OKJefe

Not being very tool savy I started my project today and got the outer hole drilled on the drivers side muffler and almost made it through the outside of the muffler first layer on the passenger side when I broke my drill bit. :

My buddy had showed up while I was in the middle of the mod and when I crawled out from under the car cussing the broken drill bit he says to me, "Well there's your problem, you're using a wood bit on metal."

Ask me how sheepish I feel and on top of that lucky for me the hardware store was closed for the day. Cue violin music here. So tomorrow I get to go get a new metal cutting bit and finish up my mod.

Wish me luck.

megaweapon

While you're there don't forget to pick up the knock out plugs for the hole. I went through three of the Milwaukee hole saws for two 7/8" holes.

cclive

Get a Milwaukie hole saw not a drill bit...mine went through and made all the holes in just a couple of minutes per muffler. A drill bit will grab as it gets through...causing possible breakage (as you know). The hole saw is only $12 or so at Home Depot.
They make hole saws for wood too, so be sure to get the white ones that are for metal too. The wood ones are cheaper and therefore tempting.

OKJefe

Thanks for the heads up ya'll. Got everyting squared away today and it's amazing how easy it was with the right tools. I'm liking the subtle change.

Mad*Max

I used the same one for all four holes (I didn't do six like others), it says "ice hardened" on it...I actually ended up doing a 1 1/8" hole (x2) on both sides but only went to the first layer of the inner pipe - this has given me enough sound and has certainly woken up the exhaust. It is such a difference when you start it up.

I am hearing a slight drone on the highway when the engine is under load, I wonder if this is the same for others?

loudvolvo

pull out the fiberglas while your at it to....gives ya a lil more sound.

Ozarkwoods

I went with the 7/8 hole through the cans and both walls of the pipe inside. Then closed it up with the 1/2 plugs with red RTV. The idle sound had changed to a nice deeper rumble...I have not had a chance to get it out on the road yet under load.

BWF07

O, tomorrow I will be doing the muffler mod to my '07 coupe. I have everything I hope I will need. I have a 1 &1/2"as well as a 1' Milwaukee hole saw. I have two of the electrical knockout plugs that were mention in an earlier post and I also have the sheet metal and screws is the plugs don't seem to be the trick.

I have looked at the different threads and although everyone, or at least most everyone is doing the outer hole in the muffler in an 1 &1/2" and the inner pie in 1" it sure looks bigger then the two hole saws I have. I guess it is just that the pictures are closeups.

vig1116

if you are going to use the plugs, why use a bigger hole saw for the outer muffler? I used a 7/8 hole saw through the outer and inner 2 holes. Then i plugged the outer hole with whatever size fit the 7/8 hole (1" plug maybe? i forgot) i then put heat silicone around the hole. it's perfect till i get corsas...

BWF07

I actually bought two 1&1/2" plugs and 2 -1" plugs, it appears believe it or not that the 1" plug will fit the 1&1/2" hole. At least when I compared it to the hole saw. If they don't work, I do have the sheet metal ready.

With the 7/8" hole were you able to remove any of the fiberglas?

vig1116

i wasn't able to remove any fiberglass. I'm not sure it was because of the size of the hole, i think i was too far forward where i drilled...

BWF07

I am going to try and get some out. I guess a wire with a hook to snag it and pull it to the hole. and I will have on long sleeves and gloves.

Mad*Max

you might want to drive it and listen to it before you remove it

vig1116

look at the pics of the cutout muffler. If you drill where i drilled even with a hook you cant get to it because of a wall. You have to drill beyond the wall..

Markallamerican

On my 07 m6 I drilled a second hole, toward the front of the car a few inches, This gets you into the second chamber of the muffler where the fiberglass is. See picture on page 29. I also Drilled a 1 inch hole in the inside pipe in that chamber.

BWF07

Got the mod done and it does have a nice mellow sound. I happen to have the A6 so it has a drone in the lower gears, but not bad at all, but in 6th the drone is almost unnoticeable.

I remember seeing that the fiberglass was in the center and there is no way to get to it from the holes drilled at the rear of the muffler. I suppose I could drill a hole in the center of the muffler to get at it, but I think I will stick to this for now.

loudvolvo

i went back later and drilled a hole in the middle to get the fiberglass out. just used a coat hanger and a long pair of needle nose pliers to get it all out. definetly made a diffference in sound. guess i just got bored with the regular muffler mod.

cclive

I know it's not easy to verbally explain a sound, but can you tell me how the sound changed when the fiberglass was removed...what was the change in the character ofthe sound?

ptroxx

anyone have info on the NNP muffler mod......something with pics ?

BWF07

Here is the NPP mod. It is a lot more involved then the stock muffler mod.

http://forums.corvetteforum.com/1583018181-post563.html