1998 Durango, 360, 4x4.

I know that the plenum gasket has been fixed twice in it's 130K life so far and it's failed again so I'm planning to do it this last time myself using shorter bolts.

While I am doing the plenum gasket I intend to clean / replace the plugs and check the O2 sensors. Wires and cap / rotor are already new.

Anyway, I'm wanting to do something about the CAT. Instead of just ramming a rod down the pipe to gut it...I want to just delete it. But that brings up an interesting choice:

Should I delete the CAT altogether or should I buy and install a high flow CAT?

Also, IF I get a code from deleting the CAT, what's the fix for that?

Thanks.

 

if you get rid of the cat you WILL get a code, they make O2 simulators which are supposed to eliminate the light but they dont tend to work very well in my experience.

also why do you want to get rid of the cat is it bad? clogged? whats the reasoning behind it, i only ask bc dodge put a high flow cat on these trucks in the factory, unless something goes wrong there is 0 reason to replace it or remove it.

also use the hughes engines plenum kit, it is a replacement plate and permanent fix, you must be simply replacing it with the mopar parts.

 

I performed the test where you remove the pre-CAT sensor and see if it changes flow / engine RPM dramatically and it was surely noticeable. Knowing that I have had issues with the plenum in the past, which has led to fouled plugs and that leads to clogged CAT...I am sure I need at least a new CAT or a gutted CAT.

The cost of a new CAT is considerable. Same for the after market high flow CATs. A much cheaper option is to remove it and the only reason I was contemplating that was because I had heard rumor of a solution to the code.

I've looked at the aluminum plate and I can make one here at work if I need one. However, I am of the mindset that I don't need to bother. Shorter bolts that won't bottom out in the aluminum are the fix I am going to try first.

If that fails too, then I will look into the aluminum plate. I have just read too many times that the shorter bolts don't have to be re-repaired to justify the cost of the aluminum plates, or the effort to make my own.

 

Good luck with the shorter bolt idea... i have read all sorts of crazy fixes with the plenum gasket over the years and all have failed and ended up installing the kit. Just remember the cheaper the fix, the cheaper the outcome... personally i would just do the kit and all it a day but, each there own.

 

I understand the concept of what's going wrong, trust me I do. Steel plate under an aluminum manifold, and the expansions and contractions are different during the heating and cooling cycles. I get how that quickly wears the gasket and you get a failure.

I also know that with that many bolts holding the two together that something else must be issue and I think...I will verify this during the project, that the bolts are simply bottoming out right at the point of compression but aren't allowing any crush of the gasket. It seals for a bit, then fails.

There are just too many other places where different metals that expand and contract differently survive amazingly long times with no issues. Steel timing covers, maybe aluminum, on an iron block. Aluminum heads on iron blocks. Aluminum water pumps on iron blocks. Steel bearing caps in aluminum differentials. Just to name a few.

They all hold something in common, they they are different metals yet don't experience such a common gasket failure as the plenum pan on the bottom of the intake.

I'm thinking some over sized washers and shorter bolts, all torqued properly without bottoming out, and that gasket won't be going anywhere for a long time.

If I'm wrong I'll freely admit it and gladly change out the steel pan for an aluminum plate.

 

CAT should only be 300-400 bucks I just bought one that is CARB certified on the http://www.magnaflow.com/02catalytic...FQkaQgodzVMtWg

 

Now please explain this.....


Why the hell would someone living in Missouri such as the OP wanna spend the extra money to put on a California cert cat on there vehicle when they can put on the federal cert cat for half the cost??

Second why would you wanna go though the expense of a new cat when the old one works fine... These truck come factory with a high flow cat and as long as there are no codes or it is not causing a issue there is no reason to replace it.

Please let's think about what we are doing before we spend money and not go full retard from the beginning

 

Well didnt know he lived in Missouri, secondly 400 bucks is not pricey unless your welfare checking it,
third why they heck was he talking about his cat in the first place about punching holes so on.
Lastly just remove the damn thing Missouri Emissions laws are no where near as tough as CA laws are.

So before you state full retard maybe you need to look at the posters comments like i said punch a pipe thru a cat indicates what? lets think...

Just do what i did buy a cat make sure there flanged connections get a bypass joining pipe flanged connections go Dual exhaust and pop the cat in when you need to do a smog check. Simple sh*t,

But hey you might be the Dodge Durango God, You seen my truck lets see yours.

 

Don't insult me with Welfare comments, please, but $400 is a big amount for me to spend in one chunk when it doesn't relate to mortgage, monthly bills, food, or expenses. Heck $200 on a part is a monthly privilege.

Get this clear...I pulled the pre-CAT O2 sensor, and the flow improved. That means the CAT is somewhat clogged, at least up to or before the computer notices something.

That tells me something has to be done. I have a few options:

#1 - Gut the CAT.
#2 - Remove the CAT.
#3 - Replace with stock CAT.
#4 - Replace with higher flow CAT.

Seems there may be a computer code issue with options #1 and #2 so I'm inclined to discount those.

Can someone please suggest options for a CAT that flows better than stock if you've used and liked one. Performance is always a plus and MPG has been so bad I don't really care if it gets a little worse.

If I find no suggestions...I'll replace it with a stock replacement part and be done with it. I'm doing the Plenum fix this weekend, along with a few other odds and ends, and this will be the best time to do it.

 

www.rockauto.com... they have the OEM ones for around $200 give or take.