426 Hemi

Just got back in from the shop---pretty pleased.

I know this has been covered before, but I just had to post. And---and thanks to all who posted about this in the past.

The "H" pipe came off really easily---slipped right off. The driver side muffler twisted out not too bad (sway bar swung down). But the passenger side was no fun. Finally had to take one CF member's advice and loosen the cradle ----dropping it down for that bit of clearance.

I used a thin cut off wheel to cut the hole in the mufflers. Pretty easy. Pulled the "pillow", "mega cat hairball" or whatever that thing is.

Found a piece of pipe who's ID was the same as the OD of the perforated section. I sliced it lengthwise, pried it open and pushed it over the perforated piece. Used a large pair of channel locks close it around the pipe then MIG'ed the seam back together.

All that was left was to MIG the square panel back on and spray it with some hi-temp paint.

Mufflers went back on easily----some WD-40 helping out with the hanger rubber out back.

Then it was time to start it. Had to take a pee real bad---but no, gotta hear them pipes. Guy thing.

Man what a difference. Alot more throaty. Nice tone at idle. Took it out on the road too. More noise while getting on it. Sounds good. More popping when backing off but that's ok.

Didn't really notice much difference in quite mode---still no drone at highway speeds.

Well anyhow that's my story. Nice mod. Now to go pee......

tjwong

Did you leave the bags of mineral wool strands out? And did the guy use a plasma cutter on the cans? If not he made some very nice cuts. I use a plasma cutter to do the same. But I stuff the mineral wool back into the cans, not sure if it even does anything with the internal pipe welded up.

50 4Ever

Congrats, I love the sound of mine (same mod).

426 Hemi

Yeah you know I was about to grab the plasma cutter but instead I used the cutoff wheel. Looks like this:



Worked nice but the plasma would have done a great job too.

I did leave mine out but I'm sure it would have been fine to put back in. Might dampen any "tinnyness" of the cans or maybe dampen some resonance.

Same here---a definite "must do" IMHO. And I think it only took like 3 hours to do.

dvandentop

cool free mod

gotjuice?

Nice write up. I would like to do mine, If I cannot find the Fussion at a reasonalbe price.

Mark Ducati

1) How many ponies do you think this will add?

2) How much more additional sound will you get in conjuction with a M2W mod.

3) How much does this mod run at a local muffler shop.

4) Anybody have EXACT dimension of where to cut and reweld?

5) Are you also welding a solid pipe beneath the peforated top piece you can see.

6) Anybody around the Atlanta Area have this done locally?

Thanks,
Mark

Z06high

Great pictures and info thanks for posting. Do you remember the ID size of the sealing pipe? Where did you find it? I'd like to have this before I start the project to save time. Thanks!

EXCELR8

Congrats, did the same mod. With a cam and headers the sound is insane. Mild to Wild programed to the visor still gives me the quieter option when wanted.

tjwong

It maybe worth 5hp tops. There is a considerable increase in noise level when the valves are open, with them closed the noise level is unchanged. The perforated portion is covered up with a 3" section of tubing that is cut in half. It isn't a perfect weld because one can't get to the backside of the perforated portion, but what is left won't matter.

If you find a muffler shop to do it, make sure that they are meticulous in their work, you don't want your rear muffs to look like Dr Frankenstein work on them

426 Hemi

Like TJ said maybe 5 hp or so. Basically the mod didn't increase the flow or pipe size---just eliminated exposure to a chamber. However by eliminating the perforations it might have provided a less "turbulent" path.


I think someone said before it's like 30% to 40% louder. I'd have to agree.


I did mine myself but it would probably cost (just a guess) 3 or 4 hours of labor worth. BTW I've also heard where some shops don't even pull the muffler off the car. They just disconnect it and hang it down to do the work i.e. saving time and cost.



Hope this helps. BTW it doesn't matter if the hole is made on the side of the muffler to the outside or inside of the car. Did mine to the inside.




The pipe I put over the perforated piece goes all the way around. I slit the piece lengthwise, spread it then pushed it over the perf section. Later closing it around the section then welding it back together. I tried to weld as much as I could on the ends too----but there's a semi circle worth that I couldn't get to.


I measured that I needed a sealing pipe with an ID of 2.65". I rummaged through some junk of mine and found a piece that was a little larger----they were most probably 3" (OD) exhaust tips. When I cut the lengthwise slit in them I took a little more----thus ensuring they would enclose the perforated section without overlapping the ends.

NHRA95

Any chance on getting a sound clip?

426 Hemi

Not the best clip but I hope it helps.

TAILWAG

sound clips will not do this mod justice.

I have a tune, intake and this mod done...493rwhp...I can't attribute specific hp to this mod...but I am sure it adds something...if not, it does sound like it does.

To those that like the Corsa sound....this is as close as it gets to it...except it sounds better.

NHRA95

Thanks 426 Hemi, sounds great!

50 4Ever

Pass by at 120+ mph... I'm the 1st vette

click here

This one is sitting still, valves closed then open, you can tell the difference....

click here...

Oli1313

How common is this mod? Do muffler shops perform this kind of work often? I spoke to the guy who was installing an exhaust on my truck about this and he looked at me as if I was an alien.

TAILWAG

if that 120mph pass does not sell this free mod against the Corsa and stock exhaust, I don't know what does....

50 4Ever

One guy in California talked to a muffler shop about and he got the same look...

Oli1313

Damn! I wish I had the know-how, the tools, and the patience to be able to do it myself. What I do have is an unlimited supply of beer and food for someone local in AZ that has the above qualifications and wants to do it.