Hollowing Out a Catalytic Converter – Full Guide


Hollowing out a catalytic converter will result in a maximum power increase of 5 HP. The hollowing out a catalytic converter also creates resonance issues. The most common symptom is popping or hesitation. Also, it can backfire at nearly 3000-4000 RPM.

Let’s discuss a bit more about hollowing out a catalytic converter.

Some Queries Regarding Hollowing Out a Catalytic Converter

Here, we have some basic queries for hollowing out a catalytic converter in upcoming questions.

What will happen if you remove Catalytic Converter?

The heat or warm air will cause metal to expand, making removal more difficult. After removing the converter, catalyst will resemble honeycomb inside. It is solid and difficult to remove the same, but you still can break it with crowbar as chisel plus a hammer.

What Happens When a Catalytic Converter is bypassed?

Tampering with or removing still-functioning catalytic converters is illegal and can result in thousands of dollars in fines. Toxic fumes are released into the atmosphere. Removing it will result in more harmful pollutants being released into the atmosphere. It not only harms the environment, but it may also harm you.

Do I need to replace my catalytic converter if removed?

In addition to potentially damaging other components, removing the catalytic converter could harm oxygen sensors connected to the converter. As a result, the vehicle will fail its emissions test. Engine light check may come on as well.

Three Catalytic Converter Repair Suggestions / Tips

A troubleshooting job for catalytic converter may be a challenging one. Still, with a bit of knowledge about cars and lots of patience, you should now be capable of successfully fixing it. The understanding of catalytic converter is key. You can get an idea of how to repair your car’s catalytic converter by reading these tips.

Here are some suggestions to help you repair your car’s catalytic converter.

Examine Warranty Cards

You should check the warranty card before you work on catalytic converter. You should return the converter to the manufacturer for repairs or possible replacement if it malfunctions within the warranty period. Do not tamper with catalytic converter during the warranty period, as this will void the warranty. However, if the converter malfunctions after the warranty period have expired, you are welcome to repair it yourself.

Check for Clogging in Catalytic Converter

The converter should be thoroughly inspected before any repairs are made. Take the converter off your vehicle to determine if there is any problem. You should do this by lifting your car with a jack and jack stands or using a ramp and looking for a catalytic converter.

Loosen the Bolts

Normally, the converter sits between the engine and the exhaust system. Before removing the converter, loosen the bolts holding it in place. Spray lubricant on any bolts that won’t budge and let them sit for about an hour before you attempt to loosen them again. With gloved hands, remove the converter after the bolts have been removed.

Inspect the Converter

Once the converter has been removed from the vehicle, inspect it for damage and defects. Catalytic converters that are plugged malfunction, so check for clogs in the pores of the converter. Clean the pores with auto cleaners if they are clogged. Using the tip of a small screwdriver is an effective way to remove stubborn dirt from the pores.

Check the Air Passages

Check the air passages of the converter after inspecting the pores for soot. Clean them thoroughly if they contain soot.

Examine the Converter for Damages

Despite the converter’s external hardness and durability, its interior comprises thin-walled, lighter materials. Already, the insides of converters are fragile and prone to damage. The insulating mat holding the catalyst is easily damaged by bouncing converters. Mat breakage may accumulate in smaller passageways of the converter, constricting them. Replacing the insulation mat of the converter if it has holes or breaks is recommended. The broken areas should not be bonded back together. Once the mat is damaged along several lines, it no longer protects the converter effectively.

Tools Required for Hollowing Out a Catalytic Converter

The tools required for hollowing out a catalytic converter are given below

  1. Drill
  2. A long spade bit
  3. A hole saw
  4. A hammer
  5. A chisel

If hollowing out a catalytic converter is necessary for you and you are ready to do so, there is some method. So, be careful and do anything you want with utmost care.

Step No.1: First Remove Catalytic Converter

Start by hollowing out a catalytic converter beneath the vehicle. It will surely be lying near exhaust and frequently attached to the same, and you might be perfectly capable of reaching touch the same, but surely, you will never be capable of completely removing the same without even lifting your car. You better should get floor jacks (two of them) and place them beneath your car to fully support the wheels. Lift the car, secure it with jack stands, and crawl underneath. Then, with your wrench, try to loosen all the bolts that hold the cat properly and smoothly pull it away from the exhaust because you extract all bolts.

Step No. 2: Make a Hole in it

You should be hollowing catalytic converter out at this point. Bring some parts to workbench and place them in your vice (face it upwards) to reveal the honeycombed core. Put on respirator masks. Insert the crowbar at the top of converter. Tap bar gently with your hammer to see core beginning to crumble. With a few strokes, you will now be capable of reducing honeycomb to a fine powder. Empty now catalytic converter and turn it around. Remove core from another side the same way. Continue the process until core has vanished completely. This comes secondary for hollowing out a catalytic converter.

Step 3: Replacing / Reinstalling  of Catalytic Converter

Slide the converter back onto exhaust. Then, push the same into place to reinstall. Take out your bolts now and properly screw them in place by hand before tightening them with the wrench. Get yourself out if you are still beneath the car. Now, remove all floor jacks once cat is in place. You would be left now with large amounts of platinum-containing powder, which you can recycle or sell for cash only if necessary. These catalytic converters will undoubtedly operate now without core, but they will not perform the function for which it was originally designed.


So, we have discussed here about hollowing out a catalytic converter(s) and have provided tips plus tools required.  It is not only hard but also illegal to hollow out a catalytic converter in most states. There is no good reason if you hollow out a catalytic converter, and you may suffer legal consequences. In most cases, you should leave catalytic converter alone and seek another solution for your issue. You can, however, hollow out your catalytic converter if you are well trained and determined to do so. You should be aware that you may break your own car, or can cause it to run poorly, and that some mechanics will not assist you if your catalytic converter fails. A professional will not do the work for you, as it is a process that must be done by you.


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