Cleaning cat
Thread Starter
Instructor
Joined: Aug 2014
Posts: 185
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Cleaning cat
Hey all, I have an 85 vette with an aftermarket exhaust that was put on approximately 10 years previous to me owning it. Should I be worried about all the Dust or any toxic chemicals inside it?
Team Owner
Joined: Jul 2004
Posts: 28,332
Likes: 3,247
From: Hartford WI
Team Owner
Joined: Dec 1999
Posts: 34,873
Likes: 487
From: Lacey WA RVN 68-69
NCM Sinkhole Donor
Unless there's a reason to think that the cat or any interior portion of the exhaust system is coming apart, there's no real reason to bother with it. Do you hear any sort of rattling from the exhaust when the engine is running?
Are there any indications of rust that have created pinholes or spots so weak that you can push on the pipe and move it? Condensation will form inside the exhaust and if the engine doesn't always run long enough, rust/corrosion can develop.
If you want to make a "test pipe", that's between you, your exhaust shop, and whatever emissions testing you have to have done.
Are there any indications of rust that have created pinholes or spots so weak that you can push on the pipe and move it? Condensation will form inside the exhaust and if the engine doesn't always run long enough, rust/corrosion can develop.
If you want to make a "test pipe", that's between you, your exhaust shop, and whatever emissions testing you have to have done.
Team Owner
Joined: Jul 2004
Posts: 28,332
Likes: 3,247
From: Hartford WI
Unless there's a reason to think that the cat or any interior portion of the exhaust system is coming apart, there's no real reason to bother with it. Do you hear any sort of rattling from the exhaust when the engine is running?
Are there any indications of rust that have created pinholes or spots so weak that you can push on the pipe and move it? Condensation will form inside the exhaust and if the engine doesn't always run long enough, rust/corrosion can develop.
If you want to make a "test pipe", that's between you, your exhaust shop, and whatever emissions testing you have to have done.
Are there any indications of rust that have created pinholes or spots so weak that you can push on the pipe and move it? Condensation will form inside the exhaust and if the engine doesn't always run long enough, rust/corrosion can develop.
If you want to make a "test pipe", that's between you, your exhaust shop, and whatever emissions testing you have to have done.
Thread Starter
Instructor
Joined: Aug 2014
Posts: 185
Likes: 0
Could you buy a test pipe? If not, take it out and blow air into it to get the dust off. And if a long steel rod should slip, make sure it does not hit any of the honeycombed part of the cat again and again or it will break it apart. If it does break apart, compressed air will blow out the dust.
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Thread Starter
Instructor
Joined: Aug 2014
Posts: 185
Likes: 0
Unless there's a reason to think that the cat or any interior portion of the exhaust system is coming apart, there's no real reason to bother with it. Do you hear any sort of rattling from the exhaust when the engine is running?
Are there any indications of rust that have created pinholes or spots so weak that you can push on the pipe and move it? Condensation will form inside the exhaust and if the engine doesn't always run long enough, rust/corrosion can develop.
If you want to make a "test pipe", that's between you, your exhaust shop, and whatever emissions testing you have to have done.
Are there any indications of rust that have created pinholes or spots so weak that you can push on the pipe and move it? Condensation will form inside the exhaust and if the engine doesn't always run long enough, rust/corrosion can develop.
If you want to make a "test pipe", that's between you, your exhaust shop, and whatever emissions testing you have to have done.
Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 411
From: WV
If you hear rattling then the cat is shot..The media inside has broken apart and will eventually clog the pipe, or at least restrict flow.....If you want or need to retain a cat, then get a Magnaflow cat, the one I got as a replacement is so free flowing you can hold it up to the sky ,look through it , and see birds flying by...The only thing in it is a couple screens, so there is almost zero restriction......WW
Last edited by WW7; Dec 23, 2014 at 10:33 PM.
Melting Slicks
Joined: Jun 1999
Posts: 2,931
Likes: 127
From: Ashland Alabama
Also if your doing this for some "performance" improvement and theres nothing really wrong with the cat... don't.
I gutted mine on my 86 and all it did was make it louder. Zero change in 0-60, 1/4 mile, top end, etc.
I gutted mine on my 86 and all it did was make it louder. Zero change in 0-60, 1/4 mile, top end, etc.
Melting Slicks
Joined: Jun 1999
Posts: 2,931
Likes: 127
From: Ashland Alabama
Smell goes away normally removing them.
On the first gen of cats it was a good idea to gut them as they were very restrictive but by the time the c4 came out the flow is actually very good with them. Agreed its better to keep the cats on.
Team Owner
Joined: Jul 2004
Posts: 28,332
Likes: 3,247
From: Hartford WI
Actually the "stinky" exhaust is with the cat Smell goes away normally removing them.
On the first gen of cats it was a good idea to gut them as they were very restrictive but by the time the c4 came out the flow is actually very good with them. Agreed its better to keep the cats on.
Smell goes away normally removing them. On the first gen of cats it was a good idea to gut them as they were very restrictive but by the time the c4 came out the flow is actually very good with them. Agreed its better to keep the cats on.
For me, I took them off and put them back on for noise control. Just gave it more noise and if the gain is insignificant, why should I put up with more noise?
Melting Slicks
Joined: Jan 2008
Posts: 2,054
Likes: 120
From: AZ
timely, as I am looking into adding a pair.
Agreed; also my experience.
As a federal offense, not mentioned in THIS thread, but many others, it is a very expensive fine, a blemish on the hobby, for little or no gain.
Perhaps, but not if if the system is functioning properly. Any smell is probably due to lack of AIR injection or a used up catalyst.
Perhaps, but not if if the system is functioning properly. Any smell is probably due to lack of AIR injection or a used up catalyst.
Last edited by whalepirot; Dec 24, 2014 at 10:20 AM.
Team Owner
Joined: Jul 2004
Posts: 28,332
Likes: 3,247
From: Hartford WI
I have Random Technologies cat and removed the AIR. Easier to work around the engine and the cat brings down the noise a lot. I'll put up with the noise IF it can generate enough power but not if it doesn't.
Le Mans Master
Joined: Mar 2004
Posts: 5,107
Likes: 171
From: Dublin CA
The rattling you hear at hard acceleration in your 85 is just due to the age of the car 
...not the cat. if anything I would build a "test pipe". An exhaust shop will not remove the cat for you and let your drive off. There is too big of a fine for their business to take the chance. See if you can find a place that buys old cats. Find the cat for an 85 and cut off the flanges, then weld in pipe. The 85 cat bolts in and out. When I had my 85, I would take it to the track and replace the cat with my test pipe. The pipe plus March underdrive pulleys was worth 1/2 second at the track.
...not the cat. if anything I would build a "test pipe". An exhaust shop will not remove the cat for you and let your drive off. There is too big of a fine for their business to take the chance. See if you can find a place that buys old cats. Find the cat for an 85 and cut off the flanges, then weld in pipe. The 85 cat bolts in and out. When I had my 85, I would take it to the track and replace the cat with my test pipe. The pipe plus March underdrive pulleys was worth 1/2 second at the track.
Melting Slicks
Joined: Jan 2008
Posts: 2,054
Likes: 120
From: AZ
LOL I have never had enough power!
I mentioned the federal EPA fine not in judgement, but to inform others of an expo$ure some may unaware of. I've run w/o one while fixing an extreme rich mixture, which will ruin a cat.
I saw virtually no improvement in performance WITH the stock CAT.
I mentioned the federal EPA fine not in judgement, but to inform others of an expo$ure some may unaware of. I've run w/o one while fixing an extreme rich mixture, which will ruin a cat.
I saw virtually no improvement in performance WITH the stock CAT.
Thread Starter
Instructor
Joined: Aug 2014
Posts: 185
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LOL I have never had enough power!
I mentioned the federal EPA fine not in judgement, but to inform others of an expo$ure some may unaware of. I've run w/o one while fixing an extreme rich mixture, which will ruin a cat.
I saw virtually no improvement in performance WITH the stock CAT.
I mentioned the federal EPA fine not in judgement, but to inform others of an expo$ure some may unaware of. I've run w/o one while fixing an extreme rich mixture, which will ruin a cat.
I saw virtually no improvement in performance WITH the stock CAT.