# Hollowing out a catalytic converter



## dfor (Dec 23, 1999)

With the way my truck is running I think the catalytic converter is becoming plugged. I need to bring it to midas or someplace to have it checked. If it is the cat;

Are there many mechanics that are willing to hollow it out? 
How long does it take?
Or am I better off just getting a new one. (boy are they expensive) 

My state doesn't require emisions to be tested on any truck over 8500 gvrw. 

Thanks for any suggestions.


----------



## wyldman (Jan 18, 2001)

Convertors are pretty cheap now,especially the universal ones.You can put a test pipe in place of the convertor to road test the vehicle to see if performance improves.If it does,then just replace it with a convertor.

Not many places will want to punch it out,unless it's for diagnosis only.You could do it yourself to test it.It will sound funny with the convertor punched out,as it acts as a resonance chamber.

You can buy a cheap universal convertor for less than $100.00


----------



## dfor (Dec 23, 1999)

Thanks wyldman. First I'll have it checked. Good to know that there are universal converters. I thought I'd have to go with stock, at $300-400.


----------



## CARDOCTOR (Nov 29, 2002)

fine for tampering with emission equipment

$25000.00 OR 6MONTHS in jail with a very lonely hair man







cardoctor


----------



## Mike 97 SS (Aug 11, 2002)

From what I understand, what the inside of the converter is made of, you arent supposed to breathe that crap in. So whoever does the punch out on it, should be wearing some sort of dustmask on his face. If you say they dont test emmissions where you are located, then I guess you can legally punch it out and drive it around. Around here, god help ya if you get caught punching out someones converter or running a straight pipe in place of a converter on any vehicle that is supposed to have a converter on it. What kind of vehicle are we talking about here anyway? Year, make, model, and motor size. Mike


----------



## Plow Dak (Jan 14, 2003)

Hey Chris
I can only find uni-cats for around 180 bucks. If you have a source i'd like to find out. I need a set for my sons car. Dual exhaust and mods. You know the routine

Mike


----------



## dfor (Dec 23, 1999)

It's a 1998 GMC K-2500 5.7 350. IF it is the cat, I'll just get a universal one. Sounds like a better way to go than punching it out. Thanks for leading me down the right path.


----------



## wyldman (Jan 18, 2001)

dfor - you will have to switch to the older stle y-pipe,as yours has an integral convertor.Take a look under it and you'll see what I mean.

There was another thread in this discussion forum on how to diagnose the convertor,and the part numbers for the older y-pipe retrofit.


----------



## wyldman (Jan 18, 2001)

Plow Dak - most all of our suppliers carry universal cats around here for $70-100.00,and that's Canadian funds,so I would assume they would be cheaper in the US.Maybe try a web search,and see what all you come up with.

If you don't find anything,I'll gladly ship you 2 from here.


----------



## Mike 97 SS (Aug 11, 2002)

How many miles on your truck? Kind of hard to see that a 1998 truck would need a converter already. Is your check engine light on? My truck is a 1992 with over 100k miles and the converter is still original. I bet I would feel an increase in power though if it was chopped out, its probably partially/mostly clogged with that many miles and considering the age also. Mike


----------



## CARDOCTOR (Nov 29, 2002)

my 98 dodge 3/4 v8 cat is bad

rattle all the time in gear

im under warranty
8-80,000



typical chrysler product



cazrdoctor


----------



## wyldman (Jan 18, 2001)

> _Originally posted by Mike 97 SS _
> *How many miles on your truck? Kind of hard to see that a 1998 truck would need a converter already. Is your check engine light on? My truck is a 1992 with over 100k miles and the converter is still original. I bet I would feel an increase in power though if it was chopped out, its probably partially/mostly clogged with that many miles and considering the age also. Mike *


Mike - you probably have the older style pellet convertor,which never plug up.The exhaust gases only pass over the beads,or pellets in the convertor bed,and not through them,so there is no,or very little restriction.


----------



## wyldman (Jan 18, 2001)

> _Originally posted by Plow Dak _
> *Hey Chris
> I can only find uni-cats for around 180 bucks. If you have a source i'd like to find out. I need a set for my sons car. Dual exhaust and mods. You know the routine
> 
> Mike *


JC Whitney has them for 89.95.Not a bad price.Made by Catco,they are good quality too.I have used many,and no problem.All cats have a mandatory 5 year emission warranty.

JC Whitney universal cats


----------



## ratlover (May 5, 2003)

You sure you dont have 2 cats? I think its true duals with 2 cats into a muffler with a single out of the muffler.

Good luck finding a shop to woller out one. Dont have any friends with welders to gut it for you? bit far from me otherwise I'd offer to hack on it 

I think that emmision stuff is supposed to be warantied for 100k....is it? Check the owners manual.....it might still be in waranty.

Why do you think its the cat? check engin light on? most of the time it will throw a code since the rear 02 sensors will pick up the failure. And btw on 02 sensors.....gutting the cat will probably **** off the rear ones and cause it to turn on the service engin soon light. its no biggy though....the sensors after the cats are just there to make sure the cat is ok, it will probably throw a code if you dont put o2 simulators in there but it wont hurt anything.


----------



## dfor (Dec 23, 1999)

The truck just turned 101,000 miles. The engine runs and idles fine. But when I give it any more than about 25% of the pedal, the truck just boggs down. Been doing this for about 3 months now, and seems to be getting worse. About 600 miles ago (2 weeks) I put in 1/2 bottle of Chevron Techron to about 34 gallons of gas. Last friday the truck started to run pretty darn good. Took right off. Thats when the check engine light comes on (when it starts running good). Code 131 & 151. Both 02 sensors before the cat. Drove it Sunday and it wasn't so good. Today it was so so. I can't figure it out. I'll have Midas check the cat and go from there. 

ps- just climed under there and it looks like I have 2 cats. wyldman, I guess thats why you say I'll need a y-pipe.


----------



## Mike 97 SS (Aug 11, 2002)

Wyldman, the converter on my truck looks like the big flat kind, like a pancake sort of. Is this the kind you are talking about also? Dfor, I bet Wyldman can tell you what those codes mean when he gets here, hang loose.  Mike


----------



## wyldman (Jan 18, 2001)

Not sure in the US,but most emission stuff is 5 yr/50000,with 8 yr/80000 on the computer.Cats are usually 5/50K.

It could also be a fuel pump going bad.It may just pay to have someone check it out top to bottom before you shell out for a cat,or cats.


----------



## wyldman (Jan 18, 2001)

> _Originally posted by Mike 97 SS _
> *Wyldman, the converter on my truck looks like the big flat kind, like a pancake sort of. Is this the kind you are talking about also? Dfor, I bet Wyldman can tell you what those codes mean when he gets here, hang loose.  Mike *


You do have the pellet style convertor Mike.They didn't go to the honeycomb style until 94 or so.

I tried looking up those codes,but no jive.He should have an OBD-II system,so the trouble codes would be like P0131,or P0151,but they are not valid codes.Maybe he can update us on the codes.


----------



## dfor (Dec 23, 1999)

I had an Autozone check the codes. 
Haynes manual says;

PO131 O2/HO2 sensor signal voltage low
PO151 HO2S circuit low voltage Bank 2, sensor 1


----------



## Plow Dak (Jan 14, 2003)

Thanks wyldman 
Definately the info I needed. Never even thought about J.C.
Mike


----------



## wyldman (Jan 18, 2001)

No problem Mike.I'm sure if you shop around (even the web),you'd find them even cheaper.


----------



## ratlover (May 5, 2003)

Its probably time to change the o2 sensors any way....they are kinda pricey though. . when was the fuel filter changed? How bout the rest of the tue up? at 100k its pretty much time to do a once over on the newer motors.


----------



## johngus (Aug 14, 2001)

Being that your truck is a 1998.It is OBD2 emissions.If you hollow out the cat you will get a check engine light on as there is o2 sensors on both sides of the cat to monitor if its working.I would look into the o2 codes first and do a fuel pressure test.You can also hook up a vacuum guage on the motor to check for a clogged cat.low vacuum will indicate a clog.also checkfor flow at the tailpipe.


----------



## johngus (Aug 14, 2001)

when replacing o2 sensors,buy the AC Delco ones,they're a little more money but will work best.


----------



## wyldman (Jan 18, 2001)

Your right on the OEM sensors.Most of the aftermarket stuff isn't worth a crap.Some of the Bosch stuff is good,but I've still had problem on certain application due to slight design differences.


----------



## dfor (Dec 23, 1999)

Well, I'm finally able to bring the truck to the dealer. My apointment is tomorrow. BUT, its running ok this afternoon. It wasn't earlier in the day. I'll probably bring it in. Can they still determine what is wrong if its running ok? What I didn't mention before is that when rev it up, it pops and coughs (sounds like its coming from the intake). Could it be carbon at the EGR valve? Thanks a bunch for all the responses.


----------



## johngus (Aug 14, 2001)

If the check engine light was on there will be a code logged in the ECM of what the fault was.If theres no faults logged and it's running properly you'll have a tough time finding it.You say it was coughing and sputtering.Was this on a rainy or damp day?If it was I'd be looking at the ignition wires,cap and rotor.I doubt the EGR valve being carboned up would cause the problems you describe but an easy test for it is to remove it and push in on the pintle to see if it sticks open.good luck at the dealer and hopefully they'll find your problem


----------



## dfor (Dec 23, 1999)

UPDATE,

Wyldman you were right when you said it could be the fuel pump. That was it. Runs great now. Thanks everyone for all the replys.


----------



## Mike 97 SS (Aug 11, 2002)

Glad to hear you got it fixed. Did they replace the whole sending unit and all or just the pump and screen? And did they use genuine OEM parts? Mike


----------



## dfor (Dec 23, 1999)

OEM parts. The whole sending unit. (looks like part # 25314319) Dealer installed it.


----------



## Mike 97 SS (Aug 11, 2002)

Cool, best way to go, OEM parts whenever possible. Mike


----------



## wyldman (Jan 18, 2001)

Good choice on the OEM stuff.We have had nothing but trouble with any aftermarket pumps on the newer GM trucks.


----------

