Recommendation for cats - ZR-1 Net Registry Forums

GTOger · 07-09-2013

I still have 2 years before I can run "classic" plates here in Texas, so in the meantime, I'm subject to emissions testing. The car has failed with high Nox and HC. The kicker is I got a letter from the state that tells me they won't issue new tags because the car has not passed emissions. How it makes any sense at all that our Governor will issue exemptions for coal-fired power plants, but my 39k mile Corvette is apparently at fault for killing the environment is beyond me but that's another rant for another day.

What I really want to ask is: What recommendations are out there for replacement cats for a 1990 ZR-1?

A26B · 07-09-2013

The problem for the 90~92, is that the cats are welded to the exhaust manifolds, like a collector section, so they will have to stay on the manifold. New cats can be added downstream but first, the old cats should be cleaned out/gutted completely, which requires removing the manifolds. Here's a photo to see how it is made.

The foregoing is the least expensive. The other solutions would include buying another set of used manifolds with good cats, 90~92 or 93~95 which are listed in the parts manual as direct replacements. The other option is to toss the stock manifolds and install long tube headers & flange/clamp in cats behind them.

if you go with aftermarket cats, use only those with metallic substrate.

Kevin · 07-09-2013

i've had good luck with russian blues and orange tabbies...

wait wrong cats

Fully Vetted · 07-09-2013

Quote:

Originally Posted by GTOger

I still have 2 years before I can run "classic" plates here in Texas, so in the meantime, I'm subject to emissions testing. The car has failed with high Nox and HC. The kicker is I got a letter from the state that tells me they won't issue new tags because the car has not passed emissions. How it makes any sense at all that our Governor will issue exemptions for coal-fired power plants, but my 39k mile Corvette is apparently at fault for killing the environment is beyond me but that's another rant for another day.

What I really want to ask is: What recommendations are out there for replacement cats for a 1990 ZR-1?

When I bought my car last year I couldn't even get the title transferred until it would pass. It came from a non-sniff state so it needed some work. It already had SW long tubes on it and no cats. So, I took it to Corey and he retuned it and I gave him the cheapest bullet cats I could find at Summit Racing and he installed them using the good flange connectors. I replaced the oxygen sensors and it passed. I don't know by how much it passed but it passed. Then I promptly removed the cats...

GOLDCYLON · 07-09-2013

My advise if you need to get another 2 years try to find a set of used replacements. Trust me this is a PITA and a lot of work however for my 91 I went with a set of long tubes and randam tech hi flow cats. The car still will not pass the treadmill test. It might on a sniffer test only and I dont know what your emissions tests are like in Texas.

Fully Vetted · 07-09-2013

Good recommendation. Random Tech are the best you can buy. They're a little pricey but no doubt the best. If I was going to leave them on I would have gone with them but I only needed "testers" so I went cheap.

GTOger · 07-09-2013

There is something to be said for the removable method. You know, so you can pull the cats off for off-road use. It may be time to do the header thing. The manifolds have to come off the car either way, so.... yeah, it may be time.

USAFPILOT · 07-09-2013

The cheap bullet cats that came with my SW headers are causing me a headache. I can just barely pass by running 1/3 tank of 93 Oct and a quart of denatured alcohol from Home Depot. The Nox will come down when you put in the alcohol but the HC's will increase. It is all about the blend.

GTOger · 07-09-2013

Thanks for that, Pilot. I'd ideally like to have cats that can bolt-in/out. I wonder if there are any recommendations?

Jagdpanzer · 07-09-2013

Here are the temporary cats I rigged up to get through Virginia emission test.
Link to full details http://www.zr1.net/forum/showpost.ph...57&postcount=5

07-09-2013	#1
GTOger Join Date: Nov 2010 Location: Dallas, TX Posts: 198	Recommendation for cats I still have 2 years before I can run "classic" plates here in Texas, so in the meantime, I'm subject to emissions testing. The car has failed with high Nox and HC. The kicker is I got a letter from the state that tells me they won't issue new tags because the car has not passed emissions. How it makes any sense at all that our Governor will issue exemptions for coal-fired power plants, but my 39k mile Corvette is apparently at fault for killing the environment is beyond me but that's another rant for another day. What I really want to ask is: What recommendations are out there for replacement cats for a 1990 ZR-1? __________________ [B]1990 Corvette ZR-1 (#1930) Red/Black, Stock Engine, Henderson Performance custom ECM, FIC Injectors, B&B exhaust, Kenwood DNX6160[/B] Other Rides: 1992 Pontiac Firehawk (#010), 1967 Pontiac GTO 1998 Porsche 968, 2000 Harley Davidson FXST 1986 Pontiac Trans Am, 1931 Ford Model A Tudor Deluxe

07-09-2013	#2
A26B Join Date: Dec 2003 Location: Arcadia,OK Posts: 3,394	Re: Recommendation for cats The problem for the 90~92, is that the cats are welded to the exhaust manifolds, like a collector section, so they will have to stay on the manifold. New cats can be added downstream but first, the old cats should be cleaned out/gutted completely, which requires removing the manifolds. Here's a photo to see how it is made. The foregoing is the least expensive. The other solutions would include buying another set of used manifolds with good cats, 90~92 or 93~95 which are listed in the parts manual as direct replacements. The other option is to toss the stock manifolds and install long tube headers & flange/clamp in cats behind them. if you go with aftermarket cats, use only those with metallic substrate. __________________ Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 *ZR-1, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed. Last edited by A26B; 07-09-2013 at 12:50 PM.*

07-09-2013	#3
Kevin Join Date: Jun 2005 Location: pittsburgh Posts: 4,632	Re: Recommendation for cats i've had good luck with russian blues and orange tabbies... wait wrong cats __________________ It's not the car, it's the people - Doug Johnson 90 r/r "KEYS ON" nick named "T.L.B"

07-09-2013	#5
GOLDCYLON Join Date: May 2007 Location: Peoria, AZ Posts: 9,155	Re: Recommendation for cats My advise if you need to get another 2 years try to find a set of used replacements. Trust me this is a PITA and a lot of work however for my 91 I went with a set of long tubes and randam tech hi flow cats. The car still will not pass the treadmill test. It might on a sniffer test only and I dont know what your emissions tests are like in Texas. __________________ GOLDCYLON - 91 ZR-1 #2014 GOLDCYLON - 90 ZR-1 #2794, 4L60e (Formerly Schrade's) GOLDCYLON - 11 CTS-V Arizona State Director 91 WHITE/BLACK #2014. 380 P&P&PCed,Ported Heads, Jeal Long tubes, Corsa Exhaust/FIKSE FM-5s /LED TLs, LED Headlights, Front Wilwood 6 piston narrowlite calipers and rear Wilwood caliper street shop mod,CNCed Coolant Pipes,TPI Cvr,Filter cover,Stainless Bolts, DRM/DOM PROM /ZFDOC mod build #102,DRLs,BMAD with stainless Debris Screen,Coplan Air Blaster, Pioneer APP Radio 4,Brey-Krause HB,Sub Bar,Fire extinguisher seat mount,DRM Coilovers,LEDs everywhere,Compass mirror (orange),V1 DIC hidden display, Homelink sun visor, Carbon Fiber top x3 and APSIS Carbon Fiber interior, APSIS CF Steering Wheel/NAPA Leather, Banski trailing arms, Guldstrand front suspension,urethane bushings from Prothane (total suspension) ZFDoc drive shaft safety loop, raptor shift light (orange),AO engineering louver front plate, Console seat cushion, 96CE seats with black custom Sheepskins, ss billet catch can,Viper remote entry/alarm,Cragar Rear Louvers,LED side louver lights, Dewitts Radiator with SPAL fans and a Woods 160 T-Stat 90 RED/BLACK #2794. 4L60e Automatic Stage V by RPM Transmission, TCI Dedicated TCM, OBX Stainless Headers, Corsa Exhaust, SAN Secondaries and Haibeck PROM, Exotic Muscle Coil overs, LED Interior Lights, LED Tail Lights, LED Headlights, 94 Sport seats with black custom Sheepskins , Cragar rear louvers, GS Front calipers, Banski Trailing arms, APSIS Carbon Fiber steering wheel, Front and Rear Baer Eradispeeds, DRLs, Guldstrand front suspension,urethane bushings from Prothane (total suspension), Dewitt's Raditor with Dual SPAL fans and a Haibeck 170 T-Stat 11 RED/GREY CTS-V

07-09-2013	#6
Fully Vetted Join Date: Sep 2012 Location: Rockwall, Tx Posts: 1,510	Re: Recommendation for cats Good recommendation. Random Tech are the best you can buy. They're a little pricey but no doubt the best. If I was going to leave them on I would have gone with them but I only needed "testers" so I went cheap. __________________ _________________ 1994 AB/Grey #141 430 RWHP/392 RWTQ FBI Lyposuction / Secondaries relieved of duty / SW Long Tube Headers / Corsa Exhaust / FIC SS Injectors / MSD Coils / Lightweight Pulleys / Corey tuned B & M Shifter / Aluminum Flywheel / Samco Hoses / Shelby Series One's / C4 No Flex Frame Stiffener BBC - Bling By Carter: Custom ZR-1 Center Caps / Custom Plenum Plate / Air Box Knobs / TB Cover / Oil Filter Cover

07-09-2013	#7
GTOger Join Date: Nov 2010 Location: Dallas, TX Posts: 198	Re: Recommendation for cats There is something to be said for the removable method. You know, so you can pull the cats off for off-road use. It may be time to do the header thing. The manifolds have to come off the car either way, so.... yeah, it may be time. __________________ [B]1990 Corvette ZR-1 (#1930) Red/Black, Stock Engine, Henderson Performance custom ECM, FIC Injectors, B&B exhaust, Kenwood DNX6160[/B] Other Rides: 1992 Pontiac Firehawk (#010), 1967 Pontiac GTO 1998 Porsche 968, 2000 Harley Davidson FXST 1986 Pontiac Trans Am, 1931 Ford Model A Tudor Deluxe

07-09-2013	#8
USAFPILOT Join Date: Aug 2007 Location: Spring TX Posts: 1,348	Re: Recommendation for cats The cheap bullet cats that came with my SW headers are causing me a headache. I can just barely pass by running 1/3 tank of 93 Oct and a quart of denatured alcohol from Home Depot. The Nox will come down when you put in the alcohol but the HC's will increase. It is all about the blend. __________________ 1994 #293 ZR-1 Stainless Works Long Tube Headers, B&B catback w/ X-Pipe, 18" Shelby Series One Wheels, SLP CAI.

07-09-2013	#9
GTOger Join Date: Nov 2010 Location: Dallas, TX Posts: 198	Re: Recommendation for cats Thanks for that, Pilot. I'd ideally like to have cats that can bolt-in/out. I wonder if there are any recommendations? __________________ [B]1990 Corvette ZR-1 (#1930) Red/Black, Stock Engine, Henderson Performance custom ECM, FIC Injectors, B&B exhaust, Kenwood DNX6160[/B] Other Rides: 1992 Pontiac Firehawk (#010), 1967 Pontiac GTO 1998 Porsche 968, 2000 Harley Davidson FXST 1986 Pontiac Trans Am, 1931 Ford Model A Tudor Deluxe

07-09-2013	#10
Jagdpanzer Join Date: Apr 2007 Location: Northern VA Posts: 2,661	Re: Recommendation for cats Here are the temporary cats I rigged up to get through Virginia emission test. Link to full details http://www.zr1.net/forum/showpost.ph...57&postcount=5 __________________ Phil Wasinger 1994 Torch Red ZR-1 WAZOO Member George Braml Intake

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