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Catalytic Question 1983 K5 w/small block

Sqeejo

Sqeejo

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I am looking at putting true dual exhaust on my 1983 K5 Blazer. Question is do I need to put cats on the exhaust? The last owner had straight header pipes going into straight pipes, however I want to get legal. Since I don't have anything to reference I wanted to see what kind of setup everyone is running with their duals.:D
 
I'm pretty sure it's a federal law and not a state law but if you run duals you must go through a single cat then you can go out with dual pipes. You cannot run a true dual exhaust even if you put a cat in each pipe. You'd be best to check with your local smog shop to see what they'll look for.
 
Don't take this wrong plenty of people disagree. Federal law does not allow you to modify the number or location of the catalyst. Which basically means if it was originally equipped with a single cat you are limited to one.
 
YGBSM!

I know you guys didn't write the law, but isn't the objective to reduce pollution. A dual exhaust with dual catalytic converters should improve mileage. What a concept!!!

No offense guys, but I'm sure glad I don't live in an area that requires emissions inspections.
 
As stupid as it is the law is a Federal law so even if your locality (like my whole state) doesn't require that sort of check it's still a Federal Law that you can be ticketed for. Just ask my buddy and his loud as fuzuk 86 longbed with dual Flowmaster 40's...
 
84zz4ss said:
Don't take this wrong plenty of people disagree. Federal law does not allow you to modify the number or location of the catalyst. Which basically means if it was originally equipped with a single cat you are limited to one.
Click to expand...

You are also basing this on the inspector's knowledge of the specific application.

I am running a 79 that had ALL emission stuff removed by the PO. I replaced the entire exhaust and emission stuff. I am running dual exhaust/dual cat. Three years of inspections in AZ with no problems.

Just went last week for smog. I failed the visual b/c I knocked a vacuum tube off when I was doing the AC build. Smog was fine. Put the vacuum hose back on, drove back into line and passed visual and smog.
 
Sqeejo said:
I am looking at putting true dual exhaust on my 1983 K5 Blazer. Question is do I need to put cats on the exhaust? The last owner had straight header pipes going into straight pipes, however I want to get legal. Since I don't have anything to reference I wanted to see what kind of setup everyone is running with their duals.:D
Click to expand...

I live in a sniffer county (Collin) and have had true duals on my 89 for about 13 yrs. I run ceramic Flowtechs into HiFlo cats into Magnaflows exiting in the stock location only at an angle to the corners to baloney tips. No crossover because I like the dual sound and there is really not a benefit (per 4wd magazine test). My O2 is in the drivers side collector. No issues with the bone stock engine, and no issues with the 270hp roller.

I just put new cats on it for $403. In my case, the Cats Must be in place. I have never been questioned about having 2 cats.
 
Once again, I don't want to offend anyone. But the state of Montana is a "Big Picture" state when it comes to motor vehicle registration. Compare your state (especially The Peoples Republic of Kalifornia) with Montana:

a.) No sales tax
b.) No inspections
c.) No emissions inspections
d.) Vehicles 11 years old and older can get a permanent registration. That's right it never expires as long as you own it. And it only costs roughly three times the annual fee.
 
Sounds pretty good to me...but catalytic converters are still a Federally mandated thing.
 
You should also keep in mind, that with the number of cat thefts going on right now, removing a cat even in Utah is risky. A shop can be fined $10k for removing a cat, and most of them are going to recycle, so it could bite the shop.

I had always been told that if the cat wasn't there when you bought the vehicle, then they couldn't make you put one back on. Granted, I heard this from shops and not from the law. I do know that modifying any emission system on any vehicle made after 1989, can result in some pretty hefty fines, but doesn't seem to be as big a concern with prior years.

***This is not legal advise, nor do I condone the removal of emissions systems.***
 
it all depends on where you live, when i did my exhaust in oklahoma, the shop ran true duals from the headers thru 2 40 series flows, and then out behind the rear tires. no cats no question. oklahoma doesent require emissions testing, and when i moved to colorado either did weld county. but if i went to the next county over they would test but also it depends on what kind of test. i have heard of sniffer test where as long as your within a certain level for the age of the truck they will let you pass. also if you fail three times they have to pass you because by law they cant force you to spend money to fix the emissions (not sure if thats true but thats what i heard) in a emissions county here in colorado (back in the mid 90's) my parents 90 sub passed emissions with true duals and flows with no cats. so just check with your county
 
State law cannot override Federal law. Just because the state chooses not to nail for it, or to test for emissions, doesn't make it legal to do. I think that is the point that most people are trying to make, Federal law says you cannot modify emissions systems on vehicles equipped with them.

I will say however that it is pretty unlikely that a US Marshall is going to stop you on the freeway and check your cats. Unlikely doesn't mean impossible.

Edit: It is no different from having a state that issues two license plates, but you don't mount one. It isn't a state law, it is a Federal law that says you must display them both if your state issues them. That is why you are not supposed to be allowed onto a Federal installation without the proper plates. I know my Dad had to add a front plate hanger to his custom bumper in order to drive his truck to work.

***Not intended as legal advise, nor do I condone the removal of emissions equipment***
 
I understand what you're saying with regard to Federal laws superseding state late laws and how it applies to emissions.

In re-reading my post I can see how it could be taken that I am advocating removal of emissions equipment. I'm not. I just don't see how installing two catalytic converters (when their used to be one) to make a true dual exhaust system is such an horrific act.

New Hampshire license plates say "Live Free Or Die" on them (I'm not sure if they still do.).

Being a transplanted Vermonter, I subscribe to that philosophy and resent the he** out of the oversight of Big Brother and the loss of personal freedom in this country.
 
The problem is that catalytic converters are pretty specific in their "ideal" operating range.

Changing the amount of exhaust flowing through them/heat by either changing their location from the engine, or changing the quantity, can affect their operation.

Stupid to prevent you from doing the "right" thing? Yes. Reason behind it? Yes. Single 3" is a better idea all the way around anyways.
 
YUp as far as i know it's illegal to run anything after 81 (not specifically sure on that one) without cats on them.

I say this cause my mom has an 81 Trans am and they won't pass it legally round here unless you know people in which i do.

I say go with the duals to one cat into dual mufflers and out the back or sides and then you won't have anymore problems ;)

Seems any other way is just gonna cause trouble
 
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