I have a bad bank 2 catalyst on my 08 Alpha and was wondering if anyone has tried any of the universal ones like Magna-Flo or any others as a replacement vs the high priced direct fits.
Thanks

 

Your converter is plugged or is it the 02 sensor?

 

Bad converter

 

Anyone with any help about this?

 

A Cat is a Cat. If it was me, I would replace both secondary Cats at the same time with a MagnaFlow high flowing cat over an exhaust shop shelf model every time. I would also make the exhaust true dual while at it, but that is just me.

If you are going to do the work yourself, go the direct fit route. The basic difference is welding vs no welding bolt in with most brands. Look under the Alpha, the exhaust is flattened and shaped for fit.

The direct fits tend to bolt to the exhaust manifold flange and end where they bolt to the exhaust back flange. Universals are the Cat itself, cut out the old, weld in the new, or buy them with the correct size clamp on slide over ends.

I have not tried them with an H3, but have with many prior GM trucks.

 

I removed the secondary cats and used MF high flows in place of the primary. I can smell fuel at startup and the cats let out alot of noise.
If you are looking for stock quiet use the MF stock replacement and keep all four
If you want a 1500 series truck sound remove the secondaries (Ive read that they only have primary cats)

 

The Cats are at the exhaust manifold and I do want to replace both.
I already run a true duel exhaust but just not sure if the aftermarket cats were going to work.
The factory 1 is almost $1000 and 4-6 weeks to get, so not a good deal at all.
Thanks guys for your help and reply's too.

 

Only the I5s have a cat in the exhaust manifold. The stock Alpha has 4 Cats, one pup cat in each side of the Y Pipe immediately AFTER the exhaust manifold collector flange, then 2 more larger Cats down stream in each side of the pipe before the Y flange and clamp. The rears are not monitored, the front 2 are.

The Cat pipe diagram.

So you could change one, but to get to it you will have to drop the entire side of that Y pipe, after disconnecting the Y and rear exhaust, so you might as well do both on that side. In fact, this is probably the biggest PITA GM truck exhaust there is to work on.

#6 & 9 come together to form the connecting Y. The driver side is flattened near the clamp joint making it an additional challenge.


How many miles are on your truck?

 

I paid a visit to MagnaFlow and they do not even have a direct fit Cat for the Alpha yet, says under development. They do have replacement Cats themselves, and you would have to cut out the old and replace with new. Did not spend enough time to see if they clamp on or weld in.

 

Thanks Doc.
The one I was looking at there appears to be some sort of universal one if I was looking at the right one.
Really appreciate the help and effort too.