high flow precats?
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From: Rio Vista ca.
high flow precats?
What I'd really like to do is replace the precats with a Y pipe from Mid America and install a high flow main cat into my existing Corsa cat back exhaust. Since I live in the Peoples Republic of California that is not an option, even though I should still be able to pass the emissions test, just not the visual. Does anyone make a high flow pre cat system that I could legally install with a high flow main cat and bolt the whole thing up to my Corsa system? I have an '89 coupe.
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From: Summerland B.C. Canada
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From: Rio Vista ca.
Thanks for the link, Agent 86. Are those precats legal in Ca. and will they have to be welded on by a muffler shop? The installation info on the site is not working.
Thanks, Kim
P.S. The other option is to go with no precats as stated in my preferences in my post and switch between stock and high flow system every two years. How much of a hassle would this be? Installing the Corsa cat back wasn't too bad. If changing back the front part of the exhaust system wasn't much worse then it would be a doable option.
Thanks, Kim
P.S. The other option is to go with no precats as stated in my preferences in my post and switch between stock and high flow system every two years. How much of a hassle would this be? Installing the Corsa cat back wasn't too bad. If changing back the front part of the exhaust system wasn't much worse then it would be a doable option.
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From: Phila., PA burbs
Melting Slicks
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From: backwoods upstate ny
imho, IF the nuts that hold the head pipes to the manifolds have been "off" in the last couple of years, changing the front pipes/cat as a unit is much easier than the rear (cat-back)...the front assy is more compact and weighs less than the rear.
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From: ceres ca
St. Jude Donor '08
On my 87 I took out the front Y and drilled a couple of holes in the top of the precats. Then used a steel rod and hammer to bust up the material inside. Dumped out the material, welded up the holes and reinstalled the pipe. You can't see it because the holes are on the top.
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From: SE NY
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Since you live in KA one solution to max air flow might be to install those hi-flow pre-cats into a mandre-bent 2 1/2" front Y and have the main cat gutted with a 3" pipe welded inside.
They you should pass both visual & tester emissions plus your flow potential would be increased to >800cfm, good to nearly 400chp.
They you should pass both visual & tester emissions plus your flow potential would be increased to >800cfm, good to nearly 400chp.
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From: Near Lockport NY Black 1986 Coupe
Are you just trying to pass visual? If so, you can gut out the pre-cats and the main cat yourself, just make sure you put a pipe inside the main so the air doesn't recirculate and resonate. I'm having that problem right now but soon to be fixed.
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From: Rio Vista ca.
I need to pass both visual and emissions. I was thinking a high flow main cat and no precats (won't pass visual but should pass emissions) or maybe gutted pre cats and high flow main cat (should pass both). Not sure if the precats with a gutted main cat would pass the sniffer test.
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From: SE NY
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The pre-cats were added as a supplement to the main cat due to cat limitations back in the day.
There are now small bullet-cats that could be used in the pre-cat position to take care of all emission needs.
But the main restrictions on the L98 exhaust are:
-the pre-cats
-the waffle-bent front Y
-the single main cat
A pair of hi-tech & hi-flow (>400cfm) bullet cata along with a test pipe inside the main cat should do the job for you as far as emissions. The only remaining restriction would then be the waffle stock front Y pipe.
There are now small bullet-cats that could be used in the pre-cat position to take care of all emission needs.
But the main restrictions on the L98 exhaust are:
-the pre-cats
-the waffle-bent front Y
-the single main cat
A pair of hi-tech & hi-flow (>400cfm) bullet cata along with a test pipe inside the main cat should do the job for you as far as emissions. The only remaining restriction would then be the waffle stock front Y pipe.
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From: Rio Vista ca.
Thanks for the clarification, 65Z01. It's starting to look a lot like the best way to beat this ridiculous restriction on appearance is to swap out a new Y pipe and high flow cat with my stock exhaust once every 2 years. How hard can it be? Once I free up the existing 20 year old bolts on the existing Y I should be able to unbolt everything from my Corsa cat back and be good to go, right? Any suggestions or tips on how to make this process easier will be greatly appreciated. Thanks to everyone who replied to my questions. 
Kim
Kim
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From: SE NY
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How hard can it be? Once I free up the existing 20 year old bolts on the existing Y I should be able to unbolt everything from my Corsa cat back and be good to go, right?
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From: Rio Vista ca.
About 8yrs ago I dropped my OEM front Y to get the headers out and port them. I soaked the lower flange bolts overnight with PB Blaster and all the retainer nuts came lose with no problem. Coating with a moly lube before assembly should hold for 2yrs. Not sure about how much difficulty there would be in getting off the main cat??
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From: Rio Vista ca.
[QUOTE=89Corvette6spdFX3;1566025459]I have a Magnaflow "High Flow Cat" that is to be welded in place of your pre cat. I only have one so you'd need to order another but here's a pic if you're interested.
I'm kind of looking for something I can just bolt up like the cat-less Y pipe from Mid America. I don't weld and none of the muffler shops in this town would touch my exhaust since there's probably nothing wrong with the OEM stuff that's on the car now. I'm still leaning toward switching out a new Y pipe and high flow cat (bolt on) for my stock exhaust every 2 years in order to pass smog here in Ca.
I'm kind of looking for something I can just bolt up like the cat-less Y pipe from Mid America. I don't weld and none of the muffler shops in this town would touch my exhaust since there's probably nothing wrong with the OEM stuff that's on the car now. I'm still leaning toward switching out a new Y pipe and high flow cat (bolt on) for my stock exhaust every 2 years in order to pass smog here in Ca.
