I'm going to need new exhaust here soon. If I remove the catalist will this help performance? I don't think my state checks for this anyways.
CK5
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catalist removal
- Thread starter wazzabie
- Start date
no performance gains, just dirtier exhaust
it's also illegal to remove, regardless if they check
it's also illegal to remove, regardless if they check
ya dontget busted removing one. . . . 
if you got a stock pancake cat then at least swap it for a honey comb cat for a lot more flow.
those pancake cats realy choked the flow.
if you got a stock pancake cat then at least swap it for a honey comb cat for a lot more flow.
those pancake cats realy choked the flow.
I don't care about the law end of it.
If yours is restricted, removing it will help.
If it's a Carbed engine, there is no benefit to keeping it except the possibility of cleaner exhaust if everything is tuned properly.
If it's a FI engine it will run better if a CAT is in place unless you reprogram for no CAT.
A better free flowing CAT would definitely help if you want to keep a CAT
I just pulled my cat out and put straight pipe back to a 2 chamber muffler. 350 tbi and it is a night and day difference. way more power. I dont have any idea about the chip programing
But it runs awesome now so I may look into it to make it even better
But it runs awesome now so I may look into it to make it even better
4xcrazy
3/4 ton status
I don't have Cats on my 350TBI either, had to drop the stock exhaust due to significant damage on the last offroad trip I went on. running headers and dual pipes with mufflers only. Drives fine, no computer issues related to lack of Cats.
The only real engines that need the Cats or reprogramming without them are the ones running after Cat 02 sensors, and all those are for are to make sure the Cat is working properly. I just went through that crap with my dads car, the factory Cat had burnt out and was throwing the SES light. that after cat sensor is set for a specific temp setting after the gasses are worked over in the Cat. Replaced the burnt out (hollowed out) Cat with a new "used" one and everything worked fine and passed the plug & play emissions testing here in Phoenix..
Right now the truck is in Inidiana, where they don't do any sort of emissions testing or any type of vehicle inspections, so in reality, no one would really know about it's lack of converters.
The only real engines that need the Cats or reprogramming without them are the ones running after Cat 02 sensors, and all those are for are to make sure the Cat is working properly. I just went through that crap with my dads car, the factory Cat had burnt out and was throwing the SES light. that after cat sensor is set for a specific temp setting after the gasses are worked over in the Cat. Replaced the burnt out (hollowed out) Cat with a new "used" one and everything worked fine and passed the plug & play emissions testing here in Phoenix..
Right now the truck is in Inidiana, where they don't do any sort of emissions testing or any type of vehicle inspections, so in reality, no one would really know about it's lack of converters.
Confedneck
3/4 ton status
Shady, that's only true for OBD1 and if his vehicle had after cat sensors, which it doesn't. He should not run into any performance issues by doing this. It's also a $10k federal fine if a shop is caught removing them, not sure on a personal violation. You can always hollow it out, or cut off the heat shields and weld them back over the pipe to pass visual.
DizturbedOne
1/2 ton status
If it is not clogged in anyway, you won't notice any difference removing it unless you have one of those really old flat ones. Then just swap it out for a newer one.
If it IS clogged and you do not plan on replacing it, I would not recommend removing it. Hollowing out the catalyst in the converter with a prybar or the like would be a much better option to keep you out of any trouble.
These smog laws will only get stricter in populated areas as time passes, believe me. Don't bother with the possible headache of removal when you can just hollow it out and pass visual with no affect of your flow at all anyways and no worry of adverse performance issues due to a clogged catalytic converter.
It will only affect your computer if you have what is known as a "downstream" O2 sensor (after the catalytic converter). None of these trucks had them to my knowledge (I've never seen an OBDII square body GM truck in my life). If you have a newer motor swapped in (OBDII was mandated in 96, most stuff had it by 94/95 and quite a few vehicles had it as early as 92) you may have it.
If it IS clogged and you do not plan on replacing it, I would not recommend removing it. Hollowing out the catalyst in the converter with a prybar or the like would be a much better option to keep you out of any trouble.
These smog laws will only get stricter in populated areas as time passes, believe me. Don't bother with the possible headache of removal when you can just hollow it out and pass visual with no affect of your flow at all anyways and no worry of adverse performance issues due to a clogged catalytic converter.
It will only affect your computer if you have what is known as a "downstream" O2 sensor (after the catalytic converter). None of these trucks had them to my knowledge (I've never seen an OBDII square body GM truck in my life). If you have a newer motor swapped in (OBDII was mandated in 96, most stuff had it by 94/95 and quite a few vehicles had it as early as 92) you may have it.
The shops around here (no smog laws or emmision tests) will do full duals with out cats as long as it comes in with open headers or manifolds and no exhaust at all. They are just not allowed to remove them themselves with out putting one back on.
My K5 is a 78. Back in the 80's dual exhaust was added to it. I'm looking at the exhaust... it may not have the cat curently. The two tail pipes go back to the mufflers. The two pipes do not connect. Would the k5 have both a muffler and cat?
Cut that Biatch off and call it a day, one sawzall and 5 seconds and a new piece of pipe to go in its place, a few clamps and your good to go. Done it tons of times, normally makes the exhaust sound better too. 
When I was out west, I played the game and made my trucks legal. Now I live in N.E. Wisconsin where there is no inspection what so ever of any kind. None of my vehicles have cats on them any more except my 1999 C1500 Silverado. (because it only has 60,000 original miles and is in mint cond.)
79rustyk10
3/4 ton status
As far as fuel injection systems go... TBI is about as dumb as they get, the system barely knows what its doing, let alone anything past the O2 sensor.
Cut the thing out and be done if thats what you want. I ran TBI with no cat for YEARS with no problems pertaining to lack of the cat. In fact, within the next few months I will be removing the cats on my ford f-150 DD as well. (removong cats and better Y pipe is supposed to net a 2-3 mpg increase with improved drivability on the 86-96 ford trucks)
However if theres an O2 sensor past the cat, like all modern EFI systems you gotta keep it.
(I wasnt bashing TBI its a great system for what it is and the time it was produced, just very, very, primitive)
Cut the thing out and be done if thats what you want. I ran TBI with no cat for YEARS with no problems pertaining to lack of the cat. In fact, within the next few months I will be removing the cats on my ford f-150 DD as well. (removong cats and better Y pipe is supposed to net a 2-3 mpg increase with improved drivability on the 86-96 ford trucks)
However if theres an O2 sensor past the cat, like all modern EFI systems you gotta keep it.
(I wasnt bashing TBI its a great system for what it is and the time it was produced, just very, very, primitive)
