Changing M931 muffler to spark arrestor

[tobyS]

My rebuilt M931 has a muffler entirely rotted out on the bottom. After getting it off, I find the top is welded at the seam about 20% and not 100%. Water pours in and with heat from running occasionally, rusts out in only a couple of years, blowing exhaust into critical air lines.

I wanted a US Forest Service approved muffler or spark arrestor, to legally operate in forestry and have chosen a Walker spark arrestor #21582. It's 4" in and out, general purpose and I found it on-line under $115. It is round, not oval, so I will have to alter brackets, but I'll keep it exiting at about the same spot and retain the guard.

So now I'm waiting on delivery and looking for a new gasket like at the bottom of the (old) muffler. A truck supply store stocks other pipe connections is nearby.

I will take some pictures and add them.

 

[JohnnyBM931A2]

Cool Can't wait to see the pics

I agree that the stock muffler is a pretty terrible design. The bottom seam is not fully welded either. I would like to get a stainless muffler at some point, somewhat close to the size of the original muffler. That way I don't have to worry about it rotting again. Then maybe have it powdercoated flat black to match the pipe and top stack (unless the regular barbecue paint is able to adhere to the stainless.)

Or maybe I will go the same route as you

 

[98G]

I tried bbq paint on the stock exhaust and it came off in short order. I can only think stainless would be worse adhesion...

 

[JohnnyBM931A2]

Really? I've always had good luck with the Rustoleum high temp paint.. I used it to paint the exhaust on my '66 Fairlane, and it still looks great after a few years. Granted, I do prime the heck out of whatever I am painting.. Always multiple coats of primer, followed by multiple coats of paint.

I guess I'll found out soon enough if I have the same issue, since I painted my pipes and new muffler from Floridianson with that paint. So far it's holding up great, but who know

Regardless, I think powdercoating would be the way to go with a new stainless muffler. What I would love to do is take my old muffler to a muffler shop, and have them make the exact same thing, but in stainless. That would be awesome

 

[tobyS]

I started to make a stainless muffler, using the old as a model, but decided against it. In fact, Johnny, if your serious about making one, I cut SS sheet for the body and formed it to the oval and also cut the 4" SS pipe, leaving a little extra at the top, where it would be a slip on. I didn't make the top or bottom, or the interior ribs yet, but have enough SS sheet for them. Only part that was to be used from the old is the flange that works with the gasket and clamp, which would be welded to the SS 4" pipe.

Since I want my truck for forestry, I decided to get one that is US Forest Service approved.

 

[tobyS]

Here is a photo inside and the components I was making for a SS one.

 

[tobyS]

The spark arrestor came and I purchased a 4" elbow, 18" x 18". I cut about 6" off of the straight end for the incoming side and cut the flange from the muffler. It fit the straight pipe and was welded. I'll post a couple more when the spark arrestor is on the truck. So far I've spent around $150+ time.

 

[bluebones]

Hi tobyS,
Do you think the spark arrestor will change the way the tuck will sound?

 

[tobyS]

Hi tobyS,
Do you think the spark arrestor will change the way the tuck will sound?

Someplace between a muffler and straight pipe. It's not near as heavy weight, but I don't know how that will affect the sound.

 

[JohnnyBM931A2]

Ha. Hopefully it's not too loud for you The NHC250 isn't exactly a quiet engine even in stock form.

 

[tobyS]

Ha. Hopefully it's not too loud for you The NHC250 isn't exactly a quiet engine even in stock form.

This is an 8.3 turbo and I've been running around the farm with the top pipe sitting down where the muffler was, so it has to be quieter than that.

 

[JohnnyBM931A2]

This is an 8.3 turbo and I've been running around the farm with the top pipe sitting down where the muffler was, so it has to be quieter than that.

Ah. My bad. You said M931 in the first post, so I didn't realize you had an A2.

 

[tobyS]

Ah. My bad. You said M931 in the first post, so I didn't realize you had an A2.

Yeah, an A2. It has about 17 hours on it since a RR rebuild in 2012 and the muffler is gone. I wonder what our government paid for that muffler?

 

[Csm Davis]

Yeah, an A2. It has about 17 hours on it since a RR rebuild in 2012 and the muffler is gone. I wonder what our government paid for that muffler?

The muffler wasn't replaced by Red River I would bet money on it not knocking your truck but the Red River depot has been the worst rebuilt trucks I have come across most are just repainted and shoved out. As I got deeper into the trucks at RSMS CAMP SHELBY I saw more and more trucks with fresh (RR rebuilds ) many with less than 10 miles on them since RR and they were sent to RSMS to be rebuilt from the ground up, and many had major systems failures, I think we still have one here with a bad motor. Look around Steel Soldiers and you will find several threads about them.