Pontiac Firebird 1967-2002 - cutting the car to accomodate bigger mufflers

i HAVE to make this car reasonably quiet, but i'm not giving up my X-pipe setup. so i'm cutting out the sides of the rear compartment area (where the T-tops go) to fit magnaflow offset/center 5x8x14's.

so the full exhaust will consist of long tubes, magnaflow cats, 3" x-pipe, dynomax bullets in front of the axle, magnaflows in the back, and borla 4.5" defuser tips.

i've never seen anyone do this, but i'm expecting it to sound very good.

stay tuned.

This would be a quick way to seriously drop the value of the car. And that section of metal makes up some of the design strength of the rear body. If you get rear-ended, the car may suffer more damage than if you left the stuff alone. And if your insurance company inspects it afterwards, they may not cover any damage or injuries.

This would be a quick way to seriously drop the value of the car. And that section of metal makes up some of the design strength of the rear body. If you get rear-ended, the car may suffer more damage than if you left the stuff alone. And if your insurance company inspects it afterwards, they may not cover any damage or injuries.



I don't care about the value of the car. It's a 99 WS9 formula with 140k miles on the body. Full coverage would be a waste of money.

And the part I'm modifying has NO contribution to the strength of the car. I'm not cutting the frame rails or the rear support. I'm simply raising the floor of the rear compartment..... And i may just add some strength while I'm at it.

Your criticism may have been intended well, but it comes off as condescending. This will not be a hack job.

Sorry, it wasn't intended as such. I was just thinking of the possible consequences. I did think your post was looking for opinions.

If you add some metal back in and do good welds, I'm sure you'll be fine.

Pics when done please.

The original plan was to just make notches, but i realized it would be easier to just raise the whole floor. It should decrease drone too, theoretically. it'll also be easier to mount my sub to a flat surface.

Lot's of us have deleted the entire t-top well area for weight reduction on our race car projects. Have pics in the thread for my '95 'bird build if you're interested.

You guys did some hard core fabbing lol.

I cut part of my back seat pans out to fit my bullets for my true duals after i lowered my bird. just welded in some square bar and sheet metal. then trimmed the seat pads so they would still fit.

they don't make any kind of muffler that fits your needs / space with out cutting the unibody?

wheres the gas tank in relation to where your putting these mufflers?

I would really look at making a custom muffler before I started hacking up my car.

I'd be concerned about safety in the event of an accident. what if some bimbo in a big ass truck rear ends you? no matter what you do, you've changed the way the car responds to an impact and it's designed crush zones.

they don't make any kind of muffler that fits your needs / space with out cutting the unibody?

wheres the gas tank in relation to where your putting these mufflers?

I would really look at making a custom muffler before I started hacking up my car.

I'd be concerned about safety in the event of an accident. what if some bimbo in a big ass truck rear ends you? no matter what you do, you've changed the way the car responds to an impact and it's designed crush zones.

1. No. The biggest mufflers that fit are still way too loud.

2. In the very back where the tail pipes go.

3. Your third question has already been addressed in this thread.

I have 5x8x14 magna flows mounted back there.... no cutting. We did have to do some bfh taps but no cutting.
http://i23.photobucket.com/albums/b371/sleeperfc/2012-08-22_14-39-32_436.jpg
http://i23.photobucket.com/albums/b371/sleeperfc/2012-08-22_14-39-09_164.jpg

You guys did some hard core fabbing lol.

Yep! I sure did on my '95. I wouldn't go that radical on my '00 though.