I heard the cats will plug up if you remove the smog pump. If so, how long does it take for that to happen? Thanks guys.

 

Well, as soon as i ditched the emissions, a hole burnt thru the AIR piping to the converter (still unsure how that happened) and the converter clogged up real quick. I'm still shocked at how fast everything occured, of course, my converter was probably over 50% clogged due to aging in the first place.

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--Steve S--
1984 Trans Am 305 LG4, 5 speed
Daily Driver, Flowmaster 80 Series
NOW FEATURING: Holley 600 cfm & vacuum advance

 

Crap. And I have dual cats too so that will double suck. Thanks for the heads-up man.

 

What the AIR does is inject air into the exhaust to complete combustion. When the exhaust leaves your heads and enters the headers, some of it is still unburned, so the Air Injection Reaction system injects air into the exhaust to burn the rest of the charge before it enters the cat. Air is also injected into the cat to further burn anything that may remain before it exits your tailpipes into Mother Nature. Also, the AIR tuben that enters the cat, aides in the reaction that occurs inside the converter. If you remove there components, unburned fuel will enter your catalytic converter and thus clog it very quickly.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 Hot Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

7.5" 10 Bolt with 3.42s soon to come!

 

cant the ecm and o2 combo keep the output clean enough to not need additional air?

it does maintain a 14.7:1 most of the time. Shouldn't the exhuast be clean enough

 

all the o2 does is moniter the oxygen levels. it send a certain ammount of volts to the ECM to compinsate, but i doubt that the ecm will be able to compinsate that much. and if it can, youll feel the horsepower drain. id say either rip out the cats, or put the pump back on. if you take of the cats you may, and i reitterate, may, gain horse power. im not to familiar with 3rd gen Fs but usually car come from the factory with too much back pressure. you take the cat off and you gain ponies because the engine can breath better. however you may get a decrease in power if you have to little back pressure. freew flows are a good alternate too.

my advice: Headers to dumps. no pesky piping to worry about, your neighbors will love it, especially when you leave to go to work at 5:30am, and every cop you go by will give you a thumbs up.

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1985 WS6 Trans AM
T-tops
bone stock sloth of an engine LG4
T-5 tranny. thank god, i couldnt stand an LG4 auto.
Plans for an LT-1 or LT-4,
dual flowmaster exaust,
& a pounding stereo.
mods right now include a radar detector.

 

I wouldn't have pulled the thing but the pump was seized and cost over $100 to replace. I guess now I'm looking at a $400 repercussion of that though . What cats can I get without AIR hookups that bolt into a dual-cat '90 IROC L98? Don't wanna let someone in there with a torch anytime soon. I found some online for like $380 that bolt right in but they had AIR hookups so I figure they require it or they will plug as well. Thanks guys.

 

You'll have to get someone to cut the old ones out anyway. Either with a torch or a sawzall.. lol You'll need a new Y-pipe if you want to go to single cat also.

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92 Z28 5.7
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Ported stock heads, XR270HR-10 cam, TES headers
Crane AFPR, Flowmaster catback, MSD ignition
#24 SVO injectors, 1LE aluminum driveshaft.

Best ET 13.3@107 mph

Click here to see my car at Truspeed.org
Check out Truspeed
Check out the Bin Archive

 

Do you have a sniffer test or just the visual inspection? If you have a sniffer, you're stuck with the problem of buying new catalytic converters.

However, if you have a visual inspection you can pull the cats out and gut them, it will make the exhaust note a little louder, but you can probably get away with it when they inspect you. This would be the cheapest option since it costs next to nothing (unless the piping wont come off!)

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--Steve S--
1984 Trans Am 305 LG4, 5 speed
Daily Driver, Flowmaster 80 Series
NOW FEATURING: Holley 600 cfm & vacuum advance

 

I'd like to stay with the dual cat setup, and you can purchase the whole assembly that bolts up to the manifolds and the cat-back with AIR hookups, but I can't find it without them. I don't have emissions inspections here, but I'm not sure how I could go about gutting the cats without cutting them out of the system. I guess I could cut them out with my sawzall, gut them and cram a pipe in them, and then clamp or get them welded back in. I thought I would just replace them in case we eventually do have inspections here, but if you guys have ideas I'd be all ears. Thanks for the help.

 

My 81 Z had the air line to the cat. disconnected when I bought it. Ran that way for a year till I blew the plug out of when I missed 2nd gear at about 55 mph one day. My 86 IROC had the smog pump belt off it when I bought it and the owner told me he'd only put the belt on for inspection day, then removed it when he got home. My son's 83Z (5.0 HO) had the air tube to the cat. burned in two at the rear of the head when we bought it 2.5 years ago. No cat problems on either 3rd gen so far. We'll wait and see before we spend money to fix what might not be "broke".

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Z's r Best

 

I was thinking I will get an exhaust backpressure gauge ($30) and test it before I do anything, but it's good to know that not all cats clog up without the AIR.