90 ZR Cat Converters

[Belsy]

My cat on rite side must have broken loose inside (sounds like motor is coming apart) scared me real good!!

Rattling sound tells me they have to come off and be dealt with. Any input on replacements, new styles, or just removal or gutting would be appreciated. Could be time for headers if there are any out there? If I went to headers should I keep cats? What is the popular opinion?

[Z Factor]

Originally Posted by gene

My cat on rite side must have broken loose inside (sounds like motor is coming apart) scared me real good!!

Rattling sound tells me they have to come off and be dealt with. Any input on replacements, new styles, or just removal or gutting would be appreciated. Could be time for headers if there are any out there? If I went to headers should I keep cats? What is the popular opinion?

Well Gene it depends on what you are looking to do. First make sure it is the cat. If so chances are you can find another set of manifolds/cats without to much trouble, and I might be able to help in that regard. If you want to keep it stock that is fine, but if you put on headers with a catback system (with or without cats) you will see a noticeable HP gain that you can feel and hear.

Since you live in Florida you don't have to worry about inspections so you could also gut your cats to save money if that is your main goal. However most will recommend you go with headers and exhaust. An X-pipe in place of the resonator will be even better, but it will also be very loud so you need to determine if that is for you. My set up is headers with no cats into an x-pipe and a newer style B&B. Needless to say it is very loud but I enjoy the HP gains. If it was a daily driver I would tone it down because it is too loud for everyday driving for me.

[zr-1assassin]

ya... kill the cats if you can. gut them, cheap and eeeeffective! gives power and great sound. dont know if it will trip anything because thats where the o2 plugs in but it should be ok

[blackjack]

are the stock cats very restrictive ?? how much hp gain by just gutting them? worth the trouble ?? i already have borla exh,with the many restrictions removed,and no resonator(x-pipe)
blackjack
91/1735

[jonszr1]

I amnot positive but i think you would gain 10 rwhp . hope that helps

[Belsy]

Originally Posted by blackjack

are the stock cats very restrictive ?? how much hp gain by just gutting them? worth the trouble ?? i already have borla exh,with the many restrictions removed,and no resonator(x-pipe)
blackjack
91/1735

I cut a trap door on the bottom along the welds with a sawzall bent it away then gutted the cats!! Then folded 3 sided trap cut back into place and mig welded seam, ground down for smoothness then wrapped w/ exhaust wrap to keep heat in for o2 sensor and appearance.
Can say car runs better and as we all know less restriction can't hurt!!

[Z Factor]

Originally Posted by blackjack

are the stock cats very restrictive ?? how much hp gain by just gutting them? worth the trouble ?? i already have borla exh,with the many restrictions removed,and no resonator(x-pipe)
blackjack
91/1735

I'm not sure if anyone has done a dyno after just gutting the stock cats, but I suspect it will make a difference. The trouble with the stock system is not only the cats but the restrictive nature of the manifold design as well. So while gutting the cats will help a little, replacing everything with headers will make the greatest gains.

[blackjack]

i suspect my z will be louder,with the cats gutted,as i have no resonator and an x pipe..
bj

[Z Factor]

Originally Posted by blackjack

i suspect my z will be louder,with the cats gutted,as i have no resonator and an x pipe..
bj

Indeed, most cats reduce the exhaust note to one degree or another.

[blackjack]

thanks,z factor
bj