Emissions in Colorado
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Junior Member
Joined: Mar 2011
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From: Colorado
Car: 84 trans am
Engine: 305ci. (lg4)
Transmission: t5
Axle/Gears: stock 10 bolt.
Emissions in Colorado
I just recently swapped a 350 into my 84 Trans Am. I am trying to find a way around emissions. So far I have found no luck in registering the car in a county that is emissions exempt. In order to do so you must have a permanent residence, you must revive mail there, it cannot be a po box, and the particular DMV I went to requested that my drivers license reflect the address where I want to register the car. Is it possible to create an LLC out of state and register the car there without having a residence? I am open to any ideas at this point. The car will not likely be able to pass emissions, there must be a way around this...
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Junior Member
Joined: Mar 2011
Posts: 11
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From: Colorado
Car: 84 trans am
Engine: 305ci. (lg4)
Transmission: t5
Axle/Gears: stock 10 bolt.
Re: Emissions in Colorado
It is not possible for the car to pass. I would like to enjoy the labors that went into this hobby. As a recreational vehicle I feel I should be able to drive this car. I am currently perusing a legal route to be able to drive this car. So yes, I am "obeying the law". If you would like to debate the logistics of the Colorado emissions program (air care Colorado), I can do this all day. Does anyone have any real advice?
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Joined: Sep 1999
Posts: 3,016
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From: Colorado USA
Car: '83 Firebird (T/A Clone)
Engine: 350 with L-69 components
Transmission: 700R-4, 2000 RPM stall converter
Axle/Gears: 10-bolt/3.73 ..
Re: Emissions in Colorado
We don't have emissions testing in my county. Colorado air is so clean that it's unnecessary.
It's all about revenue...
It's all about revenue...
Thread Starter
Junior Member
Joined: Mar 2011
Posts: 11
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From: Colorado
Car: 84 trans am
Engine: 305ci. (lg4)
Transmission: t5
Axle/Gears: stock 10 bolt.
Re: Emissions in Colorado
That is all they are concerned with, its just a money maker for the state. Unfortunately I cannot get collector's plates, only 73 and older can get collector's plates with a one time emissions test. 74-84 can get collector's plates with an emissions test every 5 years, but you are limited to driving only 4500 miles a year. I probably wouldn't drive it more than that anyway. I don't understand how a 32 ford with a v8 that has zumies on it can drive around town all summer? I see so many open header cars throughout the year at car shows and at the race track that are street legal, how is this possible?
Joined: Sep 2005
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Car: Yes
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Re: Emissions in Colorado
Why is it "not possible for the car to pass"? Exactly WHAT are they looking at that identifies it as "fail"?
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Car: 89 GTA ASC Conv., Prev: 89 GTA 6.3L
Engine: 5.7L L98 TPI
Transmission: 700r4 Automatic
Axle/Gears: 3.27:1 w/ JG1 Options:B2L, N10, U1A
Re: Emissions in Colorado
States like Montana and others will have LLC in a box programs, mostly for car tax issues. Emissions could be another angle, I suppose.
But why not just get the car some emissions equipment and move on? Less expensive in the long run, or sell for a newer, more powerful model, or put the emissions controls back on.
Colorado, with the roadside emissions monitors all over metro Denver would worry me if I was running dirty. But what's the real issue here? Not the fact it's a 350 vs. 305.
But why not just get the car some emissions equipment and move on? Less expensive in the long run, or sell for a newer, more powerful model, or put the emissions controls back on.
Colorado, with the roadside emissions monitors all over metro Denver would worry me if I was running dirty. But what's the real issue here? Not the fact it's a 350 vs. 305.
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Thread Starter
Junior Member
Joined: Mar 2011
Posts: 11
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From: Colorado
Car: 84 trans am
Engine: 305ci. (lg4)
Transmission: t5
Axle/Gears: stock 10 bolt.
Re: Emissions in Colorado
It has open headers, it now has a 350 with 10:1 compression opposed to the factory 305, I have no egr, efe, air pump, catalytic converter, pcv valves, evap, charcoal canister or any of the valves that came with. They want to see most of this for visual inspection. I was able to pass a few times with the 305, but most of that stuff wasn't actually hooked up. I had to run higher ethanol fuel, we de-tuned the carb to run like crap while getting the numbers as close as possible on a 5 gas analyzer, I deliberately loosened my exhaust flanges to create an exhaust leak, and the number one trick that actually got it to pass was the use of a cool can which we filled with ice immediately before going through emissions. When I sold the 305 I sold most of these emissions controls with it. I was talked into doing this build with high hopes that it would be possible to not require emissions. I got tired of going through the headache of getting it to pass every two years, I spent thousands of dollars, yes thousands of dollars getting it to pass emissions!
Thread Starter
Junior Member
Joined: Mar 2011
Posts: 11
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From: Colorado
Car: 84 trans am
Engine: 305ci. (lg4)
Transmission: t5
Axle/Gears: stock 10 bolt.
Re: Emissions in Colorado
Yes, the 305 had 8.5:1 compression, the new 350 has 10:1 compression. Higher combustion pressures typically leads to higher combustion temperatures which leads to higher nox emissions. Not only that but because of the difference in displacement there is more exhaust coming out then there was with the 305 due to change in volume. It would be very difficult to get these numbers identical to the readings for the passing 305. I deliberately got rid of all emissions controls when I saw the 305 so that I wouldn't have to deal with that headache anymore, it cost me too much money getting the car to pass every 2 years with the tuning necessary. I would prefer not to sell the car, I have been working on it for the last 6 years. I would just like to drive it. The V belt pulley kit I put on there is not able to accommodate a smog pump either. I could take the chance of spending a lot more money to have an exhaust done and put all the emissions controls on only to find out it may not pass.
Joined: Sep 2005
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Car: Yes
Engine: Usually
Transmission: Sometimes
Axle/Gears: Behind me somewhere
Re: Emissions in Colorado
OK, so your problem is open headers, and "deliberately got rid of all emissions controls", not 305 vs 350.
They don't test compression, do they? Do they look up block casting #s? I doubt it; not even California does that.
Put an exhaust system on it and put the emissions devices back on it. Most especially the catalytic converter and smog system but also all other visible things that will cause you to fail the visual inspection to whatever extent they visually inspect cars there. Put the tune back like it belongs and run normal fuel in it, and it will probably pass just fine. You'd be amazed at how eeeeeeezy it REALLY is to get a car to blow the numbers on the dyno.
Sounds like overall what you ACTUALLY DID was to spend a whole bunch of money unwisely and ended up turning your own cash into a weapon to shoot yourself in the shorts with. Not sure why you're coming here complaining about your poor decision-making and expecting sympathy for it. Consider it as a growing-up and learning experience. Then do your research BEFORE spending money on stuff that you can't use the next time you take on a project like this.
Don't allow yourself to get "talked into" spending your hard-earned giga$$$ on stuff that you don't have independent verification of the value of.
They don't test compression, do they? Do they look up block casting #s? I doubt it; not even California does that.
Put an exhaust system on it and put the emissions devices back on it. Most especially the catalytic converter and smog system but also all other visible things that will cause you to fail the visual inspection to whatever extent they visually inspect cars there. Put the tune back like it belongs and run normal fuel in it, and it will probably pass just fine. You'd be amazed at how eeeeeeezy it REALLY is to get a car to blow the numbers on the dyno.
Sounds like overall what you ACTUALLY DID was to spend a whole bunch of money unwisely and ended up turning your own cash into a weapon to shoot yourself in the shorts with. Not sure why you're coming here complaining about your poor decision-making and expecting sympathy for it. Consider it as a growing-up and learning experience. Then do your research BEFORE spending money on stuff that you can't use the next time you take on a project like this.
Don't allow yourself to get "talked into" spending your hard-earned giga$$$ on stuff that you don't have independent verification of the value of. Thread Starter
Junior Member
Joined: Mar 2011
Posts: 11
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From: Colorado
Car: 84 trans am
Engine: 305ci. (lg4)
Transmission: t5
Axle/Gears: stock 10 bolt.
Re: Emissions in Colorado
I knew exactly what I wanted out of this, I'm not stupid. In case you didn't read the original thread, the whole point of this post was to ask questions about how to get around emissions, I would like to drive my car on the road with open headers just like all these hot rods I mentioned. That's the advice I'm looking for, I'm well aware of how I could get the car to pass emissions but I'm not willing to waste any more time or money messing with that. So again does anyone have any real advice pertaining to the subject I posted originally? I don't need any more smart *** remarks regarding experience for money spent.
Thread Starter
Junior Member
Joined: Mar 2011
Posts: 11
Likes: 0
From: Colorado
Car: 84 trans am
Engine: 305ci. (lg4)
Transmission: t5
Axle/Gears: stock 10 bolt.
Re: Emissions in Colorado
And just to clarify for anyone else who would like to make some smart-*** remark, I'm not seeking sympathy, I'm seeking advice. Has anyone on here successfully registered their vehicle in an emissions exempt County or state? And if so how did you do it, can you help me?
Joined: Sep 2005
Posts: 27,918
Likes: 2,448
Car: Yes
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Transmission: Sometimes
Axle/Gears: Behind me somewhere
Re: Emissions in Colorado
Has anyone on here successfully registered their vehicle in an emissions exempt County or state?
Or fix your car RIGHT instead of complaining about how you screwed up and coming looking for sympathy. Which is, put an exhaust system on it, and all the other things that your jurisdiction requires to be there, and that you could have known you were going to have to have BEFORE you porked the pooch.
And learn the lesson of (a) not letting someone "talk you into" doing something that involves A SHIPLOAD of cash BEFORE you know whether it will actually work; and (b) RESEARCH whether whatever it is you want to do, is LEGAL; again, BEFORE doing it. The most critical part: BEFORE.
And if so how did you do it, can you help me?
Joined: Sep 1999
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From: NJ
Car: 92 Firebird
Engine: 4.8 LR4
Transmission: T56
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Joined: Dec 2004
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From: Mile High Country !!!
Car: 1967 Camaro, 91 z28
Engine: Lb9
Transmission: M20
Axle/Gears: J65 pbr on stock posi 10bolt
Re: Emissions in Colorado
this thread should have been locked from the start.Can’t believe your asking for help to avoid emissions testing.
Junior Member




Joined: Oct 2017
Posts: 69
Likes: 5
From: Davis County, Utah
Car: 2021 LT1
Engine: Lt1
Transmission: Tr6060
Axle/Gears: 3.73
Re: Emissions in Colorado
The bigger question here is, why would you WANT to drive around in a car with open headers all the time? Regardless of whether you have ear protection or not
Joined: Sep 2005
Posts: 27,918
Likes: 2,448
Car: Yes
Engine: Usually
Transmission: Sometimes
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Re: Emissions in Colorado
Can’t believe your asking for help to avoid emissions testing.
Thread Starter
Junior Member
Joined: Mar 2011
Posts: 11
Likes: 0
From: Colorado
Car: 84 trans am
Engine: 305ci. (lg4)
Transmission: t5
Axle/Gears: stock 10 bolt.
Re: Emissions in Colorado
clearly people are unable to answer my question without being a dick. Nobody said I was breaking the law, clearly I am seeking a legal solution to my question. If it is legal to register the car in another state, why can't I do so? apparently nobody on here has done this.... I'll try some other forms where people are more helpful
Joined: Feb 2001
Posts: 13,758
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From: Cincinnati, OH
Car: '90 RS
Engine: 377 LSX
Transmission: Magnum T56
Re: Emissions in Colorado
You may not be breaking the law and I understand you are looking for help. However, it gives the impression that you are skirting the law. To points made above I think we should let this one die.
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