[Product Review] MagnaFlow Direct Fit Catalytic Converters for C5 Corvette ZO6

Don’t Buy This Part.

It’s not too often that I get a product which is flat just a bad design, but that’s the case with this MagnaFlow direct fit catalytic converter assembly (PN 448988) for C5 ZO6s.

For the last couple of months, when driving our 2004 ZO6 LeMans Edition, I’d been getting a regular MIL for DTC P0430 which is a fault with Bank 2 cat efficiency. With HPTuners’ VCM Scanner app running on my Panasonic ToughBook, I could easily see that the Bank 2 Sensor2 signal was starting to mimic the Bank 2 Sensor 1 signal. When I swapped the sensors side-to-side, problem showed up in the Bank 1 Sensor 2 signal. That pretty much decided the issue–the Bank 2 cat was bad, so I began looking at new cats.

The replacement factory cat set for an ‘04 ZO6 is obscenely expensive, so I considered aftermarket cats. Since this car is licensed in the People’s Demokratik Republik of Kalifornia, I was restricted to aftermarket cats with California Air Resources Board (CARB) Executive Order (EO) approval. I first looked at MagnaFlow because it’s a California manufacturer of cats and I figured they’d do best with CARB-legal cats. Boy was I wrong.

I ordered the MagnaFlow 448988 cat set from Summit Racing Equipment. As I’m close to Summit’s Sparks, NV warehouse, it arrived a day later–I love Summit!

I got “3 Balls 39”, our C5 ZO6 up on jack stands and pulled off the old cats and the CORSA X-Pipe I had on the car. I opened the MagnaFlow box and right away was a little uneasy. There were no installation instructions–not really an issue with me, personally, because I knew what to do but, for someone who’s not an experienced Corvette DIY, no instructions might be a problem. I, also, noted that the top copy of the California-required cat warranty was missing. Hopefully, I won’t have any warranty issue, I thought.

I lifted the MagnaFlow direct-fit cat set into place, supported it with a jack stand, slid the manifold flange rings in place, then installed the exhaust manifold flange nuts and bolted the cats’ center support to the pad under the rear of the clutch housing. Right away, the installation didn’t look right. I crawled out from under the car and looked at the side view. The two cats were hanging down 3-inches lower than did the stock cats. “WTF?” I wondered.

Let me digress…I didn’t select the MagnaFlow part only because it was made in CA. I emailed MagnaFlow’s media rep, Richard Waitas, and asked for some information about the part. Turns out Waitas is a C5 ZO6 owner and assured me that ground clearance would not change in a practical sense and that 12 years of cat technology advances and MagnaFlow’s mandrel-bent pipes could improve performance.

So, back to looking at the system hanging down 3-inches at the cats and 2 ½ inches at the cat’s rear connection. Ground clearance? Not.

I should add that this MagnaFlow cat set is actually not a direct fit because, if you put it on a car with a stock exhaust, you’ll have to cut the last couple feet of the stock exhaust off and weld or clamp it to the rear of the MagnaFlow cats because they’re about two feet short and lack the bolt together muffler connections. Since I had previously cut off the rear of the stock cats and replaced that with the CORSA X-pipe rear section, I’d be ok. Well…except for the fact that the rear connection was 2 ½-inches lower.

If this had been a quarter or half an inch low, I’d would have just gotten out my hydraulic jack and a block of wood and “bent” the system a little to get it up higher, but I wasn’t going to be able to fix such a huge misfit, so I removed MagnaFlow’s so-called “direct fit” set of cats.

I emailed Summit Racing’s customer service folks, explained the problem and sent them an image. They not only took the part back after I’d had it a month, but they emailed me a prepaid, UPS return label and promised the part would not go back in stock, but be returned to MagnaFlow. Summit Racing Equipment has great customer relations and is my favorite sources for aftermarket performance parts. Visit the Summit web site.

There are other direct fit CARB-legal sets of cats for C5 Z’s on the market but I decided to try two of Flowmaster’s universal CARB legal cats and have a local exhaust shop weld them in place of the factory cats, so for now and until I can get the Flowmaster cats, I put the factory cats and CORSA X-pipe pack on the car.

Bottom line: If you own a C5 ZO6 registered in California and you’re thinking about buying the Magnaflow 448988 Direct Fit catalytic converter assembly, DON’T DO IT. The part will not fit.