This is transferred from 87-96 Truck Forum so I can respond with my experience at drilling holes in the muffler. First the original posts:

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Original Message
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"Holes in a Muffler?"
Posted by kiksomepoo on 12-Sep-01 at 06:08 PM

A friend was telling me that you can put holes in your muffler and it will make it louder and not do anything, is this true? i just dont want to screw anything up. I am doing this just for kicks though cuz i am getting dual exaust in a week or 2. Thanks


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"RE: Holes in a Muffler?"
Posted by kiksomepoo on 14-Sep-01 at 10:26 PM

Well, thanks for all the info, but i tried it anyways. It suprisingly works very well if anyone is interested in doing this its kinda fun and sounds pretty good, but you could never pass inspection. I drilled about 25 3/4in holes in the back of the muffler (coming from the engine) then i made a 2" round hole in the bottom, of the back part of the muffler. The small ones make the sounds when you are idling or barley gassing it. The big big hole pushes it out fast and sounds nice when accelerating quickly.

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"RE: Holes in a Muffler?"
Posted by TallPaul on 02-Nov-01 at 08:02 AM

Folks, I just tried this last night, but since this is supposed to be in the Exhaust forum, I will copy the posts over to the Exhaust forum and then will post my experience there. Otherwise, if I respond here, Ken is going to lock the thread.

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"RE: Holes in a Muffler?"
Posted by jim henderson on 12-Sep-01 at 06:38 PM

Since you are going to dump the mufflers in two weeks I guess it is OK to punch holes in them as far as destroying the muffler.
One thing to watch for, especially with older engines, you may be carbon monoxide leakage into the passenger compartment, really bad for your health, so I wouldn't do this unless you don't do a lot of idling or get stuck in snow or traffic.

The noise won't be much unless you make a big hole.

More fun and maybe easier is to just chop off the pipe from the muffler back to where ever it goes. Not the engine side, unless you want it "Give me a ticket" loud. Cutting the pipe at the exit side of the muffler will usually be plenty loud enough for most people. Not safer though. Be sure to wire up the muffler so it has some support. There is also an off chance of too much heat damaging the under side of your truck if the pipe is close to things. Note that dual exhaust on a truck that originally had single, may not meet smog check requirements where you live. A short pipe or holes in the muffler almost surely won't pass.

I don't recommend this but if you are going to do it, you might as well do it right. If you get carbon monoxide poisoning or a ticket don't blame me.

Jim Henderson


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"RE: Holes in a Muffler?"
Posted by TallPaul on 13-Sep-01 at 08:33 AM

If you cut off the pipe behind the muffler, see if a curved section of the old tailpipe can be hooked up to make a side exit in front of the wheel.
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"RE: Holes in a Muffler?"
Posted by kiksomepoo on 14-Sep-01, 10:26 PM

Well, thanks for all the info, but i tried it anyways. It suprisingly works very well if anyone is interested in doing this its kinda fun and sounds pretty good, but you could never pass inspection. I drilled about 25 3/4in holes in the back of the muffler (coming from the engine) then i made a 2" round hole in the bottom, of the back part of the muffler. The small ones make the sounds when you are idling or barley gassing it. The big big hole pushes it out fast and sounds nice when accelerating quickly.

 

I wasn't going to try this because of the CO concerns and that the family occasionally rides with me, but then I reasoned that the back of the muffler is well under the bed so that any buildup is somewhat separated from the cab and I don't sit idling in one spot (still caution is warranted), so I had at it last night. Not remembering the above posts, I just went at it with a 5/16" drill. Three holes, not much change in sound. So I gave it 10 holes in the backing plate and quit for the night. This am noted that it is somewhat louder at idle and cruising, but not too loud. Under acceleration it is also louder. The sound is iffy though--really sounds like a muffler that is going south. Maybe I should try the 2" hole too, but at least with the 5/16' holes I reasoned that if I didn't like it I could plug them with short, fat screws. How to cut the 2" hole though. All I have is a hole saw that probably is meant for wood. Also, if I take it to the repair shop, I owe it to the mechanic to plug the holes so he dosen't get poisoned running it with the tailpipe hose out his door.

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The holes in the muffler are not a good idea. Exhaust gasses will flow upwards and forewards while moving and if you have a rear sliding window tha is open..... Have you ever carried leaves or grass in you truck bed? thay always move to the front of the box when moving and fly around the back window and if it is open they will come on inside. Yaers ago i modified car and motorcycle muffler by ramming a bar down the muffler ports to punch a hole in the baffles inside. Care has to be use when doing this mod as to not go right through the opposite end of the muffler and ruining it. The police also take a dim view to holes in the outsid of the muffler and the heat escaping through these hole will burn the muffler out faster too. My$.02 worth.

 

I hear you StevieRay and your point is well taken, which is why as soon as I noticed my wife's Aerostar's muffler going I had it replaced within a few days. But in the pickup truck I don't have a sliding back window. Wife and kids rarely ride in the pickup. But I probably have spent 15 years of my life driving a pickup with no tailpipe, just the muffler outlet. This is not much different. I know of no law that prevents me from modifying my muffler so long as it dosen't violate noise limits. If the holes make the muffler burns out faster, so be it--it helps my cause, which is to ultimately try a straight pipe and if that dosen't do it, a Flowmaster muffler.

 

 

this is just stupid !
just get a cat back and do it right !
just my .02 $

 

>this is just stupid !
>just get a cat back and do it right !
>just my .02 $

Why should I spend $200 to $300 on a cat-back system when for free I got the sound I want. I am happy with it and have avoided paying a certified mechanic to put some fancy piping under my truck.