My 2001 has an intermittent rattling noise on acceleration. Tapping on the cats with a rubber mallet emits a rattling noise which would appear to indicate replacement is needed. I see several complete Cat Conv/H pipe as After Market replacements available. 2 from A/P, 3 from CATCO and 1 from Eastern. Does anyone have any experience or info on the quality/fitment of any these parts? I would prefer to find a nice low mile OEM take off but they seem to be fewer out there as the years go by.

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AP Exhaust 645856 - AP Exhaust Direct-Fit Catalytic Converters

Catalytic Converter - Direct Fit
Part Number: APH-645856

AP Exhaust 645868 - AP Exhaust Direct-Fit Catalytic Converters

Catalytic Converter - Direct Fit
Part Number: APH-645868

Catco Catalytic Converters 9187 - Catco Direct-Fit Catalytic Converters

Catalytic Converter, Direct-Fit, Stainless Steel, Each

Part Number: CTO-9187

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Catco Catalytic Converters 9203 - Catco Direct-Fit Catalytic Converters

Catalytic Converter, Stainless Steel, Chevy, 5.7L, Each

Part Number: CTO-9203

 

I’m in same boat as you. No input other than magnaflow has an option as well

 

Two sets of Magnaflows didn't fit my "98 so they were returned.

 

Have you considered upgrading to an x-pipe with high flow cats?

 

^. This. It opens up more options for you.

 

I had a CARB Magnaflow midpipe installed for a while. Did the job just fine, but be careful with aftermarket units if you're lowered at all. The OEM pipes are designed to snug up to the body and leave the undercarriage flat...aftermarket options may hang lower and make some nasty noises when you try to enter/exit driveways.

 

Do a little research on high flow cats and check engine lights. Just make an informed decision whichever way you go.

 

Thanks. Looks like I’ll be going this route

 

Thanks for the input and comments.
I'm not really looking for performance gains, just returning to stock type function. Having cats with increased thickness and hanging lower than the stock would be undesirable.
The images shown of the compete aftermarket systems are not real clear but the cats themselves appear to be wider and thicker than the factory units.
Can the existing cats be cut out and replacement cats be welded in?
If so, what cats would be well suited to return to original clearances and function without triggering any emission codes?

 

I'm glad you posted this thread, gtzy. I'm in a similar boat as you and I had not ran across these options. I'm in the military and stationed in Germany and have a C5Z over here. With the inspection it goes through to register it, I'm also interested to hear if these are true bolt on replacements for the factory h-pipe//cats.

 

I have a good take off that I removed when installing long tubes and high flow cats. I'm in the Sarasota area of Florida. I'm sure shipping would be highly prohibitive though.

 

All I can offer is my impression that magniflow has good customer service. My used car had a broken trim bracket on a magniflow axle back system and the factory sales rep offered to exchange the entire set up for new. I was in contact with the guy trying to find the best shop to weld my bracket without the weld rusting over time.

 

The Catco exhaust for 1999 does not have the pup cats like the 00-04's, the cats are 4" thick the pipe is 2.5" diameter so you only have 3/4" of the cat below the pipe. I have a set waiting to go on as my left side cat is showing signs of being plugged.

 

I'm pretty sure an exhaust shop could cut out the bad cat and weld in a new one?

 

I did the American Headers high flow cats and x pipe. Stainless and attached right to the stock axle back. Nice quality 3 inch piping.

 

You'd think, but then you must've never tried to have this done. I did, and learned the hard way that there are three problems we face with obtaining suitable replacement cats - one, the stock converters are low-profile, rectangular and nearly flat to the pipe height. Two, they have no heat shields. Three, the pipe inlet is offset from the outlet by a good inch and a half. See the following photo of mine after I removed it.



GM has discontinued these. There are few if any good options left to maintain proper ground clearance and fit within the center tunnel. Catco and AP Exhaust both used to list similar parts, but are now both owned by the same parent company and are no longer producing them ("obsolete" was their term for it). My C5 is highly modified and supercharged, makes more power than any human should rightly be allowed to possess, and my state no longer has emissions testing at all. But not only do I NOT want to be the guy with the Corvette with the stinky exhaust polluting the environment and everyone around me, it is a convertible and I can assure you that NO female passenger wants to inhale toxic exhaust fumes at every stop sign or stoplight with the top down on a nice sunny summer's day any more than I do. Not having cats is simply not an option, and I've been trying to find the 645856 upgrade with the California pup cats for months with no success.

 

Best bet is to buy stock used setup. I know most people want an arm and a leg for them, but not everyone. Helps that you don't NEED the pup cat model and I can't think of a logical reason to seek one out since it's more weight, slight reduction in power, two more cats to clog/deteriorate, and no more efficient than the later 2 cat setup.

If you're not lowered a lot, you'd be fine with a not-so-snug fitting aftermarket setup as well. Although with the blower setup, most tuners/shops would highly recommend ditching the cats if you don't absolutely need them. I understand the desire to want to run them though, no judgment there.