removing AIR system and cat

[mattchester]

I had great plans to keep my 85 GW as stock as possible. I went so far as to buy a salvage yard air pump, I was going to replace any bad check valves, etc.,
Until I realized that all the air tubes were completely rotted out. Every check valve shot, and the pipe to the cat was disconnected, and rusty.
I dont live in a smog contol county so I am just going to plug the holes in the manifolds with bolts. I figure that if I put plenty of anti-sieze on them it will be easy to replace the air system in the future.
My cat is caked in concrete-like mud. I assume it is shot as well.
Will it hurt to remove the cat altogether, will it negatively affect engine performance without it?
I want to spend as little as possible to get this thing on the road, but I still want it to run well.

[FSJ Guy]

I'd leave the cat alone. Unless it's clogged, in which case you should replace it.

You will smell funny without a cat. OK, your TRUCK will smell funny.

[1jeep4me]

Here in Texas my 82 has to visually check out with a cat. I also pulled the air pump and blugged the air holes etc.

I also shattered the ceramic cat cone inside and run to a chevy truck muffler that dual. Thats was when it was sold. It ran cool and ran well and the exhaust smelled like a muscle car from the 70's

Fast forward to when I just got her back.

I sold it 6 years ago and just bought it back. during this time the PO added a cat and it frankly sucks but.

I have plans of doing a throley exahust system and using a nice high flow cat.

to answer your question. It will run better on the top end and will lose bottom end because your stock 2v will need to be rejetted etc.

I have a perfromer non egr intake and performer 4v carb.

[HerrKooled]

If anything, you would gain a MPG or 2 and make a couple horse more if you removed it. It all comes down to your states emission laws, and if you have them.

[Tigger4X]

WHy yank the cat and then have to pop in a new piece of pipe. If anything hollow the bugger out just in case you have to pass a visual. You can plug the air rails and make them look like they are functional, and maybe even go so far so to leave the air pump on and make the pulley free spin without turning the internals.

[mattchester]

So, I'd lose some low end?

to answer your question. It will run better on the top end and will lose bottom end because your stock 2v will need to be rejetted etc.
.

I am trying to keep it cheap. I like the idea of hollowing the cat out, if it is in fact clogged,
I really dont want to have to bother with rejetting, being at altitude, extreme cold (-20) and heavy snow. I seem to be running well now. (Ask me again in January )
I have no emissions inspections so I dont have to worry. I just want cheap and reliable.
Maybe I'll just leave the cat alone. But, every air tube was broken and caked in soot. Every check valve was bad, and the Y tube has a hole in it. I think I can fix the Y tube, but I'm woried that the exhaust wont be able to flow freely (and loudly) through all the leaks that that were present.
I probably would prefer more on the high end, if I had a choice. Mountain passes are tough.
So, if it is clogged, can I just hollow it out somehow? Will I be OK?

[dbuie]

You can hollow out your cat just like we did back in the eighties with our stangs. Take off car and beat out the guts. If your cat is that bad then chances are your muffler is clogged up with debris from the cat too.

Went to have my cat replaced last year and when they held it up chunks of debris fell on the floor. Took off the muffler and the same thing happened. So, I replaced both. Felt like I gained 20 HP afterward.

[Rich88]

If the cat is not clogged, if you leave it in place and don't have a functioning AIR system, it will be clogged. It may be partially clogged already. The air in the exhaust stream and into the cat assists in burning off unburned fuel and raising the cat temp high enough to work properly. Without that fresh air blast, soot will accumulate on the honeycomb of the cat.

If you would go through the trouble of removing the cat and smashing its guts out, you may as well replace it with a nice clean pipe. Otherwise, standing downwind of a cat-less FSJ will cause your eyes to water.

[Tigger4X]

If the cat is not clogged, if you leave it in place and don't have a functioning AIR system, it will be clogged. It may be partially clogged already. The air in the exhaust stream and into the cat assists in burning off unburned fuel and raising the cat temp high enough to work properly. Without that fresh air blast, soot will accumulate on the honeycomb of the cat.

After having read what he posted of the condition of the AIR system his cat is trashed! It is possible that his muffler is too, but I'm betting the cat is so packed up that it hasnt gotten there.

If you would go through the trouble of removing the cat and smashing its guts out, you may as well replace it with a nice clean pipe. Otherwise, standing downwind of a cat-less FSJ will cause your eyes to water.

The stated purpose for leaving the cat in place, although hollowed out, is so that it passes a under truck visual inspection if ever needed. Replacing it with pipe would be a good idea if he doesnt want to have to buy one in the future just for a visual.



Once you remove the cat you can use a number of long items to jab at the innards and they will begin to fall out once you turn it upside down to empty the junk, then begin again until it begins to fall out the other end while you smash away at the guts from the top.

[1jeep4me]

Tigger, I got to ask, does or has anybody here seen a actually clogged cat? The only time I have seen one was from oil burning ringless motors .

I dont doubt I just have never seen one in my years.

The reason I ask is because the cat needs heat to become a catylst to activate the reaction of gas. Otherwise it still flows it just does not convert the gas. The air pump usually are injected mid stream or mid flow to cool the gas off after the reaction.

This is what I was told I am willing to learn.

After having read what he posted of the condition of the AIR system his cat is trashed! It is possible that his muffler is too, but I'm betting the cat is so packed up that it hasnt gotten there.



The stated purpose for leaving the cat in place, although hollowed out, is so that it passes a under truck visual inspection if ever needed. Replacing it with pipe would be a good idea if he doesnt want to have to buy one in the future just for a visual.



Once you remove the cat you can use a number of long items to jab at the innards and they will begin to fall out once you turn it upside down to empty the junk, then begin again until it begins to fall out the other end while you smash away at the guts from the top.

[Rich88]

I have seen a clogged cat. It was mine.

I bought a new cat, new air pump and air injector manifolds....and passed emissions in flying colors.

I went home, took off the air pump and all the air injector stuff, & blocked the exhaust air ports with bolts... all to get my extra 5 hp or so. But I left the cat in place.

Three years later, my performance nose-dived and behold my cat was clogged enough to render enough back pressure to cause the problem. After research I found out why....which is why I preach give the cat AIR or remove it.

[1jeep4me]

But the reason was? The air pump pumps cool air in to the mid section cooling outflow gases or does the air pump pum air in the mid section to allow fresh air to burn?
Pumped air injection
Pumped air injection systems use a vane pump turned by the engine via a belt. The pump's air intake is centrifugally filtered by a rotating screen to exclude dirt particles large enough to damage the system. Air is delivered under pressure to the injection point(s). A check valve prevents exhaust forcing its way back through the air injection system, which would damage the pump and other components.
Carbureted engines' exhaust raw fuel content tends to spike when the driver suddenly releases the throttle. To prevent the startling and potentially damaging effects of the explosive combustion of this raw fuel, a diverter valve is used. This valve senses the sharp increase in intake manifold vacuum resulting from the sudden closure of the throttle, and diverts the air pump's outlet to atmosphere. Usually this diverted air is routed to the engine air cleaner or to a separate silencer to muffle objectionable pump noise. Aspirated air injection
Air injection can also be achieved by taking advantage of the negative pressure pulses in the exhaust system at engine idle. A sensitive reed valve assembly called the aspirator valve is placed in the air injection plumbing, which draws its air directly from the clean side of the air filter. During engine idle, brief but periodic negative pressure pulses in the exhaust system draw air through the aspirator valve and into the exhaust stream at the catalytic converter. This system, marketed as Pulse Air, was used by American Motors, Chrysler, and other manufacturers beginning in the 1970s. The aspirator provided advantages in cost, weight, packaging, and simplicity compared to the pump, but the aspirator functions only at idle and so admits significantly less air within a significantly narrower range of engine speeds compared to a pump. This system is still used on modern motorcycle engines, e.g. the Yamaha AIS (Air Injection System).

This may be what is happening to a clogged converter:

Meltdown
Any condition that causes abnormally high levels of unburned hydrocarbons ? raw or partially-burnt fuel ? to reach the converter will tend to significantly elevate its temperature, bringing the risk of a meltdown of the substrate and resultant catalytic deactivation and severe exhaust restriction. Vehicles equipped with OBD-II diagnostic systems are designed to alert the driver of a misfire condition, along with other malfunctions, by means of the "Check Engine" light on the dashboard.


So what I see here is that if you take the air pump off you should prolly hawg out the cat too!

[Rich88]

The reason for the clogged cat was lack of fresh air to burn off unburned hydrocarbons, which accumulates as soot on the honey comb in the converter.

Concerning cat burn out, if perchance all is working OK and you have, say, a non-firing cylinder or a very rich condition allowing lots of raw fuel to exhaust, then the cat will overheat into meltdown as all that fuel burns off inside the cat. The cat is not designed to burn off much more than normally expected hydrocarbons without going into meltdown.

[shimniok]

Air injected into the cat during load condition (via the AIR diverter valve) helps catalyze the extra amount of unburned fuel; under low load, air is diverted to the exhaust manifolds instead.

[Tigger4X]

I have seen a clogged cat. It was mine.

I bought a new cat, new air pump and air injector manifolds....and passed emissions in flying colors.

I went home, took off the air pump and all the air injector stuff, & blocked the exhaust air ports with bolts... all to get my extra 5 hp or so. But I left the cat in place.

Three years later, my performance nose-dived and behold my cat was clogged enough to render enough back pressure to cause the problem. After research I found out why....which is why I preach give the cat AIR or remove it.

RICH88 ... Indeed, in your particular situation you killed your cat leaving it in place. If you had removed your cat when you removed everything else you would have been fine and saved your new parts for later use. HOWEVER ... the original post stated his stuff is trashed at this point, he doesn't want to spend the cash on stuff he has NO use for, and wants to know what options he might have. My comment was if there might be a remote possibility he could encounter a "visual inspection" under the truck that if the empty shell is present that he could potentially avoid that pitfall. If his cat was in good shape then yeah do what you can to preserve it but its NOT ... "its dead Jim, its dead." If he hollows out his DEAD cat only for that possible purpose then there is abGreat Googley MoogleyGreat Googley MoogleyGreat Googley MoogleyGreat Googley Moogleyely ZERO reason to "give the cat AIR". I dont understand what is so difficult to grasp here.