Hollowing out a cat converter?

[UOFLcards]

I would take the cat off and gut it. I did this when my 86 cutlass had the 307 and single exhaust, i hollowed it out with a crow bar and made sure all the pieces where out before reinstallation.It was a little louder with my cherrybomb glasspack that replaced the muffler also.

That is also what I have. Single exhaust with a cherrbomb glasspack. Mine is a 305.

 

[moose]

it is best to weld in a pipe so the air flow is not disturbed by changes in diameter. if you use a long chisel, you have loose material, and an irregular path for airflow--this creates turbulence and lowers power.

Damn, once again I stand corrected by the laws of physics... :lol:

 

[BulldawgMusclecars]

Around here, they pay good money for convertors at the scrapyard :wink:

Here too...for a while there was a rash of convertor thefts from trucks and SUVS in parking lots here in Atlanta. Just 2 quick cuts with a cordless Sawzall.

I have gutted them as a temporary fix, but it would be best to either force a pipe through the center and put it back, or go with a high flow cat. Or, if you can do it yourself or can talk someone else into it, weld in a straight pipe.

 

[axisg]

2 schools of thought when hollowing out a convertor

A: remove the unit from the car, then hollow it out with the method of your choice ( hammer, screwdriver, prybar, whatever you have ) then reinstall ( I like using hi-temp copper silicone to seal it back up with new bolts as you will break the old ones getting the cat off ).

B: remove the exhaust from the back of the cat and pull it aside. With the car safely on stands, wheels blocked and running at appx 2000 rpms ( turn up your idle screw ) take a chisel or prybar and break it up from behind. This method will soon have all the chunks get pretty hot and they will fly back out as you loosen them up ( actually pretty funny to watch as you will get very dirty and probably burned at some point). You then reinstall the exhaust with a little hi-temp silicone and new bolts.

Without welding in a tube to the now empty cat it makes a resonance chamber and the exhaust will be a little louder. I have been running a hollowed cat in my car for 3-4 years now and it''s fine without the pipe welded in.

The older cats and newer aftermarket hi-flow units are made up of ceramic material and not valuable. Unlike the cats on newer cars which contain platinum.

Your exhaust will flow better if your cat was clogged but it will stink of unburnt fuel when the car is not moving in traffic.
Breaking up the ceramic is like beating a brick in a metal box into chunks small enough to fit out the hole. Not impossible but time consuming

 

[RITTER]

Like "megaladon6" said ... the correct way to gutting the cat is to cut the thing in half. Grind everything out of it and weld it back together. It would be much better if you can stick a straight peice in the cat, so its a true "straight-thru" cat. If you just shove a tube through the cat and don't get everything out, it will eventually starting rattling and you'll have to do it again :idea:

 

[pontiacgp]

why??...like it was posted you can sell the cat and buy a universal free flow that are not expensive and there is very little restriction. I have 2 magnaflow SS spun cats that were originally developed for race cars where the tree huggers got their way the restriction is almost nothing...

 

[UOFLcards]

I'll more than likely just either take the cat off and put a straight pipe in it's place or go with a high flow cat.

 

[UOFLcards]

I can back up the claim on increase in noise. I went from a stock muffler to a flowmaster 80 series and the sound didn't change at all until I took the cat off. Now yes, it did make a world of difference as far as sound, but not performance. Nothing you can notice anyway. Instead of "gutting it" I would suggest eliminating it or finding a high flow cat if a converter is required in your area.

Any suggestions on a high flow cat?

We do not have inspections in my area but it is illegal to remove the cat here and I was told if I want to put the "old timers" tags on it then I might have to have it inspected. No sure on that though.

 

[UOFLcards]

I'm going to be cutting my cat out this weekend and replacing it with a straight pipe. What size straight pipe will I need to replace the cat?

 

[Likethat]

About 15 years ago I watched a show in my garage on how to high flow a stock cat with a 2in spade bit on a 3 foot long bit extension and a drill. With repeated starts of the car to see the flow gain. All with the tail pipe unbolted from the back of the cat and the bit entering thru that end. Great TV show The host looked fermilure.