How to gut a 348 factory cat the right way

This is the way I gutted my factory cats for use on my 18,000 mile 348 TS Ferrari. Some may think this is foolish and will want to suggest using aftermarket cat elimination pipes. Some will agree with me as they prefer the OEM look. I'm not doing this to start arguments about that. The reason I did it this way is because I wanted to keep the factory look but have a straight thru exhaust system to the muffler. I have a 1990 348 TS with 18,000 original miles and in almost 100% factory original condition and I want to try and keep it close to original. I know there are some that do not mind modifying their 348's but I want to keep mine close to OEM. I want to go anywhere with my 348 and when people look at my 348 see it as it (more or less) came from the factory. I was lucky to find (locally) a used OEM Ferrari muffler out of a late 348 spider. The owner told me this story: He bought this late 348 spider and wanted a better sounding exhaust. He ordered some cat delete pipes and an aftermarket muffler. I can not remember which muffler he used. He received the cat delete pipes but the muffler was on back order. So he went ahead and installed the converter delete pipes but retained the factory spider muffler. He said it sounded very nice. When the muffler finally arrived he took out the factory muffler and installed the aftermarket muffler. He said it did not sound much different (I would say he maybe said it sounded better but not a lot better. I'm sure he may chime in here and explain that better) but since it was now in and "used" he might as well leave this aftermarket muffler in. Although I have not yet installed these gutted cats and late spider muffler in my 348 I am happy to know that when I do I should have a much nicer sounding exhaust and it will look OEM Ferrari.

My original dilemma started when one of my OEM cats started rattling last year. What to do about this I thought. I happened to see on ebay some of the aftermarket (slightly used) cat delete pipes and I bought them. Once I received them I did not like the idea of having these shiny stainless steel cat elimination pipes with a factory muffler. So I posted here and (luckily) found a 348 owner who had two used cats but the opposite one was bad. So I bought them and now have a set of bad OEM Ferrari 348 cats and a set of good OEM Ferrari cats. This way I can operate on the bad cats since they are bad anyway and still have a pair of good OEM Ferrari cats should I ever need to reinstall them or include them when I sell my 348 one day. We no longer need to do emission testing on pre 95ish cars around here so I no longer need to go for emission testing.

The reason for this long post is that if you remove the brick from a factory 348 Ferrari cat you end up with a hollow catalytic converter case with a baffle in the inlet that undoubtedly messes up the exhaust flow thru this hollow case. I did not want this on my 348. I wanted an OEM looking cat without the baffles and with an exhaust pipe inside so the exhaust will flow the same as if there was just an exhaust pipe in its place. It took me a while to figure out how to do this but I found a way.


Please let me complete all my posts before anyone comments. The only way I know how to do this is make a post for each picture or a couple pictures and some explanation for these pictures.

Rodney Dickman
1990 348 TS

My 348:
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On with the show:

This is a factory original 348 cat. This is what you see when you look in the inlet. Sorry for the blurry picture. I'm too lazy to take another picture. If you take out the brick you still have this damn baffle in the housing. How to get this baffle out without damaging the exterior of the cat?
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First thing is to remove the brick. I had one of my employees hold the cat while I used a piece of rectangular steel I just happened to have laying around. I used a small hand sledge hammer and hammered into the brick. This way no damage was done to the inlet and outlet tubing of the cat. I did not want my exhaust to have any leaks when I was done. Setting the cat on the floor may damage the ends and this would probably cause a leak when installed. It took a while but I managed to break up the brick enough to get it to (more or less) all come out. Once this is done you need to remove the mesh that surrounds the brick. I also used the rectangular piece of steel and hammered it from the outlet towards the inlet until it came out some. I then grabbed that in my work bench vice and slowly pried it out.


So this leaves you with a hollow cat but with the baffles in the inlet.
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How to get that stupid baffle thing out with out damaging the case? I thought about this all last winter. I had an idea and finally started to see if it would work. To get this baffle out you need to cut it into a few pieces or it will not come out. This baffle piece will be too big to get thru the ID of the inlet or outlet pipe. So I cut the baffle up and took it out in three pieces. I used my Makita sazall to make these first cuts. Other sazalls may not work. This one did. To get in far enough I took the foot off the sazall and the boot off. This allowed me to get in farther. They do make some longer blades but I did not try these longer blades. It was somewhat hard to find three places to get the blade in without hitting something and bending the blade. But I did find three locations and started to saw. I only trashed one blade. You do have to be careful or the saw blade will either jam or hit something and bend or break. The tube goes into the housing so you can cut up the weld and still not go thru the case (make a hole visible from the outside of the cat). I used a tape measure to try and see how far I was going. I did each cut a little at a time until I was close to the weld.

While we were doing this I had my employee hold the cat on the workbench and we also laid it on an old towel to keep it from getting damaged from the workbench top while doing the sawing.
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So now I need to cut the ID of the pipe to get these pieces out. This I can do as I have a high speed (21,000 rpm) Milwaukee grinder. I used my home made cut off wheel attachment and an old used cut off wheel that was larger before I started but small enough to get inside the pipe. I made a careful measurement to be just inside the weld and made a few trial cuts to check my position. This was the white line on the high speed grinder. I cut around the ID of the pipe and the three pieces started to become loose. I grabbed them with a long needle nose pliers and broke them off. Success!!! I now have a gutted cat with no baffle on the inlet.
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These are the three pieces of baffle I removed.
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The inlet with the baffle section removed. The small half moon area you see at the 5:00 position is the piece for the O2 sensor.
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So now one needs a length of stainless steel exhaust pipe. As luck would have it I happen to sell exhaust pipe stuff and happen to have some 2 inch OD 409 (.058" wall) stainless steel exhaust pipe on hand. This 2 inch OD pipe is a perfect size to go in the converter. To go in the outlet end you do need to grind the fitting that the thermocouple goes thru some as the 2 inch tube hits it. Once the 2 inch tube is in I will have my welder just tack weld it in place on the outlet end to keep it from coming out. I will reinstall the thermal couple by drilling a hole in the pipe thru the fitting. Although I have dot done it yet I will cut in some fingers for where this 2 inch tube hits the inlet (where I removed the baffle to keep it aligned.
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So now that the baffle is out and when the new 2 inch exhaust pipe is welded in I will have a OEM looking converter with a straight thru exhaust pipe inside and no baffle or empty chamber to change the exhaust flow or exhaust note.


A long post but this is the way I did my cat delete pipes and retained the factory look.

Rodney Dickman
1990 348 TS

Anyone care to put this on some web page so others can reference this in the future?

 

When I install the inner stainless steel tubes I may drill a hole on the underside and have my welder weld the tube to the body and fill the hole. That will keep the inner exhaust tube from vibrating any on the inlet side. This will not be seen from the top.

Rodney

 

Nice post Rod.

Hope you are gonna post some pics of the final product.

 

Nice Rodney.

Now, impress us - put it back togeter

 

This is an interesting project, but I have to ask if it doesn't look more like a "make work" project than alternatives. This looks like an awful lot of effort to essentially have straight pipes that still have flow restriction, but look stock. For one thing, the O2 sensors still mount right in the exhaust flow unlike the 355 version. You should probably relocate those things out fo teh inlet tube. The tubing is still narrow, IMO. I don't know. No disrespect to you or your effort, but I cannot see duplicating this project for myself.

If you really want to increase power and flow, junk everything past the headers and replace with wider diameter stuff. I would guess that my new cat system (aka the gothmuff) flows better than stock even with cats deleted.

 

I am looking for a better sound but still look OEM Ferrari. Period.

Rodney