Pre-Cat gutting

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Oct 30, 2001 | 11:25 AM

Plasticman

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Race Director

Joined: Nov 2000

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From: Beverly Hills (Pine Ridge) Florida

Pre-Cat gutting

Has anyone ever figured out a way to gut the pre-cats on the early C-4's?

Like to keep the stock look (with the cat housings), but free up the exhaust a little.

Thanks,
Plasticman

Oct 30, 2001 | 11:58 AM

Flame Red

Le Mans Master

Joined: May 1999

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From: Windermere FL

Re: Pre-Cat gutting (Plasticman)

Plasticman,

I have heard people have opened up the pre-cats, gutted them and welded them back shut. That's fine if you have access to welders.

Otherwise you can get a new front Y-Pipe from places like MAD that solve the problem.

Oct 30, 2001 | 01:13 PM

Larrym96815

Safety Car

Joined: Oct 1999

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From: Honolulu HI

Re: Pre-Cat gutting (Flame Red)

It is easy to get the front Y pipe off or it was on mine. I have often wondered if any household chemicals would dissolve the "guts" in the pre cat. Maybe muratic acid (swimming pool stuff) or paint stripper or drano or ?????? Any one with an old cat laying around that wants to experiment. You could then just pour the chemical through, rinse it out and put back together with no visible signs of altering. Any chemist out there?

Larry

Oct 30, 2001 | 01:14 PM

65Z01

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Joined: Dec 2000

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From: SE NY

Cruise-In II Veteran

Re: Pre-Cat gutting (Plasticman)

It seems like there are two options:
-cut em off, gut em and weld them back
-cut them open, gut em and weld them back together

I chose to have a custom 2 1/2" front Y fabricated for the extra flow. Random Tech makes a 3-stage cat that is 49-states legal with pre-cats removed.

Oct 30, 2001 | 06:15 PM

Plasticman

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From: Beverly Hills (Pine Ridge) Florida

Re: Pre-Cat gutting (65Z01)

I do have a spare set, so I think I will experiment. Opening them up and then welding them back will work (as long as the alignment is maintained, and I have a spare block and headers that can do that).

As for chemicals, I think anything that attacks the cat material will also attack the tubes themselves (at least that is the risk).

I am also thinking about taking a heavy punch, and shaking it up and down in the Y pipe, and see if I can get any chunks of cat out.

Thanks,
Plasticman

Oct 30, 2001 | 07:36 PM

AS84

Melting Slicks

Joined: Aug 2000

Posts: 2,009

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From: Springfield MO

Re: Pre-Cat gutting (Plasticman)

On another car, I took of the H pipe (in this case) and used a die grinder with a cut off wheel to cut open the top half ot the cats. I made three cuts as long as I could with out interfering with the main body of it and then folded the piece I cut back. I then removed the stuffing and folded the piece back down. Welded it back "shut" and was back installing the H pipe in now time flat. Havn't done the vette yet, but it is on my to-do list!

Oct 30, 2001 | 09:40 PM

DON M

Drifting

Joined: Dec 2000

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From: Sarasota FL

Re: Pre-Cat gutting (Plasticman)

Ecklers carries a Walker/Dynomax 2 1/4" Y-pipe w/o precats and a matching main coverter. (I'm sure you could do better on price, but you can check them out in their catalog). They carry a CARB exemption number, and are 50 state legal. I would do that before I would fool around with trying to gut the stock ones and end up with a punch bent 2 1/4" stock pipe.
Here in VA they don't check very carefully and my set up passes visual and IM-240. (see sig)
Don