Put back on a Catalytic Converter... uggg

1161 Views 32 Replies 8 Participants Last post by JeepCJ, 13 d ago

PeterBishop

Discussion Starter · 16 d ago

Back to my 83, Nuttered, 258

I installed a "new" carter BBD without a stepper motor and the Jeep ran much better, but the CJ was missing a muffler....

So I removed the busted and rusted cat and the 1" pipe that went from the cat to the exhaust (maybe it's 3/4"). I installed a new muffler and did not replace the cat, leaving a open hole in the exhaust by the header... and the CJ was quieter, but ran horrible.

I took it to a car guy and he confirmed what I suspected that there was missing back pressure and he recommended that I put a cat back on.

Do you know what I call the 1" (or 3/4") pipe between the cat and the exhaust? I found a "universal" cat that has the port for about $150, but I don't know what to ask for about the small diameter pipe?

Thanks in advance, I really appreciate all y'all.

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keith460

· #2 · 16 d ago

If you did the "Nutter Bypass", you don't need the smaller pipe from the catalytic convertor for the upstream and downstream air injection system.
My replacement catalytic came with the same small pipe outlet but it is capped. I also run a Carter BBD without the stepper motor.

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KDub1984CJ7

· #3 · 16 d ago

Agreed; cut what was left of mine off and "JB Welded" a bolt in it when I nuttered...along with using a copper pipe cap and clamp (clamp not shown in pic) on the "upstream" tube by the exhaust manifold. So you could cap/plug or replace with a cat from an older CJ ('79 would work)

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Mayday-Joey

· #4 · 16 d ago

Not to throw a wrench in the whole thing but adding a cat back in to make it run better seems like a bad recommendation. it might be a simple out but would increased resistance "back pressure" in the exhaust actually make the car run better? I mean most people try to get rid of stuff like this to increase airflow, would this not be a tuning issue? Not a carb expert and in California so no cat isn't an option.

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PeterBishop

Discussion Starter · #5 · 15 d ago

Mayday-Joey said:
Not to throw a wrench in the whole thing but adding a cat back in to make it run better seems like a bad recommendation. it might be a simple out but would increased resistance "back pressure" in the exhaust actually make the car run better? I mean most people try to get rid of stuff like this to increase airflow, would this not be a tuning issue? Not a carb expert and in California so no cat isn't an option.

I'm trying to wrap my head around it too. Thanks

Reactions: 1

PeterBishop

Discussion Starter · #6 · 15 d ago

KDub1984CJ7 said:
Agreed; cut what was left of mine off and "JB Welded" a bolt in it when I nuttered...along with using a copper pipe cap and clamp (clamp not shown in pic) on the "upstream" tube by the exhaust manifold. So you could cap/plug or replace with a cat from an older CJ ('79 would work) View attachment 4187148 View attachment 4187149

I have the open hole on the lower photo. I was trying to figure out how to cap it without welding skills. Since there's no cat on now, I don't have that hole to plug. All I know is when I removed the cat and have the open hole, it ran worse.

PeterBishop

Discussion Starter · #7 · 15 d ago

KDub1984CJ7 said:
Agreed; cut what was left of mine off and "JB Welded" a bolt in it when I nuttered...along with using a copper pipe cap and clamp (clamp not shown in pic) on the "upstream" tube by the exhaust manifold. So you could cap/plug or replace with a cat from an older CJ ('79 would work) View attachment 4187148 View attachment 4187149

Where did you find a small clamp for the copper cap?

PeterBishop

Discussion Starter · #8 · 15 d ago

keith460 said:
If you did the "Nutter Bypass", you don't need the smaller pipe from the catalytic convertor for the upstream and downstream air injection system.
My replacement catalytic came with the same small pipe outlet but it is capped. I also run a Carter BBD without the stepper motor.

View attachment 4187029
View attachment 4187030

That makes sense, but the open hole I have is the one that KDub1984CJ7 has capped with the copper pipe cap.

KDub1984CJ7

· #9 · 15 d ago (Edited)

PeterBishop said:
Where did you find a small clamp for the copper cap?

OReilleys; just have them search "Pulse Air Tube" after they drill down to your year/make/model. They have a selection of sizes and I used the 1" model I believe.

So to make the copper cap fit as snug as possible I actually cut off about 1/2" of the end of the air pulse tube that attaches here and inserted it into the cap kinda like a bushing. The copper caps went fron 1/2" (too small) to 3/4" (too big) and I found that this setup snugged in there nicely. If someone was to located a 5/8" copper pipe cap it would probably be just right, but those seem to be not of the norm ( @JEEPFELLER can chime in here).

Also put some of the "exhaust glue/JB Weld" inside the cap, and "bushing" to help seal off any leaks prior to clamping it down.

PeterBishop

Discussion Starter · #10 · 15 d ago

KDub1984CJ7 said:
OReilleys; just have them search "Pulse Air Tube" after they drill down to your year/make/model. They have a selection of sizes and I used the 1" model I believe.

Pulse Air Tube is the name I've been looking for! Thanks!!

KDub1984CJ7

· #11 · 15 d ago

PeterBishop said:
Pulse Air Tube is the name I've been looking for! Thanks!!

, reread post with edits...I added some details that may be helpful for application.

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JeepCJ

· #12 · 15 d ago

What is your Jeep doing thats you feel like its running poorly. Generally speaking you should be able to make it run good with an open header (just stating the extreme not suggesting you do that).

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KDub1984CJ7

· #13 · 15 d ago

To his point, sorry got sidetracked by "oh, oh, I've done this!" 🙋...this shouldn't make it run bad. Pulse air tubes was the term that you were looking, check...now let's get it running better?

Like Keith was trying to point out, if it hasn't been Nuttered then the computer (MCU) could still be affecting things. Mainly could be jacking with your timing through vacuum advance.

Air Tube holes have to be plugged/capped on both ends, of both tunes. Injection point have been discussed, but what Air filter housing are you running? If OEM, are the points on the bottom of the housing capped (3/4" rubber caps from local parts store work great)

If those are checked off, (Nutter completed, timing reset, pulse air intake ports capped) I always look toward vacuum leaks, as they can be numerous...especially if you haven't had the chance to do a full clean up post Nuttered.

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pedal2themetai

· #14 · 15 d ago

HI,
I'm with Jeep CJ. removing the cat on a fully Nutter'ed motor should not change the way it run's. It sounds to me like the Nutter is not complete?

good luck take care be safe
tim

PeterBishop

Discussion Starter · #15 · 15 d ago

JeepCJ said:
What is your Jeep doing thats you feel like its running poorly. Generally speaking you should be able to make it run good with an open header (just stating the extreme not suggesting you do that).

As I noted in my original post, after I put on the "new" (good) carb, it ran much better.... then I took off the cat and pulse air tubes, replaced the exhaust pipe off the manifold (with the open pulse air hole), and installed a muffler. The jeep bogged down quite a bit. (noticeably different than before I messed with the exhaust)

So it went from a cat with pulse air connected, no muffler, to an open pulse air hole with a muffler and tail pipe.

I didn't make any adjustments to the carb or timing.

I just took it to an "old guy" that has a shop and he said it needed back pressure and I should put a cat on. Does that make any sense to you? It did to me in that something changed when I removed the cat and had the pulse air connected.

It's a bummer that all my gear head friends are back in California and I'm not "connected" in Nashville.... yet

KDub1984CJ7 said:
To his point, sorry got sidetracked by "oh, oh, I've done this!" 🙋...this shouldn't make it run bad. Pulse air tubes was the term that you were looking, check...now let's get it running better?

Like Keith was trying to point out, if it hasn't been Nuttered then the computer (MCU) could still be affecting things. Mainly could be jacking with your timing through vacuum advance.

Air Tube holes have to be plugged/capped on both ends, of both tunes. Injection point have been discussed, but what Air filter housing are you running? If OEM, are the points on the bottom of the housing capped (3/4" rubber caps from local parts store work great)

If those are checked off, (Nutter completed, timing reset, pulse air intake ports capped) I always look toward vacuum leaks, as they can be numerous...especially if you haven't had the chance to do a full clean up post Nuttered.

Thanks for sticking with me... it was my suspicion that it's vacuum related. I do have the original air cleaner on, and I know that there are vacuum lines all over the place. Some of them are most likely unnecessary after the Nutter.

pedal2themetai said:
HI,
I'm with Jeep CJ. removing the cat on a fully Nutter'ed motor should not change the way it run's. It sounds to me like the Nutter is not complete?

good luck take care be safe
tim

I agree... and vacuum leaks!

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PeterBishop

Discussion Starter · #16 · 15 d ago

JeepCJ said:
What is your Jeep doing thats you feel like its running poorly. Generally speaking you should be able to make it run good with an open header (just stating the extreme not suggesting you do that).

As I noted in my original post, after I put on the "new" (good) carb, it ran much better.... then I took off the cat and pulse air tubes, replaced the exhaust pipe off the manifold (with the open pulse air hole), and installed a muffler. The jeep bogged down quite a bit. (noticeably different than before I messed with the exhaust)

So it went from a cat with pulse air connected, no muffler, to an open pulse air hole with a muffler and tail pipe.

I didn't make any adjustments to the carb or timing.

I just took it to an "old guy" that has a shop and he said it needed back pressure and I should put a cat on. Does that make any sense to you? It did to me in that something changed when I removed the cat and had the pulse air connected.

It's a bummer that all my gear head friends are back in California and I'm not "connected" in Nashville.... yet

KDub1984CJ7 said:
To his point, sorry got sidetracked by "oh, oh, I've done this!" 🙋...this shouldn't make it run bad. Pulse air tubes was the term that you were looking, check...now let's get it running better?

Like Keith was trying to point out, if it hasn't been Nuttered then the computer (MCU) could still be affecting things. Mainly could be jacking with your timing through vacuum advance.

Air Tube holes have to be plugged/capped on both ends, of both tunes. Injection point have been discussed, but what Air filter housing are you running? If OEM, are the points on the bottom of the housing capped (3/4" rubber caps from local parts store work great)

If those are checked off, (Nutter completed, timing reset, pulse air intake ports capped) I always look toward vacuum leaks, as they can be numerous...especially if you haven't had the chance to do a full clean up post Nuttered.

Thanks for sticking with me... it was my suspicion that it's vacuum related. I do have the original air cleaner on, and I know that there are vacuum lines all over the place. Some of them are most likely unnecessary after the Nutter.

When I got this there were all kinds of unused plugs and ...

Vacuum lines, that I believe may not be necessary.

I'm wondering if I should go with a basic air filter and clean and plug vac lines that are not necessary.

As I'm learning the 2 big connections here are not hooked up and may have been connected to the pulse air system?

I do have some lines plugged, but I'm not sure which ones should go where? I was told that using a 77 vac hose diagram may be what I need to copy?

I took it to the "old guy" to sort out the vacuum lines and he tells me to get the Cat...now the more I think about it, I'm not sure that's correct?

Are the "3 vacuum solenoids used after the nutter?

I'd love to get my hands on photos of a 77's vacuum lines. To see what's not there and what is.

Should I get another air cleaner? without all the stuff on the stock one... (again, I'm thinking that most of the hoses on the stock air cleaner aren't necessary after the nutter)

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keith460

· #17 · 15 d ago

Close all the Pulse Air system connections with caps and rubber stoppers.

Get a 1980 or earlier year distributor with the Advance weights of 23R and 13R If I remember correctly. It's what I have. That way, the MCU doesn't adjust your timing like it did before.

Use this vacuum diagram post nutter:

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KDub1984CJ7

· #18 · 15 d ago

These need to be capped/plugged; when the pulse air tubes were hooked up to them they had 1 way valves only allowing fresh air to pulse OUT of here and be injected into the exhaust system. Now they are pulling unfiltered air IN to your carb and most likely affecting everything as a vacuum leak.

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PeterBishop

Discussion Starter · #19 · 15 d ago

Do I just ask for a distributor like that at an auto store?

I've heard about HEI distributors and really don't know what one is?

keith460

· #20 · 15 d ago

PeterBishop said:
Do I just ask for a distributor like that at an auto store?

I went to NAPA and purchased mine. I just told them I had a 1980 Jeep CJ-7 with the 258 I6 engine.

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