or less you can find yourself a very nice resto modded Chevelle (not a legit 70 454 LS6 car of course) that will bring a smile to you every time. Mine had a great suspension ice cold AC and a radiator that came out of a nuclear submarine so you could tool around in the summer heat of 100 and never overheat.

        My oh my the 502 is a torque monster, it was such a blast to drive when you squashed the pedal it was like someone had their foot in your gut pushing you back into your seat. I love that feeling, hence I am not the ‘Miata is the answer’ guy, but to each their own.

        • 0 avatar
          PrincipalDan

          Dear Ol’ Dad had a 396 SS back when I was still in utero.

          Back in those (late 70s post gas crisis) days it was really just another used car. But I credit it for giving me part of my auto enthusiasm even though it was sold off before I was born.

          Mom hated it because she couldn’t control it in the snow.

        • 0 avatar
          jatz

          “Mine had a great suspension ice cold AC and a radiator that came out of a nuclear submarine so you could tool around in the summer heat of 100 and never overheat.”

          God, what a retirement ride for when MPGs don’t matter.

    • 0 avatar
      Lorenzo

      Funny that Chrysler had a 360 cid engine from 1971 to 2002, but when it bought AMC in 1987, it continued to use the AMC 360 engine in the “Grand” Wagoneer, until 1991. If your engine ever needs parts, be careful you’re getting parts for the Mopar, not the 1988-91 AMC 360. FCA may have parts for both, and they’re not the same engine.

      • 0 avatar
        -Nate

        Thanx ! .

        It runs very strongly, a rebuilt engine has been fitted *just* before the salvage auction, I’m pretty sure some CalTrans employee was planning to buy it (a common occurrence) but then they had the San Fransisco earthquake in 1988 and about 3/4 of the salvage vehicles were yanked for emergency duty, this one being a _filthy_ service bed, wasleft in the auction, no CalTrans employees were present at the auction, also a rarity .

        Hopefully it’ll last until Tom’s done with it, he bought a Mercedes Benz OM603 3 liter i6 Diesel engine and four speed automatic tranny in case we ever find someone qualified to install that .

        -Nate

  • avatar
    jatz

    “my 502 CID powered Chevelle”

    Wow… that took me back. Vietnamization and Santana. Checked online and restored ones seem to hover around 60K.

    Then up popped one, also seemingly clean, asking 15K.
    It has an AT. Does that kill value so hugely?

  • avatar
    Flipper35

    When I brought my built 360 to CA it was a nightmare. Timing was not correct for emissions, the carb had a linkage from a Chevy because I had rods instead of a cable so that didn’t pass (the carb was for a Mopar, just the linkage on the side of the shaft was different. All sorts of stupid stuff. They never did actually test the emissions.

  • avatar
    MBella

    Since you’re in California, if you have any issues, find a test center that’s more “accommodating”. They’re private so you should be able to find one in your area.

  • avatar
    Yankee

    I agree with Sajeev that your truck will likely pass. However, if it doesn’t, you may have other recourse. Every state is different, but here in PA (where new vehicles have had to conform to California emissions specifications for decades now and testing varies in stringency based on the population density of the county of registration), there is a provision for a “part exception” for emission control parts that can no longer be obtained. All the consumer has to do is document an attempt to obtain it from the original manufacturer (e.g., dealer parts department) and one aftermarket source, and they will be given an emissions sticker with an “EXEMPT” insert on it. Your testing center should be aware of the applicable regulations. Kudos to you for trying to do the right thing, and best of luck with your project!

  • avatar
    Rasputin

    As corrupt and bankrupt (they go together) as my State of New Jersey is, it did something last year that I liked. I received a letter stating that I no longer had to bring in my 1993 Lincoln MkVIII for emissions testing as it was now 25 years old. Only 2 more years to go for my 1996 Miata.

    BTW, sometime about 10 years ago, NJ stopped with safety inspections, but it continued emissions inspection. The ideologues in the Statehouse care more about Gaia than they do their voting, taxpaying citizens.
    Cannot wait to leave this s***-hole of a State.

    • 0 avatar
      MRF 95 T-Bird

      My 1995 Thunderbird MN-12 V8 registered in NYC has been emissions exempt for the past few years. I did have it checked a couple of years ago and it still runs clean. Just the full safety check for $23.

    • 0 avatar
      87 Morgan

      Grew up there. Packed up my stuff in 1994 moved west for college.

      I visit now, less and less often…..We used to covet the pink cards you would get when your car failed inspection, the key was to keep them out of the sun so they would not fade as the cops would notice a faded one and know you were past due on the 30 day extension they pink card on the dash denoted.

  • avatar
    pwrwrench

    “Since you’re in California, if you have any issues, find a test center that’s more “accommodating”. They’re private so you should be able to find one in your area.” MBella is correct. Try to find a shop that works on “old” American vehicles and or does restorations. They could probably refer you to a test station.
    On the books the test tech is supposed to verify that all the emission hardware/devices are there and functioning before the exhaust test. I doubt that there are many test techs with much experience with 1970s vehicles so they will just go with what is in the “book”. Results can vary.
    As someone mentioned there is probably an exemption for non-functioning parts that are not available. Go to the Bureau of Auto Repair website and see if they have that info.
    The periodic vehicle emission testing in most States is a slight of hand, wink-wink, “I see nothing” thing. Part of the Federal Clean Air Act is that States that do not (did not) meet the air standards would not get Federal Highway $$$. The initial time limit was around 1980. California was not going to meet the air standards and cutting off Highway $$$ would cause a huge disruption in the economy based on building more tract houses and the freeways to reach them.
    That’s where the bi-annual testing comes in. Carefully crafted computer models make it look like ‘progress towards clean air’ is being made and the Federal $$$ still flow.
    Don’t misunderstand, the air in most of California is better than it was in the late 1970s. That’s mostly due to vehicles being manufactured with design/engineering that is better than the 1960s and 1970s. The testing/maintenance/repair program plays a very small part in that.

  • avatar
    PrincipalDan

    Reminds me of that time that my Dad test drove a private party sale 1984 Toronado that had the emissions equipment disconnected.

    He ultimately passed on the car because he was afraid what the seller might be hiding. I don’t remember any noticeable difference in power over any other 307 Olds V8 but I do remember the isolation in the ride quality.

    • 0 avatar
      MRF 95 T-Bird

      I owned a 1980 Toronado diesel that I bought from a neighbor in the late 80’s for a mere $500. It even had a replacement Goodwrench motor under warranty. 28 mpg highway and great isolation in the ride quality lasted for a couple of years until the motor made death rattle sounds. I sold it to someone who wanted to do a gas 307, 350
      Rocket V8 conversion.

      • 0 avatar
        PrincipalDan

        I really like that generation of Eldorado and Toronado (lukewarm on the Riviera) and would love to have a 1979 Toronado when the Olds 350 with the 3-speed auto was still an option. A pretty bulletproof combo before they cheapped out on displacement and the transmissions became more fragile.

  • avatar
    Felix Hoenikker

    Does CA have an emissions exemption for low annual mileage? Here in PA, cars and light trucks driven less than 5000 miles per year are emissions exempt. You still have to get a sticker each year, but that is done as part of the mechanical inspection that applies regardless of annual miles. They charge almost as much for the exempt emissions sticker as for the real one which keeps the money flowing to both the inspection station and PENDOT. I used this exemption with cars that would easily pass emissions testing based on the OBDII codes just to save a few bucks and keep the station honest.

  • avatar
    VWGTI

    “the air injection reactor pump (smog pump) is… always thinning out the exhaust with fresh air” is not true. Th air pump is supplying extra oxygen to burn off any leftover hydrocarbons. If it doesn’t shift to dump or downstream, the manifolds can glow red hot under heavy load/rich conditions.

    • 0 avatar
      Jon

      How is this possible if the air is injected after all the burning has already taken place? Not trying to be a jerk. I came here to learn today.

      • 0 avatar
        Jagboi

        If the engine is running rich for example (and running rich hides lots of sins on a car with a carb) then there is unburnt fuel in the exhaust. Adding extra air via the air pump burns off the unused fuel in the exhaust. Works particularly well with a catalytic converter, that is one of their main functions is to burn the unburnt fuel from the engine (and there is always some).

        • 0 avatar
          Jon

          I understand the engine running rich part. What i dont understand is how the extra fuel is burnt off when combustion has already taken place (ceased). Unless you mean that combustion occurs inside the exhaust manifold? If so, what mechanism starts/ignites this combustion.

          • 0 avatar
            Jagboi

            In the exhaust manifold, or a catalytic converter if equipped. That’s why the cats get so hot, it’s from the fuel burning inside. The ignition in a catalyst is a combination of heat and the precious metals in the catalyst, those start the reaction at a lower temperature than the usual ignition temperature. In the Dodge case, it’s heat alone.

          • 0 avatar
            VWGTI

            Everything is there to complete the fire triangle: fuel, oxygen, and plenty of heat for ignition. Combustion occurs in the exhaust manifold.
            The catalytic converters on rich-running carbureted cars would also glow red-hot and occasionally ignite rustproofing or sound deadening materials on the underbody. In extreme cases, carpeting would smolder/catch fire.

          • 0 avatar
            Jagboi

            Autoignition temp of gasoline is around 220C, depending on the exact blend. I have put an exhaust temp gauge on one of my cars and on a long mountain grade it went off scale at 1100C. Regular highway cruise was typically in the 500-600C range with the AFR set to 14.2:1 (slightly rich), so plenty hot enough to burn fuel in the manifold.

          • 0 avatar
            SPPPP

            Jon, the combustion process is never perfect. There’s also a question of partial combustion. For example, we know that burning a hydrocarbon produces carbon dioxide and some carbon monoxide. Well, why did some of that carbon join with TWO oxygen atoms, while some of that carbon joined with ONE oxygen atom? It’s basically that there wasn’t a perfect air-fuel ratio, or enough time, or perfect fuel mixing, to let the combustion process complete. What that actually means is that carbon monoxide is flammable! You already burned the air and fuel, but now you can burn the exhaust. It’s like the gaseous equivalent of charcoal. (One reason that backdraft explosions occur in firefighting.) So yes, there is some amount of combustion occurring in the exhaust of a normally-functioning car.

          • 0 avatar
            pwrwrench

            Air injection into the exhaust, whether by pump or through reed/check valves, is to get more oxygen.
            As has been mentioned some of the oxygen helps to burn fuel that has not burned in the combustion chambers. The latest engines with computer controlled FI and ignition and better cylinder head design are better at this than an engine from the 1970s. Still some fuel goes out the exhaust. That’s what the catalytic convertor is for. It also lowers CO (carbon monoxide) by joining oxygen to the CO molecule making CO2. Some of the O2 comes from part of the CAT that breaks apart oxides of nitrogen.
            Hence the term 3 way CAT.
            With the air injection more oxygen is available for this, including the reduction of CO out the exhaust by making some of it into CO2.
            I have not seen any vehicle built for the USA since the 1990s with air added to the exhaust, but there might be a few.
            Some car makers used the air injection to avoid adding catalytic convertors for 5 or so model years. Probably saved them some production cost, but the vehicle owner had to pay for servicing the system. The check valves and diverter valves would fail and sometimes the pump. That could be expensive at emission test time.

  • avatar
    cimarron typeR

    I feel for folks with emission tests.Lucky here in KS. My first aftermarket SC’d E36 required an “inspection” because I bought it from a pleasant guy from South Dakota. It passed with flying colors. The visual inspection passed with flying colors because it had a catalytic converter and matching VINs,never mind the blower apparatus hangning of the crank without any C.A.R.B. testing/documentation done by ESS (s/c kit man.)
    I have to admit some cars really should go through inspection. I’ve seen cars with literally no functioning brake /tail lights here in KS, spewing black smoke Beverly Hillbilly style.

  • avatar
    -Nate

    3.1.19

    O.K. guys ;

    It’s a 1977 model year and so needs smog testing , no way to avoid it .

    It came with a small catalytic converter in the single exhaust, right under the cab of course .

    8,100# GVW so it’s a medium duty truck with heavy duty emissions .

    I have some photos of the FUGLY beast ~ it’s a factory crew cab with long bed service bed, all steel of coure, CalTrans ordered it to service sprinklers along the freeways up North so that’s why it’s 8,100 # GVW ~ it has Bendix duel servo oversized (3-1/2″ X 12″) brakes on it too as it’s HEAVY .

    I’m not allowed to post photos, maybe Sajeeve will .

    The A.I.R. pump injects fresh air (oxygen) directly into the exhaust manifolds, the hot exhaust gases leaving the engine are well over 1,000 degrees F and *instantly* begin to combust, in the _EXHAUST_MANIFOLD_
    -not- the catalytic converter .

    Anyone who owned an 1967 ~ ’72 Chevy remember those wretched steel tubes sticking out that rusted away and also the glowing red exhaust manifolds ~ Chry – Co has a similar system that only has one steel pipe going to each exhaust manifold, it goes to the rear of each exhaust manifold and there are passages to direct the fresh air .

    All that works, I did find an NOS diverter valve (Chry-Co cheaped out and bought some obscure GM Rochester 6 cylinder diverter valve) .

    I also was able to find a rebuilt A.I.R. pump and installed it .

    These small block engines originally came with the over engineered CARTER Thermoquad 4 barrel carbys, an O.K. carby *except* for -two- things :

    The bowls were made of Phenolic PLASTIC FGS, this on super hot running smog choked V8 engines so guess what happened to those plastic float bowls ? . yep, they died, in droves .

    The second thing was : you needed a flow bench to adjust the vacuum operated fuel metering rod making it impossible for any regular shop to adjust/service/overhaul/rebuild it .

    In 1986 I found every last one of those plastic float bowls I could in America and order them for the old Dodge & Plymouth Cop Cars of L.A.P.D. .

    So, this truck was originally owned by CalTrans, our state highway department and when the original Thermoquad carby died they bought and installed a HOLLY # 4165 dual bowl, progressive 4 barrel carby that’s specifically designed and C.A.R.B. approved for this application and ever since we bought it the truck has whistled though the smog tests, this time when I got it running, fuel was spraying out the bowl fuel transfer tubes so Tom had me remove the carby and he took it somewhere I didn’t know to have it rebuilt, they handed it back looking all clean and spiffy, I installed it and that’s when the troubles began .

    The shop that rebuilt it, didn’t do smog tests so why the hell he chose them I have NO IDEA ~ as usual, everything goes to shyte and then I get the call to fix it .

    At this point I’ve replaced the E.G.R. valve and spent an entire day hand digging 40 years of carbon buildup out of the E.G.R. passages in the intake manifold, replaced the distributor that had a ruptured vacuum advance unit, cap, rotor, wires, spark plugs, electric choke heater, vacuum delay switch, amplifier and about 15′ of vacuum hoses, the charcoal canister is present and has hoses connected, I make a point of using spring typ hose clamps on _every_single_ danged hose connection (it’s actually an A.Q.M.D. rule no one else cares about), the brake booster because it too had a ruptured diaphragm and was whistling like a teak kettle and the engine idle improved when I pinched off the booster’s vacuum hose, then of course the brakes failed, that’s another misery I’ll cover later if you’d like .

    Somewhere during all this the carby decided to begin running rich, like 10X richer than it should ever, I stopped working on 4 barrel carbys in 1984 and never was really happy to touch them, now I’ve taken the truck to quite a few “old car specialist’ garages and they always give me the Okey-Doke ~ my brother is so pissed off he’s spitting nails and although the truck runs really well now, it’s _WAY_ too rich both at idle and cruise .

    The guy who blew me off to – day said “I scoped it and every thing is *perfect* _but_ the carby and that’s not the original Thermoquad and isn’t leagal so I won’t touch it .

    I’d told him it was a replacement HOLLY before taking it to him) .

    Jeezo-Peezo ! I’ve been scraping petrified rocker box gaskets and hand dressing their bent lips after hand cleaning off FORTY YEARS of accumulated burned on oil & grease, re painted them, I’m fixing things on this old beater but it _still_ refuses to run cleanly ! .

    GAH .

    Thanx for reading, this is the short version oddly enough ~

    -Nate

  • avatar
    ryanwm80

    How would an emissions inspector know if that part is working or not? I don’t think they would know. They’ll do a visual inspection to see that everything is in place, and they’ll check the ignition timing, and they’ll do a quick test, and as long as the emissions are within limits then it should be OK.

  • avatar
    HotPotato

    California used to have a 30-year rolling exemption but apparently it was finally frozen at “pre-1976.” But IIRC there are some exemptions available e.g. if parts can’t be found or repair would be ruinously expensive.

    I think they should just go back to the rolling exemption; it’s more sensible than a fixed cutoff in terms of parts availability.

  • avatar
    R Henry

    If all smog control devices are present, AND emissions are within spec, you will pass. The pass threshold for 1979 medium duty trucks is VERY low. The inspector is VERY unlikely to notice that failed component.

    Does your truck backfire ALOT on decel, as my old Nova did with that failed valve?

  • avatar
    -Nate

    You are correct however, I can’t find anyone who’ll touch the Holly 4165 carby, it’s leaking a little bit out of the rear bowl, my brother did some OnLine research and Holly says this leak is common and normally caused by incorrect, too high float level .

    California’s AQMD is very vigilant about hassling smog test stations looking for reasons to yank their licenses, once I find someone who’ll take the carb apart, repair it , re install and adjust so it passes the tail pipe test, I can take it to a test onlty station and it’ll fly through .

    My brother who’s no mechanic, decided to make a problem out of this instead of letting e handle it so it’s all moot for the moment .

    -Nate


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