I always look for innovative ways to boost my car’s performance. When I learned drilling holes could contribute to enhancing performance, I was all set to puncture the cat on my car.
However, I changed my mind after doing some research. Several factors led me to conclude that the holes would do more harm than good.
It is not a good idea to drill weep holes in the catalytic converter because they will allow harmful gas to leak and pollute the environment. The gas can also infiltrate the vehicle’s interior and even poison the driver.
Moreover, your cat might fail emissions tests if it has holes. Overall, it appears to be a bad idea, doesn’t it?
In the article, I will discuss the issues of having holes in your converter in greater detail.
Without further ado, let’s get started!

What Is the Role of Catalytic Converters?
Before explaining why you should avoid making weep holes, I need to point out how important catalytic converters are.
As you may already know, vehicles produce a large amount of toxic gas. The gas won’t stay in the vehicle forever.
It eventually makes its way into the environment. Just imagine the devastating effects on the environment if thousands of vehicles release harmful gasses every day.
Thankfully, a device called the catalytic converter does not let this happen. It ensures the gas does not pose a severe threat to the environment prior to release.
This way, people can drive vehicles without adversely affecting the environment.
What Happens If You Have a Hole in Your Catalytic Converter?
As soon as you make that one single hole in the cat, there is no turning around. You will immediately defeat the primary purpose of the device mentioned above.
So what really happens then? Here is a more detailed explanation of that.
1. Affects the Environment
Even a single hole compromises the converter’s performance. It means the device will no longer convert hazardous gasses into harmless ones as effectively as it used to.
Currently, most vehicles have cats, as required by emission laws. Despite this, pollution rates continue to go up. So just imagine how dangerous the pollution levels will be if your car does not have a proper functioning converter.
2. Causes Health Problems
Many folks are ignorant of the fact that the holes pose a hazard to the vehicle’s driver and passengers too.
These holes allow toxic gas to pass through and reach the vehicle’s interior. You keep breathing in the gas without realizing it since there is no smell to it.
It is common for people to vomit, become dizzy, and lose consciousness after being exposed to the gas. When left unaddressed for too long, it can even lead to brain and heart damage.
What Is the Purpose of Drilling Holes in Catalytic Converters?
Okay, so it is clear that a cat’s weep holes have harmful effects, especially on the environment. Nonetheless, a lot of motorheads drill them anyway for usually three reasons. Let’s talk about them.
1. Better Performance
As for the first reason, it is pretty obvious. Weep holes can improve the performance of your vehicle. But how? Let me clarify.
The biggest secret of a high-performance car is a combustion chamber filled with an abundance of oxygen.
When the oxygen level rises, the car can generate more combustion. Upon achieving a certain amount of combustion, your vehicle will get a horsepower boost.
Unfortunately, a catalytic converter prevents adequate oxygen entry. Thus, if you cut holes in the device, oxygen will enter the combustion chamber more efficiently and enhance the car’s performance.
2. Reduced Clogging
The clogging of a catalytic converter can happen in a number of ways. One of the main causes is definitely the excess fuel roaming in the exhaust system. Coolant leaks and oil entering the exhaust can also clog converters.
If you puncture a few holes in the cat, the trapped substances will spill out and prevent clogging.
3. Smooth Engine Operation
When the pollutants and gasses can’t exit the converter, your vehicle’s engine won’t run properly. Many problems can arise, including the car jerking forward, poor mileage, and even the engine not starting.
Cutting holes will allow the unwanted substances to escape and keep the catalytic converter clean. As a result, the engine will run smoothly.
Method of Drilling a Hole in Catalytic Converter
In case you feel that the above benefits are absolutely necessary for your car and do not mind the risks, go ahead and make the holes. However, please note that this is entirely at your own risk.
With that in mind, I will outline an easy and simple method below for drilling holes in cats.
Tools You Need
STEP- 1: Jack Up the Car
Ensure that your car is parked in a safe area and that the hand brake is on. Jack up the vehicle so that you can locate the catalytic converter easily.
STEP- 2: Find the Converter
Check the area behind the exhaust. The converter should be mounted around the muffler. It resembles a cylinder-shaped casing consisting of two pipes.
STEP- 3: Disconnecting the Converter
Cats are attached in two ways: welded and clamped. When it comes to the clamped one, simply remove the clamps.
However, a welded cat requires cutting both pipes with a saw to detach the device.
STEP- 4: Creating Holes
Now you should position the chisel on the pipe at the end of the converter and hammer it. After holes are drilled on one end, repeat the process at the opposite end.
Also Read: Is it a problem if the heat shield on the catalytic converter falls off?
Can I Drive with a Hole in My Catalytic Converter?
You can certainly drive your vehicle with a hole in your catalytic converter. However, I do not suggest it due to the toxic gas that is likely to be present inside.
If you breathe it in for some time, you may experience side effects such as dizziness and vomiting.
The more you inhale the gas, the worse the effects will be on your health. Hence, I recommend replacing the cat and driving the car afterwards.
To Sum Up
Besides slightly improving performance, drilling weep holes in your converter do not offer many advantages. There are actually other safe methods of enhancing the performance, such as muffler deletion and tuning.
For a tiny gain in performance, I would not recommend endangering your health and the environment by puncturing your catalytic converter.
Interested in reading more articles about cats? Have a look at this one to find out whether test pipes replace catalytic converters.