I just tried installing the Flowmaster American Thunder kit on my 2007 Mustang GT. It seems like no matter how tight I tightened the exaust clamps the exhuast just would not tighten down. I'm sure I had the clamps positioned correctly. I kept tightening them, then started the car and checked for leaks (found leaks) and tightened them again. Finally the drivers side bolt got so tight it began to strip (yes, I was using the correct 15mm socket) So I undid the muffler brackets and even though I tightened the clamp down so tight that I stripped the bolt the muffler just pulled off as if there were no pressure on it at all. Now I'm stuck with a Flowmater muffler with clamp on it (the clamp is on the muffler with tightening tension big time) and a stripped bolt. How am I going to get this clamp off??? Id there a difference from the 05/06 Mustang exhaust and the 07 Mustang Exhaust?????........What's up with this????.....Does anyone have any info???? I'm very disapointed in this kit. This should not have happened........That clamp was on there so friggin tight how the heck did the muffler slide off (thank god it did though because that bolt is stripped to hell).........Going to call Flowmaster tomorrow.....hope they make good on this................Does any know if the clamp has to be slid all the way to the very top of the Muffler or can it be positioned pretty much where the stock one was.......just doesn't make any sense.

 

Maybe they changed the location of the nipple

 

The "fit " seems to be spot on. Clamp just won't compress the steel. In regards to the clamp do I have to place a clamp ring on each side of the stub???

 

I had the same issues on my 06; I tightened the clamps to the point that I broke the clamp. I went to the auto parts store and bought 2 saddle style muffler clamps and fixed my leak issues for good. The clamps supplied by Flowmaster are garbage.

 

took the words right out of my mouth - trust me, you'll be a LOT happier with new clamps

 

Hmmm...I don't get that. I just put Flowmasters on my 06 GT and they fit very tight with the supplied clamps. I don't even have them tightened down all the way. I know the Flowmaster pipe has a notch and the 06 exhaust tube has a nub. I positioned the nub all the way down into the slot and the clamps are about 3/8" down from end of Flowmaster pipe, just under the notch. They don't budge and there are no leaks.

 

Issues regarding the over-axle clamps pulling loose and tips not centering in the bumper cut-outs are the result of excessive preload of the pipes from the 'H' to the tip.

The mid-pipe clamps (just rear of the 'H') must be loosened along with the over-axle clamps. Once the clamps are loose, center the tips and tighten from back to front.

Doing this will remove the preload, center your tips, and keep your pipes from pulling out from the clamps.

 

I had to retighten the clamps several times due to rattles. I finally said screw it and use my impact wrench and tightened the bolts until to they screamed. No leaks, no rattles, no problems. But it definitly wasn't a plug and play install.

 

Hey, thanks! That sounds like it might fix my problem. Just what I was looking for.

 

My flowmasters fit loosely over the end of the exhaust pipe, and the clamp wasn't doing it. Instead of trying to squeeze the metal and wrinkle it to get it to fit, I used a circular saw with a cut off blade and cut 2 slots in the flowmaster end (one on each side of the pipe) so that the metal had some where to bend to when I was clamping. Worked perfectly. I already had marks on my pipes from the clamp, so I used them as a guide and didn't cut in much further than they were, because I didn't want to create a leak that way. The cut-off blade I used is about 1/8 inch thick, which removed plenty of metal for the sides to colapse. I did the cut perpendicular to the slot that's there for the alignment bung.

The tips on the mufflers lined up perfectly with the bumper cutouts, they look better than they did on the '05.

 

Thanks for some of the info guys. Not to keen on cutting slots in the pipes on the Flowmasters to get them to fit. I Don't think I should have to do that. Going to try some better clamps first. Flowmater makes great sounding mufflers but I think this American Thunder Kit as a whole for S197 needs improvement. I'm going to take another shot at it after I get through with my eleven hour work day.

I DON"T RECOMMND BUYING THE FLOWMASTER AMERICAN THUNDER MUFLER KIT FOR S197 MUSTANGS.FIT AND FINISH IS POOR. MODIFICATION TO THE PRODUCT IS MOST LIKLEY REQUIRED.

 

My initial problem was self-imposed. I had the passenger side clamp slightly on the stub. Rattled and leaked. Loosened it up, moved the clamp and tightened her down. Zero problems since.

 

I notice all of you guys who have had really no problems have 2006 Mustangs. Me and JayGuy both have 2007's and had the same problem. I wonder if the piping on the exhaust is different in some way (not sure....maybe material). I socked down the bolt so tight with the proper socket that I stripped the bolt. The clamp was super tight. The muffler just pulled off like there was no clamp at all. I had to cut the clamp off with a hacksaw. You should have heard the clamp ring "pop" as I got through cutting them......That clamp was on with some serious torque but it just wouldn't tighten the exhaust. For those of you who used saddle clamps what size did you use? I know the exhaust is 2.5" but the flowmaster inlet flares open for the over axle pipe to slide into.........This is very strange.....

 

I have the same problem Taco Bill described but I have SLP's.
Haven't had a chance to try his solution yet, but when I do, I'll be sure to report the results.

 

Hey Jason, I'd love to take the credit for the mid-pipe clamp idea, but I've read about doing that several months ago here in TMS.

I'm just keepin' that solution alive.

 

My pipes are pulling loose when I psysically pull them (with very minimal force) not while driving. Not sure if TacoBills solution fits my problem. The mufflers center perfectly and fit very well over the mid pipe over the axle. I think the clamps provided in the kit are just garbage. I need to get some good stainless saddle clamps......If that doesn't work maybe I'll have to cut slots in the Flowmaster inlet pipe like Jayguy said. The stock mufflers have slots in them for them to compress onto the mide pipe over the axle. I have never had such a hard time clamping two pieces of exhaust together........And I've done a lot of cat back/sectional exhausts on my cars over the years........I clamped that pipe so tight,,,,,how did I just slide it off with ease.......maybe I have super human strength????

 

I had the same problem with mine. The inside diameter of the Flowmaster pipe is too big compared to the outside diameter of the stock pipe over the axel. When you clamp it down with the supplied clamp, it just doesnt have enough pressure to compress the tubing to fit tightly over the stock pipe. I even used a 4ft breaker bar to try to get it as tight as I could and I ended up snapping the nut right off the clamp....and it was still loose! I had to use a hacksaw and a pry bar to get the broken douchebag clamp off. Then I just went and picked up a couple U-style muffler clamps and cranked it tight.....and that did the trick.

The only drawback is that if I ever want to take them off, its going to be a pain since I compressed the tubing so tight that it will be hard to take them off.

 

I think the problem is the outter diameter of the stock pipe is smaller than it was on older cars. And with the clamps that come with the Flow masters, or just about any clamp, the only way to make up that difference is to compress the muffler tube until it fits that smaller od on the pipe. If you don't slot the pipe like I did, then you're trying to compress the metal of the tube and the clamp itself is going to hinder this process. You could try shimming the connection with pieces of aluminum (cutting up an aluminum can or two works, had to do that to mufflers on my bike several years ago) but that's a temporary fix, and those shims could work their way out over time. I would suggest slotting the outer pipe like I did, it's simple and very effective. And I'll bet if you take your car to a muffler shop that's going to be their first recommendation, and second will be to weld the connection completely.

Good luck, whatever you decide. Next time I've got the car in the air I'll try to get some pics of how I did it. Not sure when that will be though, kinda booked for the next few weeks.

 

I put the stock mufflers back on. This car doesn't even have 400 miles on it and it discusted me to have it sit in my garage with a set of Flowmaster on it that I can't get to secure properly. I'm going to slot the pipes like jayguy suggested above. It won't be hard and it should be a good solution. Maybe next weekend. This weekend I'm booked.....and I want to drive the car this weekend too. Little worried about creating potential leaks by doing this but it's worth a shot. Pics would be great Jayguy if you get a chance. I just don't want to cut to far. This is poor design on Flowmasters part. I notice the Borlas come slotted in the pics on their website. Stockers have slots in them too. Shame on Flowmaster for this. It's a simple engineering concept to slot them.........Wonder if it's worh calling them....Thanks for the info guys.

 

I'll see if I can get the car up tonight so I can take pics of the mufflers. I'll at least get a pic up of the blade I used to cut the slots with on my Makita 10" circular saw. I know what you mean, I was starting to put the stock mufflers back on when I remembered I had that blade, and thought I'd give it a try. I had 74.4 miles on the odometer at the time, by the way.