Replacement Catalytic Converter ?

[killian96ss]

I plan on replacing my stock cats when I hit 90k, and I'm wondering if Eastern Catalytic is the only one besides GM who makes a direct bolt in replacement for our trucks. Eastern Catalytic on E-bay

Does this one look right for our CC's?



I also found out that the pre-cat can't be removed in CA, and doing so will cause you to fail the visual inspection and the emission inspection. I have been told by a few SMOG shops that the pre-cat is there to help the secondary cat completely burn excess fuel, and that removing the pre-cat will shorten the life of the secondary cat and cause high emissions. This is why I have decided to find a complete bolt in replacement for both cats. After about 50k miles a catalytic converter will start to lose efficiency even though they will work ok to about 150k miles. I would bet that if I replaced mine right now @ 73k, I would get better gas mileage, however I am going to wait until 90k to justify the expense. My first SMOG check will be this November and i'm sure I will be @ 90k by then. BTW, a new GM system will set you back $700-$800.

Steve

[HenryJ]

That one is close , but i don't think it will bolt on. Ours has a "S" before and after the cat. The pipe sweeps up after a smaller precat and then sweeps down after the cat.
Another thing to watch for would be the Y-pipe. That one does not appear to be mandrel bent. Our Y-pipe is 1.9" Make sure your replacement is at least that.

I may be wrong, but the pipe and cat may be smaller as well. Our cat is a 3" in/out high efficiency converter That one may be 2.5"?

If your system is running good the cat should not degrade too rapidly. The cat is warranteed for 8yr/80,000mi at least. I just received a notice from Chrysler that their light truck systems are now covered for 120,000 miles.

I understand your CA restrictions, and am glad I am from a state with few restrictions.

I think if I were conserned with the system performance, prehaps investing in some test ports.
Weld threaded inserts before and after the cats. Then you can attach a gauge to test the system back pressure whenever you want to. Run SS plugs in them normally.
Readings in excess of 10 psi are bad. 5 psi is accpetable. A 2 psi difference is really good.
I think I would spend the money on the test ports and then have the offending component replaced as needed.

The idea of a bolt on system is nice, but not when I can have a cat replaced for under $200.

[killian96ss]

That one is close , but i don't think it will bolt on. Ours has a "S" before and after the cat. The pipe sweeps up after a smaller precat and then sweeps down after the cat.

I was wondering about those S-bends, but are they really neccesary for it to hook up correctly? It seems there is room to run straight back if the head pipes are shorter or don't drop down as much where the pre-cat is located.

Another thing to watch for would be the Y-pipe. That one does not appear to be mandrel bent. Our Y-pipe is 1.9" Make sure your replacement is at least that.

To be honest, I don't like the design of the stock Y-pipe or the replacement Y-pipe pictured. The merge point is not balanced and the entrance angles are kind of severe. If I didn't need the pre-cat I would almost certainly get this Y-pipe which is a far better design and would allow the exhaust pulses to be better balanced and increase flow as well.

The cat is warranteed for 8yr/80,000mi at least.

I will be at 80k in a couple of months which is why I am investigating possible replacements. Cats do degrade slowly just like 02 sensors, but as they do the performance and gas mileage will drop also.

I understand your CA restrictions, and am glad I am from a state with few restrictions.

The CA emission laws are way to strict. I could do so many more mods to the SS and CC if it weren't for these lame laws down here.

Weld threaded inserts before and after the cats. Then you can attach a gauge to test the system back pressure whenever you want to. Run SS plugs in them normally.
Readings in excess of 10 psi are bad. 5 psi is accpetable. A 2 psi difference is really good.
I think I would spend the money on the test ports and then have the offending component replaced as needed.

Excellent idea! I have seen the backpressure test kits on a couple of sites. Any recommendations for a good kit, or at least a good manufacturer?

Steve

[HenryJ]

...Excellent idea! I have seen the backpressure test kits on a couple of sites. Any recommendations for a good kit, or at least a good manufacturer?

That collector looks pretty good. I don't think our Y-pipes are all that bad when compared to earlier systems. The '96 S-series 2wd has a 1.5" Y-pipe and really looks restrictive. I think the stock Y-pipe will out flow the cats.

I haven't seen the kits, but i think that you could gather the components to build your own kit inexpensively. The gauge should be one that is not much over 1.5 times the needed operating pressure. I would say a 20-30 psi gauge would be good. Then a length of high pressure flexible tube attached in a length that is comfortable for viewing.

I wish I had thought of this when I deleted my precat. Not too hard to do though. I may drill a couple holes and cut a 1/8" black pipe union in half for welding to the exhaust pipes.

Link the kits, I would like to see what they are offering. I really haven't looked into this at all.

[killian96ss]

Here is one on E-bay. Waekon Exhaust Back Pressure Test Kit



Here is another from JC Whitney. Exhaust Back Pressure Test Kit



It appears the one from JC Whitney will also test the air injection system.

Steve

[HenryJ]

In order to bolt up to the stock system I do think those bends would be needed. After a 2" body lift there looks to be room to eliminate them, but that would mean modifying the y-pipe too, otherwise you would be running straight into crossmembers.

If you already have an old fuel pressure / vacuum gauge , that may work just fine. Mine only goes to 7 lbs , So I would be a bit nervous about using it.
The fittings should be cheap enough since they do not have to hold much pressure. Barbed fittings should work fine. Vacuum line tubing would probably work. You could probably use more expensive hose. In retrospect high pressure hose may be a waste of money.

I would be tempted to stop by the hardware store for a pump pressure gauge, or dig through that box of gauges for one with the correct range. Less is best and that 15 psi gauge is probably plenty.

$50 for a kit is probably not terrible, but the kit includes a bunch of connectors and attachments you may never use?

[Blackmobile]

This is probably unrelated but... I have a 02 Monte Carlo SS. On the way home from work my wife said it began to run rough, sputter and not accelerate... Bad cat... Originally GM warranteed it for 80,000 mis. of course we had 82,000 on the car. Just our luck, for a change, GM "just last wk" extended the mileage to 120K - bottom line we got a new cat for free.
You might check with local dealers to see if that was just the Monte's situation or if all cat coverage has been extended.

[killian96ss]

Most of the exhaust back pressure test kits seem to hook up directly to any of the 02 senors bungs, but I wonder if the engine would freak out while testing with an 02 sensor missing. I like your idea of installing extra bungs with plugs that could be removed for testing purposes. I would think the engine would run better this way since you are not disturbing the 02's. The only test gauge I have right now is on a fuel pressure tester, but this gauge reads all the way to 60 psi, and might not give me accurate results under 10 psi. For $42 the kit from JC Whitney doesn't seem all that bad.

Steve

[killian96ss]

Just our luck, for a change, GM "just last wk" extended the mileage to 120K - bottom line we got a new cat for free.
You might check with local dealers to see if that was just the Monte's situation or if all cat coverage has been extended.

Thanks for the info, and welcome to the site. I wonder if the 01-04 CC's will get the extended warranty on catalytic converters?

Steve

[HenryJ]

Blackmobile, I did not know GM was doing the same 120k warranty on cats. That must have been a federal mandate?

I have run mine without the right front O2 sensor and for a while without the rear O2 sensor connected. The front did not set a light, but was only run long enough to confirm a plugged cat. The rear took a week to set the MIL.
I would worry more about the wires, connector or threads being damaged from repetitive use.

I can not see the JCwhitney gauge clearly. I would like to see the readout and the scale. It almost looks like an old vacuum / pressure gauge?