yabadaba

Guys, I have a stock 2001 Z28 that will be having a GMMG catback fitted soon, but I've just found out that my driver side cat needs replacing so I'm going to replace both sides with better flowing cats.

People on here seem to recommend the Magnaflow 59959 (3"), but that seems to be with headers installed. Would it be the 59956 (2.5") that I would need given that the GMMG is 2.5" and I'm running with the stock manifolds (also 2.5" I think)?

RevGTO

iTrader: (12)

GM extended the warranty on f-body cats ... I think it's good to 120k, IIRC. Call your dealer and see if you can get it replaced for free. The Magnaflow cats you're looking at are not meant to fit in the stock location.

yabadaba

Yeah, I'd heard that, but I'm in the UK so I guess that warranty won't apply, even though they sold Camaro's over here from 98 to 02.

RevGTO

iTrader: (12)

I don't see why not ... are GM's warranties invalid overseas? Were the Euro spec cars equipped with the same cats as US cars? Have you talked to a dealer over there?

yabadaba

Err...to confuse things a little more, my Z28 was a Japanese export version that was imported here from Tokyo a few months ago! Still, I guess the cat warranty might still apply. I'll call GM (Vauxhall over here) tomorrow.

If not, then I guess it's either stock cats, or direct-fit replacements by Eastern Catalytic or the Magnaflow Direct-Fit cats. The direct-fit Magnaflows are about twice the price of the 59959's though, but if that's what I'm going to need then so be it.

Badguy7

iTrader: (6)

Yeaa, just try and get direct fit replacements from GM or any replacement cat. Ive got those Magnaflow SPUN 3" cats on my car w/ stock header's. The guy could not remove the stock cats, so he just gutted those out and then added some pipe and then welded the new cats right after that. I didnt know this at the time, if i did. I probably wouldve just waited till i got my LongTubes.

You'll basically be riding around with 4 cats on, 2 gutted and 2 working properly. It doesnt throw a code or anything, seems to run just fine. Its upto you, but it would be awhole lot better just getting replacements for the stock cats.

RevGTO

iTrader: (12)

The other thing you could to is some fabbing to connect some straight pipe to the manifold, and then weld in a Magnaflow universal fit cat. 2.25" is the factory pipe size. Search Magnaflow's site for the appropriate "Carsound" cat. Doing this would probably be much cheaper than going direct fit - if you have a good exhaust shop that will work with you.

yabadaba

Okay, thanks for that info guys. I'll speak to my mechanic this week and see if he will be able to work with the universal cats. Or maybe I should just try and run with the stock cats for a few more months until I can afford to ship over some long tube headers.....very tempting...

Formulated

iTrader: (16)

I've got the 59956 cats in an off road Bassani y-pipe with the Bassani mid headers. They're nice because they're so small, and fitment isn't an issue. If you don't mind spending a bit more money, get an offroad y-pipe for the stock cats and weld the Magnaflow cats in place. I think you would be pretty happy with that setup. You could go the distance for headers as well.

Badguy7

iTrader: (6)

I forgot to mention that 1 of my stock cats was broken at the time too. I rode around with it for a couple months, does nothing really bad other then mess with your gas mileage.