My first semi-professional-looking muffler mod (395XP)

[Brmorgan]

I finally got my stick welder working since modifying it for DC output, so I decided to try it out by doing a muffler mod on my Husky 395XP. Talk about an exercise in patience! Adding the DC rectifier stack to the welder causes a net ~20% or more power loss, so that brought the minimum amperage of my AC stick welder down from 40 to around 30 or so. I used 5/64 6013 sheet tacking rod. It welded OK but the problem with 6013 is that you cannot go back over ANY slag, or it will create a fault in the bead, especially at these low amps. So if (more like when) you blow a hole through and have to fill it back in it's a real PITA. I know it's not the prettiest weld job in the world - I would much rather have used a MIG but don't really have access to one. I think it turned out OK though and looks better than brazing IMO. It sure woke her up a bit! And my ears... Pretty quick through 20" fir - now I need to time it against the 660 since they're both modded. And throw it on the mill again.

The new port comes out straight across from the original one. The original one did seem quite large to begin with, and must be close to the exhaust port size, so I didn't use a really big pipe for the new one. It's just steel electrical conduit pipe.

Unfortunately due to the placement of the port I had to cut some of the top shroud away to fit the muffler. I don't care much, those covers are easy to find around here if I ever wanted to replace it. And the cut doesn't look out of place with that port there. I didn't have many options for placement - straight out the front wouldn't be great because it would be restricted when used for milling. And out towards the side would be blowing in my face when milling.

The weld was nice and shiny before I fired it up and made a few cuts. Makes it look horrible in the pic. I don't have a tube bender (yet) so I put one tube coming out of the muffler at 45 degrees, then a small wedge piece with 15 degrees on each end, and finally the straight pipe with another 15 degree end - all added up to 90 degrees, so the pipe comes straight out the front. I might grind the welds smoother with a Dremel, but I'm not sure yet.

Yep, that's a full wrap and skip chain! Rather have the half-wrap for milling though.

Any tips on painting the muffler the stock flat black? I've never dealt with high-temp paint before.

 

[pioneerguy600]

I finally got my stick welder working since modifying it for DC output, so I decided to try it out by doing a muffler mod on my Husky 395XP. Talk about an exercise in patience! Adding the DC rectifier stack to the welder causes a net ~20% or more power loss, so that brought the minimum amperage of my AC stick welder down from 40 to around 30 or so. I used 5/64 6013 sheet tacking rod. It welded OK but the problem with 6013 is that you cannot go back over ANY slag, or it will create a fault in the bead, especially at these low amps. So if (more like when) you blow a hole through and have to fill it back in it's a real PITA. I know it's not the prettiest weld job in the world - I would much rather have used a MIG but don't really have access to one. I think it turned out OK though and looks better than brazing IMO. It sure woke her up a bit! And my ears... Pretty quick through 20" fir - now I need to time it against the 660 since they're both modded. And throw it on the mill again.

The new port comes out straight across from the original one. The original one did seem quite large to begin with, and must be close to the exhaust port size, so I didn't use a really big pipe for the new one. It's just steel electrical conduit pipe.

Unfortunately due to the placement of the port I had to cut some of the top shroud away to fit the muffler. I don't care much, those covers are easy to find around here if I ever wanted to replace it. And the cut doesn't look out of place with that port there. I didn't have many options for placement - straight out the front wouldn't be great because it would be restricted when used for milling. And out towards the side would be blowing in my face when milling.

The weld was nice and shiny before I fired it up and made a few cuts. Makes it look horrible in the pic. I don't have a tube bender (yet) so I put one tube coming out of the muffler at 45 degrees, then a small wedge piece with 15 degrees on each end, and finally the straight pipe with another 15 degree end - all added up to 90 degrees, so the pipe comes straight out the front. I might grind the welds smoother with a Dremel, but I'm not sure yet.

Yep, that's a full wrap and skip chain! Rather have the half-wrap for milling though.

Any tips on painting the muffler the stock flat black? I've never dealt with high-temp paint before.

The welds look a little rough,LOL. They will work alright and the port out the front looks really good. I sandblast all my mufflers with 00 sand and then paint them with high temp barbeque paint and it turns matte black when dry. I have used high temp engine enamel but it burns off quickly, less than a months steady use and its mostly gone. I hear there is a high temp with ceramic being used by some members and it works well but curing paint foes not interest me enough to try it yet. Good cleanup and degreasing is probably the most important part of any paint job. IMO Pioneerguy600

 

[dave76]

So you used some 1/2 inch EMT. Looks good, is the other port still open???

 

[Wirenut2266]

Props to you! If you know how to add a rect. bridge for power gain/loss, i'll give you a thumbs up! As too the welds, no it's not as nice as a mig/tig weld, heck looks good, got the job done. Look at what you had too work with. Be careful on low power settings on your welder with rect. bridge assy. Yeh, it can give you alot less power or gain depending bridge, But the heat built up across the components is HUGE. Us them sparingly, you will be okay. Any real production welding, forget about it. You'll smell it when trouble arises. Still, looks sweet! Bruce

 

[spacemule]

I think if you used a drill bit to cut the corner out of the shroud, giving a rounded corner instead of square, you'd be less apt to get stress cracks there and it would look a little better.

 

[Brmorgan]

Dave - Yeah, the other port is still open. And the pipe is bigger than 1/2", I'd say almost 3/4" O.D.

Wirenut - I'm not too worried about killing the rectifier. It's made up of four huge 250 Amp stud diodes mounted to heatsinks and wired in a full-wave bridge. I've used the welder up to 175A with them and the diodes barely get warm with the rather short runs I do. The rectifier is a permanent fixture on my welder now - I took two old off-code disconnect boxes from work, combined and rebuilt the contacts, so that I have a 2-position closed switch instead of open or closed. This lets me switch between AC or DC (but not under load!) without unplugging cables or anything. Maybe I'll take a pic of the rectifier. And I'm not necessarily using the rectifier to get a lower current output, but the inherent efficiency loss ends up being a bonus when working with very thin steel. I tried sheet metal @ 40A AC a long time ago and it burned through a lot easier, not to mention a really messy weld (AC sucks).

Spacemule - if I understand you right, you mean on the inside corner of what I cut out? Good idea, makes sense to me.

Now on to the next project - an adjustable combination between a Mini-Mill and Beam Machine so I can square cants a lot easier.