89 Pre CATS
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From: The Ham AL
89 Pre CATS
Called an exhaust shop about cutting out my pre catallitic converters and putting straight pipes in, but they didn't even hesitate in saying "NO WAY JOSE!, I ain't payin a $10k fine."
I did this because there is a knocking sound coming from them while idle. Many auotomotive mechanically inclined guys have told me to get rid of those pre cats. Well, my options now are to purchase a new exhaust (which I am not doing) or take the exhaust off myself, cut out the pre cats, and get a friend to weld a pipe section into the gap.
I just keep thinking that there has got to be someone on this earth who has designed a pipe section to fit perfectly and if I added some band clamps this whole thing would be fixed.
I did this because there is a knocking sound coming from them while idle. Many auotomotive mechanically inclined guys have told me to get rid of those pre cats. Well, my options now are to purchase a new exhaust (which I am not doing) or take the exhaust off myself, cut out the pre cats, and get a friend to weld a pipe section into the gap.
I just keep thinking that there has got to be someone on this earth who has designed a pipe section to fit perfectly and if I added some band clamps this whole thing would be fixed.
Team Owner
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From: Bergen County, NJ Democrats, doing for the country what they did for Michigan
Called an exhaust shop about cutting out my pre catallitic converters and putting straight pipes in, but they didn't even hesitate in saying "NO WAY JOSE!, I ain't payin a $10k fine."
I did this because there is a knocking sound coming from them while idle. Many auotomotive mechanically inclined guys have told me to get rid of those pre cats. Well, my options now are to purchase a new exhaust (which I am not doing) or take the exhaust off myself, cut out the pre cats, and get a friend to weld a pipe section into the gap.
I just keep thinking that there has got to be someone on this earth who has designed a pipe section to fit perfectly and if I added some band clamps this whole thing would be fixed.
I did this because there is a knocking sound coming from them while idle. Many auotomotive mechanically inclined guys have told me to get rid of those pre cats. Well, my options now are to purchase a new exhaust (which I am not doing) or take the exhaust off myself, cut out the pre cats, and get a friend to weld a pipe section into the gap.
I just keep thinking that there has got to be someone on this earth who has designed a pipe section to fit perfectly and if I added some band clamps this whole thing would be fixed.
Done.
Le Mans Master
Joined: Jun 2006
Posts: 5,642
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From: One day you're a Comet...the next day you're dust... Arkansas
Called an exhaust shop about cutting out my pre catallitic converters and putting straight pipes in, but they didn't even hesitate in saying "NO WAY JOSE!, I ain't payin a $10k fine."
I did this because there is a knocking sound coming from them while idle. Many auotomotive mechanically inclined guys have told me to get rid of those pre cats. Well, my options now are to purchase a new exhaust (which I am not doing) or take the exhaust off myself, cut out the pre cats, and get a friend to weld a pipe section into the gap.
I just keep thinking that there has got to be someone on this earth who has designed a pipe section to fit perfectly and if I added some band clamps this whole thing would be fixed.
I did this because there is a knocking sound coming from them while idle. Many auotomotive mechanically inclined guys have told me to get rid of those pre cats. Well, my options now are to purchase a new exhaust (which I am not doing) or take the exhaust off myself, cut out the pre cats, and get a friend to weld a pipe section into the gap.
I just keep thinking that there has got to be someone on this earth who has designed a pipe section to fit perfectly and if I added some band clamps this whole thing would be fixed.
My muffler shop just cut them out and welded in short peices of 2 1/4" pipe. No inspection here. Cost me $50.
Race Director
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From: Overland Park Kansas
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Pick the 2.5" version and consider installing a new, hi-flow main cat. Any cat-back (including elims) would round-out the upgrade. (You should know the exhaust manifolds have 2.5" outlets and transition down to 2.25" pipe. Does that give you a clue?)
There's some hp to gain from the swap.
gp
Oh yeah, check with other shops too. Not all shops are so BTB. If a shop needs "encouragement", tell them you'll install a new 3-stage hiflow main to replace the 2-stage version that's WAY outdated.
Last edited by GREGGPENN; Mar 25, 2008 at 11:36 PM.
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From: The Ham AL
Yes, I was thinking about this but I can't see the CAT for the heat sheilds. Is there a port of some sort or do you take the CAT off and reem it out?
Slingshot
Joined: Dec 2001
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From: Charlotte NC
Good luck.
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Le Mans Master
Joined: Oct 2003
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From: seattle WA
Last time I did one, I just removed it, took a heavy piece of pipe, slid it in as far as I could get it and hammered the heck out of it. It all broke apart and was easy to shake out. Re-installed it...now hollowed out.
Race Director
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From: Overland Park Kansas
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From: The Ham AL
When you reemed out the CATs, did you cut the heat shield off and then just leave it off afterwards?
Also, what is the connection like from the pipes to the CAT? It feels welded. If it is, then I am assuming you cut off the CAT and reemed it and then welded it back in place. Otherwise you would have had to buy a fitting and could clamp it back in place.
Just a little more info would be nice. Thanks.
Le Mans Master
Joined: Jun 2006
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From: One day you're a Comet...the next day you're dust... Arkansas
Aight. I looked at the CATs again tonight. A friend went by the local auto parts store today and said that they sell exhaust fittings that could be put in if we were to cut them out. However, the CAT heat sheild looks and feels like one piece. I didn't notice any rivets or welds.
When you reemed out the CATs, did you cut the heat shield off and then just leave it off afterwards?
Also, what is the connection like from the pipes to the CAT? It feels welded. If it is, then I am assuming you cut off the CAT and reemed it and then welded it back in place. Otherwise you would have had to buy a fitting and could clamp it back in place.
Just a little more info would be nice. Thanks.
When you reemed out the CATs, did you cut the heat shield off and then just leave it off afterwards?
Also, what is the connection like from the pipes to the CAT? It feels welded. If it is, then I am assuming you cut off the CAT and reemed it and then welded it back in place. Otherwise you would have had to buy a fitting and could clamp it back in place.
Just a little more info would be nice. Thanks.
Team Owner
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
The pre-cats have an integral heat shield that is part of the shell. If you cut the pre-cats off, the straight pipe sections will not have anywhre near as much heat build-up.
Having somebody cut the pre-cats and weld in new pipe is an option, but you will have to at least tack the pipes in place to get everything lined up properly. Then you can remove the Y-pipe again and finish welding. On my 87, the front Y-pipe and main cat are a slip-fit and clamped together.
I have the M-A front Y-pipe without the pre-cats but I havent installed it yet. The outside diameter of the big end of the Y-pipe is 3" which is typical of most main cats.
The rear portion of the main cat is a ball-type flange and it attaches to the rear exhaust pipe with two bolts.
You could buy a high-flow cat to replace the stock one, but there are two types; one has a fitting for the AIR tube and another one does not. If you have the AIR pump on the car, then get the version with the tube fitting. If you don't have the AIR pump or are planning on removing it, the tube at the car can easily be blocked off.
Having somebody cut the pre-cats and weld in new pipe is an option, but you will have to at least tack the pipes in place to get everything lined up properly. Then you can remove the Y-pipe again and finish welding. On my 87, the front Y-pipe and main cat are a slip-fit and clamped together.
I have the M-A front Y-pipe without the pre-cats but I havent installed it yet. The outside diameter of the big end of the Y-pipe is 3" which is typical of most main cats.
The rear portion of the main cat is a ball-type flange and it attaches to the rear exhaust pipe with two bolts.
You could buy a high-flow cat to replace the stock one, but there are two types; one has a fitting for the AIR tube and another one does not. If you have the AIR pump on the car, then get the version with the tube fitting. If you don't have the AIR pump or are planning on removing it, the tube at the car can easily be blocked off.
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From: The Ham AL
Well, being tired of waiting and the lack of funds...I broke out the hack saw today. I got one pipe sawed through and the other about 75%. Once I get the other pipe cut, I plan on unbolting the exhaust from the engine and doing the other 2 cuts off the car. Cutting those suckers on the car is a fairly tough task with the lack of room under there under ramps.
Then, I will try and find pipe and fittings to patch it up later. If I am unsuccessful in a "bubba" job, I will break down and purchase a new "Y" pipe without CATs.
We'll see.
Then, I will try and find pipe and fittings to patch it up later. If I am unsuccessful in a "bubba" job, I will break down and purchase a new "Y" pipe without CATs.
We'll see.
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From: The Ham AL
Not a bad idea 65Z01. I did finish the second cut and I will be taking the pipes off the engine this week to make the other cuts. My fingers are crossed that I can line the pipes up for a straight run of pipe. I didn't cut the pipes right at the CAT. I back up some so that I can cut out the bend. The bubba job is underway. I will be changing out the O2 sensor while in there.
Thanks for the help Siveck.
Thanks for the help Siveck.
Pro
Joined: Jan 2008
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From: Near Lockport NY Black 1986 Coupe
If you can find someone who knows how to do it, you can drill out the pre-cats and leave them on so it looks like normal but it actually lets the air flow through like straight pipes. Might be less work than finding a replacement pipe and spending the time to cut it all out and weld.
Instructor
Joined: May 2001
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From: Raleigh NC
Sorry I'm a little late to this dance but what I did, and it worked real well was to cut the pipe about 1" past the rear of the precat and then chopped out the honeycomb inside that is rattling around. Then I had a welder weld the pipe back together for me.
The trick to this whole thing to get it aligned right is to drill two small (1/16" is fine) in each side of where you are going to cut the pipe so they can be used as orientation marks when it is welded back together.
I just took the pipes to the welder and asked him if he would weld it for $20 and all he had to do was align the two drilled holes to get the orientation right. 5 minutes and I was out of there.
The smog inspectors were none the wiser.
The trick to this whole thing to get it aligned right is to drill two small (1/16" is fine) in each side of where you are going to cut the pipe so they can be used as orientation marks when it is welded back together.
I just took the pipes to the welder and asked him if he would weld it for $20 and all he had to do was align the two drilled holes to get the orientation right. 5 minutes and I was out of there.
The smog inspectors were none the wiser.
Pro
Joined: Oct 2003
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From: Savannah GA
From experience, if the pre-cats are rattling do something before they break up and plug the main converter and your making it home at about 45mph!
Take the entire exhaust off the car. The manifold bolts are the only worry, if they come off everything else is cake. The rear of the main cat has a bolt flange to seperate it from the mufflers. Getting the front y pipe off the main cat might be tough since the later systems have a slip joint and clamp, mine had pinched a grove and it was a pain to get apart. I didn't spend anything but a couple hours out back. Get a piece of scrap 1/2 steel pipe about 4ft long it will bend around enough to get down in there and bust up the matrix.
You might be suprised how much "muffler" a converter is!
JS
Take the entire exhaust off the car. The manifold bolts are the only worry, if they come off everything else is cake. The rear of the main cat has a bolt flange to seperate it from the mufflers. Getting the front y pipe off the main cat might be tough since the later systems have a slip joint and clamp, mine had pinched a grove and it was a pain to get apart. I didn't spend anything but a couple hours out back. Get a piece of scrap 1/2 steel pipe about 4ft long it will bend around enough to get down in there and bust up the matrix.
You might be suprised how much "muffler" a converter is!
JS