These are the most frequently asked questions (FAQs) we get about the Porter mufflers...

Are your muffler inlet/outlet dimensions listed as inner diameter or outer diameter?

Porter Muffler Inlet/Outlet sizes are “Inner Diameter” (I.D.) dimensions. If you have a 2.25” O.D. pipe our Porter Mufflers with the 2.25” I.D. will slip directly over the pipe.

Are there specific inlet and outlet ends on a Porter Muffler?

The core of the Porter Mufflers is the same in either direction so there is no specific inlet or outlet side.

Are Porter Mufflers available in longer or shorter lengths?

Due to increasing volume in our manufacturing we have stopped making custom-length mufflers. With our unique core we are limited to 20” as our maximum length for longevity and found no worthwhile decrease in sound volume with a longer muffler. The “Shorty” muffler we offer is about the minimum length you would want to achieve a good balance in sound absorption and sound quality.

My exhaust system gets hot enough to heat-up the interior of my car, do your mufflers radiate a lot of heat?

The heat build-up that occurs with a lot of "turbo" and chambered mufflers is due to the the hot exhaust gases getting trapped inside as they go through the various mazes within those mufflers. Porter Mufflers are a straight-through design so heat goes though our muffler without slowing down and much less heat gets radiated into the cabin of your vehicle.

Is there a preferred position in the exhaust system that you recommend?

Porters will sound best when they are located near the center of the system or with at least 3’ of exhaust pipe before them and 2’ of tailpipe behind them. This will achieve the best sound quality and maximize performance.

I have an early Camaro with the transverse-mounted muffler between the axle and gas tank, will your mufflers fit in the same location if they are stacked?

Yes, this is a popular installation option with the 1st and 2nd Generation Camaros, Firebirds, Novas, and Venturas. When stacked together the standard-length Porters match the original inlet and outlet positions almost perfectly and your exhaust professional can make mounts to position them in this location.

I’ve had the insulation in glasspacks burn-up in a matter of months, does the stainless-steel packing in a Porter Muffler ever wear-out or burn-up?

The unique stainless-steel wool insulation we use is designed for high-temperature applications and should last the life of the car. It will compress against the outer casing as it "breaks-in" but will never burn-up or blow-out like other insulators.

I noticed the core of the 3” Porter Muffler is smaller than the inlet, won’t that cause restriction?

20140710_093608 When looking through the ends of one of our 2.50" or 3.00" mufflers you are seeing the core support plate and its opening is just under 2.50” in diameter. In a normally aspirated car or truck exhaust gases flow in pulses, which are very elastic. The pulses will push through that core support opening at a slightly higher velocity, then slow in the insulation chamber, then speed-up through the other end as it exits. With no walls or chambers in the flow-path the exhaust system doesn't see much back-pressure even with these support plates.

Does the internal spring core ever rust-out or break?

In the history of the company we are not aware of any cores ever coming apart and we purposely limit the maximum length to prevent damage from excessive vibration. The cores are made from an engineered, 1/8” thick, 1/8” gapped, high-tensile steel spring that is significantly thicker and stronger than the sheet-metal core used in other mufflers.

What does a Porter Muffler Sound like and what gives Porter Mufflers that unique sound?

The combination of the spring core, dense stainless-steel wool insulation, and thick casing all contribute to the famous Porter sound. The spring core’s surfaces reflect higher frequency sound waves causing both a cancellation effect and reflection into the densely-packed insulation. Everyone’s perception is subjective but the best description we’ve heard from customers is, “A unique, deep, rich, tone that is crisp and free of the “tinny” sounds and echoes you hear with other performance mufflers.” No matter how mild or wild your engine is a Porter Muffler will give it a great sound and keep those sounds on the outside, not in the interior.

I just installed a pair of Porter Mufflers but my exhaust is pretty quiet and making a puffing sound, is that going to change?

Being a hand-made product there will always be a little variation in the packing of the insulation. Sometimes our mufflers get a little over-packed and the "puffing" sound is from the insulation pushing against the core spring, not allowing it to redirect the sound waves. This will go away with about 1,000-1,500 miles worth of use as sound pressure compresses the insulation against the outer casing and you will get the full Porter Muffler sound effects!

I was looking for a local shop that carried Porter Mufflers but none did, are you opening more dealers?

We are always eager to bring new dealers into the Porter Mufflers family where we don’t have a local presence so if you know of a local shop that does high-quality work and has a good reputation please let us know about them! Also, check out our special offer in the news section!

What size exhaust tubing would you recommend for a car with a mild Chevy 350 engine and how will it affect the sound?

Short version - the larger the exhaust tubing a system uses the louder the system will be and smaller tubing tends to quiet the sound. Lean towards a conservative tubing size when designing a street exhaust system, you'll enjoy driving your car more and still get a terrific sound! More conservative exhaust pipe sizes will also make an exhaust system easier to make, install, and offers more suspension and ground clearance. The exhaust flow from a 500hp engine will go through a 2.00" system as well as it would a 3.00" system with little change in power. The velocity of the exhaust flow will be the only difference and that will effect how well a muffler works. Talk with a local, trusted exhaust shop and be realistic about the kind of use your ride will see. Their experience will help you design the right system for you! The one universal recommendation we do give is for the iconic flat-head. We recommend a dual 1.75" or 2.00” (size depending on power level) system and our ‘shorty’ mufflers. This is the finest sounding flat-head exhaust set-up around!

How does a Porter Muffler sound on a Harley Davidson?

This is a question that has come up for years and we always had to say, "We don't know" as we had never heard one installed on a bike. Well, now we have and you can too! One of our local customers had a pair of our 1.75" standard mufflers installed on his Electra-Glide. The signature Harley rumble is still there and the harsh edges are taken off so it is slightly more mellow but it still has that deep, throaty sound. Cruising is a lot more comfortable with this set-up and we are looking at another installation coming soon!

Do you have Porter Mufflers in stock, and how quickly can you ship them?

Porter Mufflers maintains a large stock of all of our mufflers, ready to go. Orders for shipping within the United States ship same day on every order placed before 2:00pm central standard time!