How to unfold crimp on muffler?

[billyboy]

What sort of tool works best to unfold the fold over crimp on a muffler with out making a mess of it. Pretty tight quarters and all I can think of to use is a small screw driver and I don’t think it’s up to the task. Any ideas?

 

[Maine choppa]

Not an easy task to accomplish without a lot of distorted metal. What are you looking to do once you open it up?

 

[huskihl]

Which muffler?

Medium/large screwdriver and side cutters work well. Heat isn’t always required but getting the seam red hot first simplifies it

 

[xtremez]

I just use a propane torch and a flathead screw driver and uncrimp them. Torch and pliers when putting them back together.

 

[Woodslasher]

On a few saws/trimmers I've used a drill to make a "slit" in the seam, then used a flathead screwdriver to pry it open.

 

[billyboy]

Have a Makita DCS 520i and I would like to open it up to remove the baffle and enlarge the exhaust a bit. Leary of using heat and warping the can. Have only opened a couple exhausts and this one has me stumped. Don’t want to make a pigs breakfast of it. If I grind the fold off, could I braze it in a few spots and get it tight enough putting it back together?

Which muffler?

Medium/large screwdriver and side cutters work well. Heat isn’t always required but getting the seam red hot first simplifies it

 

[Squareground3691]

What sort of tool works best to unfold the fold over crimp on a muffler with out making a mess of it. Pretty tight quarters and all I can think of to use is a small screw driver and I don’t think it’s up to the task. Any ideas?

Heat is ur friend.

 

[huskihl]

Heat won’t warp it.

Not certain on yours. My only experience is on the 7900 and a couple Stihl models. Cutting the seam off works but you might potentially create more work in trying to clean up your welds. Carbon steel can be brazed back together, stainless steel would need to be TIG welding or silver soldered back together and that much silver is a little expensive

 

[billyboy]

My 2 Stihls are bolted half cans, easy to work on. Not looking for power on Makita so much as getting it to run cooler. No Cat. Have a 18” 3/8 LP on it and it has good power. I guess I’ll think about it for a bit. Thanks for the help.

 

[Pioneer]

I have done several muffler mods where I had to grind the crimp off. Use your bench grinder and go just deep enough to cut through the thickness of metal. After your muffler mod you can braze up the edges, and it actually makes for a very clean look. If you paint your muffler after that you can hardly tell it's been worked on.
On this one the metal was pretty thin, so I actually bent the flange on one side open a little bit to give more area for the braze.

 

[thenne1713]

Which muffler?

Medium/large screwdriver and side cutters work well. Heat isn’t always required but getting the seam red hot first simplifies it

Heating to red hot and bending while red is easiest, or allowing to slowly air cool is "annealing", where it can bend without snapping off.

<<annealing = heat (metal or glass) and allow it to cool slowly, in order to remove internal stresses and make it easier to work: e.g. "copper tubes must be annealed after bending or they will be brittle" · ..>>

 

[Lightning Performance]

Normally use a torch for 361 type mufflers. The 6401 is about the same deal. They don't look as nice as the ones cut and brazed but I have no finish work. I've seen others cut out the back of a muffler and weld it back on. The issues become the cracks near the welds. Once you weld them they need to be annealed imho. Bass don't seem to have any issues once it finished. Furnace brazed with gell or paste would be the best and the least amount of work. Drive drums are made like this and they hold up.