Is it OK to remove Cat system?

Howdy Guys, I have a '91 B2200 with a 4 banger and 5 speed, carb model (No A/C). I have never owned a vehicle with a Catalytic Convertor on it and I know that when they get clogged up they are expensive to replace. I would like to remove it but ONLY if it will not harm anything.

I don't know anything about all the smog crap on vehicles as I have always owned older trucks and jeeps (pre'72) so my worry is that with all the smog stuff is the Cat really needed? If I remove it will it screw the engine up at all? I know that some engines are designed to have a certain amount of back pressure so I'm wondering if that is the case with a Cat system on these little trucks.

The muffler is disconnected now and was that way when I bought it last month but if I can remove the Cat without doing any harm I will put a new thrush turbo muffler on. Also I would like to get more than 23mpg (it has a cab high alum camper shell) I'm getting on the freeway now so if I install headers and a electric fan do you think that will give me another 5mpg?
Much Obliged
Patrick
Skagit County, Wa

First question: do you have emissions testing in your area? If so you can't remove your e-system because you won't pass testing.

Second: everything can be removed (OEM Carb, O2 sensor, passenger side fender wiring harness, pair tubes, vacuum lines etc) if you do a weber and pacesetter header swap.

Third: Header and e-fan won't give you 5 mpg. Adjusting your driving habits will give you better results - short-shift, lift-off early, don't over-rev... etc.

Nowhere in the United States is it legal to remove any emissions equipment, but that doesn't stop people from doing it.
No harm will come to your engine by removing the cat. If your county requires emissions testing, you better get a new one. You'll fail without it.
As far as mileage, it seems to be a toss up with these trucks. Some guys claim positive results, while others don't notice much difference... if any.

THANKS Guys.....I am in a county that has No emissions testing so I will just remove the Cat if it goes bad,

What would be the advantage if I did the things you said....

>> everything can be removed (OEM Carb, O2 sensor, passenger side fender wiring harness, pair tubes, vacuum lines etc) if you do a weber and pacesetter header swap.<<

and what exactly are "Pair Tubes"

Much Obliged
Patrick
Skagit County, Wa

In my opinion not much - I wasn't advocating the swaps, simply pointing out you can do it. I made those mods and didn't get a single MPG improvement - I even went back to the OEM cooling setup. The OEM emissions "system" is pretty good at squeezing out the best possible MPG from that setup and you get the benefit of passing emissions, usually very easily.

Unless you suspect a problem with your CATs I wouldn't worry about them. The primary almost never clogs and the secondary is "only" $100-$129. Give it a tune up and save yourself a bunch of time and money keeping it OEM for as long as you can.

Dan

If I understood your original post, you are getting 23mpg on the highway now...with your large/tall camper top? That doesn't sound too bad. If it's taller than your cab, then that is certainly causing you some more drag and MPG, aside from the extra weight you are carrying around.

If you aren't having any major issues with the OEM setup, then I would stick with that and just go over it to make sure it's parts are functioning as they should be... EGR valve & Reed Valves are clean, all of the vacuum line are good, solenoids working properly, ect. If you have an especially clean truck and you pull the cat and/or other emissions components, it might work great for you without emissions testing, but if and when you decide to sell it, you may be limiting your market if the emissions parts aren't even there. You could end up jumping through a lot of hoops chasing 1 or 2 mpg. If all of the factory components are working good, it will do a good job of maximizing the fuel economy. The system is rather "smart" compared to a Weber which doesn't even use an O2 sensor. If it was causing you a lot of grief and you couldn't get it running right and/or you needed a carb overhaul, that's when I would make the switch to Weber and maybe go with a header.

As for the eFan, I put one on my truck, but did it mostly for extra AC condenser cooling in city traffic because I was switching from R12 to 134a. I didn't do it for engine cooling or to gain any fuel efficiency. It sounds like your primary concern is your highway mileage. Even in city traffic, the engine load caused by your factory fan is very small. So when you're on the highway, the fan load on the engine is practically nil. I wouldn't expect any measurable efficiency gain on the highway.

Tune it, but if it ain't broke, don't fix it!

Thanks Scotch....I will look at my Clymer manual so see how to clean EGR and Reed Valves. Rebuilt motor only has 60k on it. I will take your advice and keep it stock. The only issue I have is the choke doesn't work I think cuz it wont idle and engine dies (if I don't keep it revved up) until it warms up (about 2 miles) other than that is runs like a raped ape on the freeway but the power is not very good on these little trucks. My brothers 3 cylinder 5 speed GEO METRO could probably kick my butt in drag race...LOL

I really Appreciate the help
Patrick
Skagit County, Wa

Actually you can pass an emissions test without the CAT. The machine cannot tell whether it's there or not and the exhaust will pass without it.

Used to do exhaust work and gut cats. They still passed the machine.

But it does have to be there. Federal law states you must have all emissions equipment that came with the vehicle. Even ones considered antique. Whether they check for it or not depends on if they are supposed to.

If you have to replace one or both just get a high flow aftermarket cat and let it do it's job at cleaning the exhaust gasses.