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Catalytic Converter Removal

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Fahques View Drop Down
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    Posted: Jul/15/2017 at 11:40am
I have a 1982 Concord wagon, 258, V6, auto trans. The muffler recently cracked & needs to be replaced. The muffler is welded to the connecting pipes. Since I would have to cut the pipes to replace the muffler, I was thinking about replacing everything from the header pipe to the end and removing the CC and putting in a glass pack with as much straight pipe as possible.

This is my first AMC and what I'm not sure about is if by doing so I am going to mess up the way the car runs by messing with all the 'innovative' emissions stuff or vacuum lines or oxygen sensors or anything else.

I guess my question is, can I just remove the exhaust and beef it up with new pipes and a loud muffler ?


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Post Options Post Options   Thanks (0) Thanks(0)   Quote 73Gremlin401 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 1:09pm
Originally posted by Fahques Fahques wrote:

I have a 1982 Concord wagon, 258, V6, auto trans. The muffler recently cracked & needs to be replaced. The muffler is welded to the connecting pipes. Since I would have to cut the pipes to replace the muffler, I was thinking about replacing everything from the header pipe to the end and removing the CC and putting in a glass pack with as much straight pipe as possible.

This is my first AMC and what I'm not sure about is if by doing so I am going to mess up the way the car runs by messing with all the 'innovative' emissions stuff or vacuum lines or oxygen sensors or anything else.

I guess my question is, can I just remove the exhaust and beef it up with new pipes and a loud muffler ?


IMHO, AMC 6cyls with the pulse-air system need the catalyst to operate properly.  Question is, does your car have pulse air.  It's easy to spot on the catalyst - there will be a roughly 5/8" diameter pipe running from it back up to the engine. If your engine is stock, and everything else emissions wise is in place and operating properly, I'd recommend replacing the catalyst when you do the rest of the exhaust system. 

If however, you don't have pulse-air, or do but a lot of the system is missing/butchered up, whatever, and you don't have emissions testing in your area, then by all means get rid of it, and finish cleaning up the remnants that may exist under the hood. 

Note that some of the stuff, EGR, PCV, and TAC are all good things, and if in proper condition with no vacuum leaks and good valves, really do make your stock 6 run a lot smoother, and I'd recommend leaving them in place, or repairing as needed.

In general, AMC did a better job with emission controls than the big 3 did on the 6 in the late 70s and 80s, with regard to general driveability.  Sometimes stock is better, and if your motor is as delivered from the factory, keeping the emissions stuff as close to OEM as possible is actually a good thing.

Again, just my opinion, I'm sure there will be plenty others!!
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Post Options Post Options   Thanks (1) Thanks(1)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 2:55pm
Originally posted by 73Gremlin401 73Gremlin401 wrote:


Note that some of the stuff, EGR, PCV, and TAC are all good things, and if in proper condition with no vacuum leaks and good valves, really do make your stock 6 run a lot smoother, and I'd recommend leaving them in place, or repairing as needed.

In general, AMC did a better job with emission controls than the big 3 did on the 6 in the late 70s and 80s, with regard to general driveability.  Sometimes stock is better, and if your motor is as delivered from the factory, keeping the emissions stuff as close to OEM as possible is actually a good thing.
You'll get a big "amen" from me on that. GM did a pretty good job, too. My 1977 Buick runs really good with all its stock stuff. Of course, AMC used a lot of Rochester (GM) emission control parts. 

You won't notice any performance increase by using a straight-through glasspack muffler instead of the stock type chambered (also called turbo) muffler. With the correct size pipe (2" is plenty) just about any muffler will flow more than you need. All you'll do with the glasspack is make your early 80s luxury car sound like a rice burner, but without the performance to show for all the noise. 

Converters also help make the car quieter, and if they are properly sized and in good condition they have essentially zero impact on performance. That being said, a clogged old converter will murder your performance, and old carbureted engines are dirty enough that they tend to clog up their converter pretty quickly.

2" exhaust pipe, Thrush or Walker turbo muffler, downturned tip. It makes for quiet exhaust, but you get a nice low rumble at idle. It sounds respectable. 
'66 Marlin: 327/T10/3.54 Twin Grip
'72 Wagoneer: 360/TH400/3.31
'73 Ambassador: 360/TF727/3.15
'77 Hornet: 232/TF904/2.73
'84 Eagle: 258/TF904/2.73
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Post Options Post Options   Thanks (0) Thanks(0)   Quote scott Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 3:51pm
You'll need the catalytic convertor in place to get your Concord to pass the state inspection in Pennsylvania. Unless you have it registered as an antique car.  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pacerman Quote  Post ReplyReply Direct Link To This Post Posted: Jul/15/2017 at 3:54pm
Those old pellet converters lose their pellets over time so if you tap on your converter it may sound hollow, meaning that it is empty.  If you are subject to a visual inspection (only) to pass the "emissions" test, I would leave it in place.  Joe
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Jul/16/2017 at 2:06am
^ Yep. If I had a car with a pellet cat, I'd pull the drain plug and let all the pellets out, then sell them for platinum. 

People do the same with monolith cats, though there isn't much reason to. A good monolith cat doesn't restrict unless the engine is out of tune and plugs it up...which a lot are. 


'66 Marlin: 327/T10/3.54 Twin Grip
'72 Wagoneer: 360/TH400/3.31
'73 Ambassador: 360/TF727/3.15
'77 Hornet: 232/TF904/2.73
'84 Eagle: 258/TF904/2.73
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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomslik Quote  Post ReplyReply Direct Link To This Post Posted: Jul/16/2017 at 8:32am
Originally posted by FSJunkie FSJunkie wrote:


^ Yep. If I had a car with a pellet cat, I'd pull the drain plug and let all the pellets out, then sell them for platinum. 

People do the same with monolith cats, though there isn't much reason to. A good monolith cat doesn't restrict unless the engine is out of tune and plugs it up...which a lot are. 





and if it were me, i'd put a new monolithic cat on it and forget the muffler....legal and you won't get the muffler shop fined
67 american 290/4speed
73 hornet X 360/auto



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Post Options Post Options   Thanks (1) Thanks(1)   Quote amcfool1 Quote  Post ReplyReply Direct Link To This Post Posted: Jul/16/2017 at 1:07pm
hi, in 82 there was no "pulse air" system, that didn't come 'till 84. 82 should have an "air injection" cat, ie, still using an air injection (smog) pump. those tubes tend to rust out, and are no longer available, so, unless you fab your own, best to go with a NON injection cat. new cats are not very restrictive, (or that expensive) and will keep you legal. i HIGHLY recommend you keep a cat. converter. Unless you have a working air injection system, replace the cat. converter, without it's air injection, it can overheat (or not, but why take a chance) and roast your carpet and may even start a fire, the newer ones are much better, good luck, gz
ps, love to see that 258 V6!:)
george z
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Post Options Post Options   Thanks (0) Thanks(0)   Quote purple72Gremlin Quote  Post ReplyReply Direct Link To This Post Posted: Jul/16/2017 at 2:53pm
On certain cars, the EGR needs backpressure to open.  (some GM cars did)  AMC used Delco EGR valves, (althrough I have a AMC 360 with the Chrysler EGR valve)....   and usually if you keep everything working and hooked up correctly, it will run good.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Jul/16/2017 at 3:20pm
Originally posted by purple72Gremlin purple72Gremlin wrote:

On certain cars, the EGR needs backpressure to open.  (some GM cars did)  AMC used Delco EGR valves, (althrough I have a AMC 360 with the Chrysler EGR valve)....   and usually if you keep everything working and hooked up correctly, it will run good.
Yeah, he almost certainly has a positive backpressure EGR valve. Most AMC engines got them from 1976 onwards. The more backpressure it has, the more exhaust it recirculates, so less backpressure due to a higher flowing exhaust would simply mean less EGR. That's not necessarily a bad thing. 

I wouldn't worry about throwing off the EGR with an exhaust change. I have two engines with positive backpressure EGR: one is a 1977 AMC 232 I6 and another is a 1977 Buick 231 V6. I drove both of them with their stock exhaust systems (both 2" systems with converters) then I drove them again with improved, higher flow exhaust systems (2" or 2.25" with no cat) and noticed zero change in performance or how the EGR operated. I've even driven them with no EGR what so ever and they didn't ping or have any ill effects. Some engines will ping without their EGR unless the timing and fuel mixture are changed, but mine never have. 
'66 Marlin: 327/T10/3.54 Twin Grip
'72 Wagoneer: 360/TH400/3.31
'73 Ambassador: 360/TF727/3.15
'77 Hornet: 232/TF904/2.73
'84 Eagle: 258/TF904/2.73
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