Glasspack Mufflers 101: Sound, Power Gain & Are They Legal?

A glasspack muffler is a type of muffler that is designed to increase exhaust sound and also bring some more horsepower out of the engine.

The sound is similar to straight pipe, but better- it’s more refined and aggressive.

I have installed some glasspack cherry bombs on my cars in the past. There were times when I was in high school and didn’t have a penny. I found one glasspack cherry bomb exhaust right out of the junkyard and paid 20$ for it. 

It was worth every penny. My Camaro sounded mean and also ran faster. The sound reminded me of the time when I was running open headers, but better.

In this article, I am going to discuss details of glasspack mufflers:

  • Horsepower gain
  • Sound improvement
  • Comparison with other mods like muffler delete and straight pipes 
  • Legality 
  • Cost 

It’s going to be an informative one. So relax, get some coffee and enjoy.

What’s Glasspack Muffler & What Does It Do?

Glasspack muffler is a muffler that’s designed solely with performance and sound in mind.

It is a simple straight-through muffler tube with some sound suppression design within the walls. It’s like a straight pipe, but better sounding.

The design of a glasspack muffler is fairly simple. There are two tubes on it – one is smaller with holes and the other one is bigger. The bigger one is on the outside of the muffler. I

n between the two pipes, there is fiberglass. Because of the fiberglass material they are known as glasspacks. 

the internal of performance muffler

Glasspack muffler is a straight through tube with fiberglass packing inside.


Their role is to give you a good sound and make more power. Since straight pipes were making a lot of sound. 

Something more mature and better solution needed to be made – and this was it. A muffler with performance and loud sound in mind. 

Glasspacks originated from the muscle era in 1968. They were produced by a company named Cherry Bomb, and that is the name that most people connect to glasspack mufflers.

Does Glasspack Mufflers Add Horsepower?

Glasspack mufflers will improve your horsepower rating of about 20 horsepower compared to stock. They improve horsepower because they reduce backpressure and are lighter compared to stock ones. 

If you don’t know, reducing backpressure is basically reducing the amount of pressure coming from your exhaust pipes. The lesser the pressure, the quicker exhaust gases leave your car.

Which means more room is available in the combustion chamber for oxygen to enter and create bigger combustion and horsepower. 

Glasspack mufflers are literally straight-through muffler tubes. They are significantly less restrictive than stock mufflers. Thus, reducing backpressure significantly.

More info about backpressure here. Is Back Pressure Good For Turbo? (No, it’s Not) 

Glasspack mufflers

Glasspack mufflers reduce backpressure significantly and is lighter than stock. Thus, increasing horsepower.

How Loud Are Glasspack Mufflers?

Glasspack mufflers are loud. They are loud as straight pipes, but the sound is more mature. The car isn’t screaming like with straight pipes but makes a more rumbly and pleasant noise. 

This is made possible by the fiberglass and sound enhancements design they have in glasspack mufflers. 

Here is a good video on comparing the straight pipe exhaust and glasspack exhaust systems.


As you can see in the video. The glass pack makes a sound similar to the straight pipe when you apply the gas. But the sound is more nimble and pleasant. It’s not as sharp and obnoxious as the straight pipes.

A lot of people ask about the comparisons of glasspack mufflers with other mods like muffler delete and straight piping.

So below are my thoughts on them. I personally have tried them all, so my opinion should have some weight (right?).

Are Glasspack Mufflers Louder Than Regular Mufflers?

Glasspack mufflers are a lot louder than regular mufflers. There is no comparison between the two. 

Regular mufflers are made to be environmentally friendly and also aid the fuel economy. Glasspack mufflers on the other hand are made for performance and sound. 

Moving directly from regular stock mufflers to glasspacks will probably give you a shock. So hear the comparison videos on YouTube first before making any decisions.

Are Glasspack Mufflers Louder Than Straight Piping?

Glasspack exhausts are not louder than straight pipes. Straight piping completely removes any sound suppressing mechanism from the car.

This means your car sound is extremely loud and natural.

Glasspack mufflers, although loud – still have some sound suppression from the fiberglass within its walls. It’s pretty loud but not as loud as straight piping. 

The only benefit of straight piping over a glasspack muffler is that it’s much cheaper and you can actually DIY. All you need are some replacement pipes, saw and welder.

If you care about the actual sound, then a glasspack muffler is the go to. There’s actually R&D that goes into creating the glasspacks – R&D that makes your car sound loud but still pleasant. 

Image of straight pipe exhaust

Straight piping completely remove CAT and muffler. It’s louder than glasspack mufflers.

Are Glasspack Mufflers Louder Than Muffler Delete?

Glass packs are not louder than muffler delete. Similar to straight piping, muffler delete completely removes the muffler from exhaust. This means the sound suppression is reduced.

In comparison, glass pack mufflers still have some sound suppression through its fiberglass packing – making it loud but not as loud as muffler delete. 

If you are wondering, straight piping is louder than muffler delete because straight piping removes both catalytic converter (cat) and muffler.

Although not a sound suppressing device, a CAT is extremely restrictive and still plays a role in quieting down a car.

Are Glasspack Mufflers Legal?

Glasspack mufflers are not legal in every state. Depending on where you live. For example, if you live in California, you will have a lot of trouble while running these mods. 

You will gain the attention of the cops and the chance to get fined is pretty big. The same is true for every big city in the USA. If you are living in big cities, there are high chances that the glasspack is illegal.

On the other hand, if you live in the countryside where there isn’t much traffic. And in some states, where laws are looser. You will probably get away with it.

Most states do not have a law with glasspack in general. Instead, they have a law that dictates how loud a car can be. Check out your local laws before deciding to purchase a glasspack.

Glasspack mufflers are commonly used in track – during races where every little horsepower counts.

Glasspack Mufflers Get Louder Over Time – True?

Glasspack mufflers get louder over time because the fiberglass starts to burn at 1000 degrees Fahrenheit.

This means the sound suppression capabilities for the glasspack mufflers are reduced over time.

This usually happens after about two weeks to a month of driving (depending on how often and how aggressive you drive. 

There’s usually no fix to this. Just set your expectations right. Before you buy the glasspack muffler from a shop, know that it will get even louder in one month.

I write more about this topic over here Do Exhausts Get Louder Over Time?

How Much Do Glasspack Mufflers Cost?

Glasspack mufflers are pretty cheap and affordable. Mostly because of their simplicity. They don’t pack technology and the manufacturing process is very simple.

Two pipes with fiberglass between them. You cannot get simpler than that to be honest.

Prices of the exhaust on eBay or a similar site are ranging from 50$ up to 90$ (without installation). Installation could cost another $50, depending on your relationship with the mechanic.

Personally, I would skip on the installation cost and try them myself. It’s not that difficult and you can find plenty of tutorials from YouTube.

Personally, I would go with the original Cherry Bomb version. Although they are offered by many manufacturers.

But these I think will give you the right 60’s vibe, since they are all painted red and bring back the old memories of the hot-rodding days.


Glasspack mufflers are pretty loud and cheap! They are great for enthusiasts who absolutely love loud sound and want a little more horsepower. 

Take note glasspack mufflers are illegal in most states and you should install them only on track cars. Don’t bother installing them on your daily. I guarantee you will get bored of the loud noise after a week and regret it. 

Ifandi L.

Ifandi L.

Passionate about everything mechanical. Ifandi has been involved with motorcycles and cars since the old days - in his family's auto parts shop. Want to keep in touch? Scream "STRAIGHT PIPEEEEE" at the top of your lungs and Ifandi will show up.


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