M923 Exhaust Flapper

[crazywelder72]

Tomorrow I will get a better video up of the horrific clanking when firing it up.

Here is a bad video when i was trying to see the exhaust smoke color.

 

[wsucougarx]

Here's what should work. Going to start with a 3/8" bolt and work down from there if it's enough weight.

 

[crazywelder72]

I still vote for just grind or cut the pipe a few degrees

 

[crazywelder72]

Ok, I have 2 videos as promised.

The first is the flapper while letting the truck warm up (after the buzzer went off) this morning. I hod to take the little one to soccer.

The second one is later when i got home and the motor was nice and warm, just letting it cool down for a few.

 

[crazywelder72]

lets try that again

 

[nf6x]

Yeah, that is pretty clanky!

I'm about to head out to run errands, and I plan to stop by a muffler shop to see if they can make me up a straight piece of pipe with the right flange on one end. It's not a simple flare; instead, there's a separate flange welded on for the coupling to the muffler. I may still end up trimming the end of my bent pipe, but I'll try the straight one first if I can get it today. I'll bring my bent pipe with me to show them the coupling that I need on the end.

 

[crazywelder72]

The previous owner of mine cut the muffler right off. Said it didn't do much anyways. So he just stuck on a piece of 3 1/2" pipe and welded it on plus the flapper.

Keep me posted......

 

[wsucougarx]

OK, mission accomplished with a field expedited method. I used a 3/8" bolt and now the flapper closes completely The only thing I had to do was just drill a 3/8" hole.No cutting, measuring, welding, or frustration with this one. Can't get any more simple than that.

 

[nf6x]

Cool.

 

[nf6x]

The muffler shop I went to had 4" pipe, but they didn't have the right kind of coupling flange, and I didn't want to cut up my bent pipe to harvest the coupler. So I put the bend back on and pushed dirt around with my Bobcat instead.

Maybe I'll cut the bent pipe to a different angle tomorrow.

 

[dgardner]

Amazon.com: V-band Flange 4.00" - Mild Steel: Automotive

Might end up being easier to just buy another stack.

 

[dgardner]

Double post; can't delete

 

[Csm Davis]

Okay here's my two bits I have probably cranked more different 939 series trucks than anybody on this site most all been sitting two years or more and something you learn quick is to watch for water in the exhaust when you slave off a truck. So here's what we get in rain soaked south Mississippi, no stack= lots of rusty water (funny first time you are in the truck and you soak someone else) flapper on exhaust = rusty water just not as much, open curved stack turned wrong way can have some water but not much. Best in my opinion stock stack pointed in correct direction.

 

[firefox]

Does anyone drill a hole in the low point of the stack so that the water drains out?
This may not work on all types, but I was told it might work on mine which is an
M54A2. ie the one in my avatar.
Bruce

 

[nf6x]

Best in my opinion stock stack pointed in correct direction.

So, the regular, open tube pointed to the right rear and slightly downwards does the best job of keeping stuff out?

Does anyone drill a hole in the low point of the stack so that the water drains out?

I've wondered about this, too. Of course, some exhaust will come out that hole, too.

 

[firefox]

All that is needed is about 1/8" hole, so you
are not talking about a lot of exhaust.
Bruce

 

[Csm Davis]

So, the regular, open tube pointed to the right rear and slightly downwards does the best job of keeping stuff out?

As to water yes, but uncle puts flappers on some and as to keeping it shut a slight bend at the pivot point should work.

I've wondered about this, too. Of course, some exhaust will come out that hole, too.

I have had a M35 and a M816 that had holes drilled in the low spots worked on them no rust.

 

[nf6x]

I thought of something else to try out. I ordered samples of a few different sizes of those red tapered disposable plastic hole plugs/caps (Caplugs) . One of them should fit over the outside of the pipe, and one of the other two should fit inside the end. Maybe I'll just leave the pipe as it is, and plug the end if I'm not going to be driving it for a while. The plug should just blow off if I accidentally start the truck without removing it, and one should last for a long time until I accidentally shoot it across the yard. I could hang something like a "remove before flight" streamer off it, but I probably won't bother.

The samples were free... if I want more, they cost a bit over a buck each and come in packs of 50, though. My usual industrial supplier carries them, but not in those larger sizes, so I ordered the samples direct from Caplugs.

I'll let y'all know how they fit once I get the samples. I don't know whether I'll prefer one that pokes inside the pipe like a cork, or covers the end like a cap, so I'll try both ways.

 

[Csm Davis]

nfx6 I lived in your part of the world and would think that the flapper would be the way to go or the capplugs, you will have way more problems with dust and critters than water.

 

[nf6x]

I got the Caplug samples and tried them out today. Part number T-502 fit very nicely inside the end of the pipe. As an experiment, I pulled the emergency stop to keep the engine from actually starting and then cranked it for a moment, and the caplug popped right out and landed a few feet away.

Part number T-1064 fit over the outside of the pipe, but it wasn't quite as snug.

I just got one each of a few sizes to try out, as free samples. I don't know of any dealers yet who sell the T-502 size in small quantities (I haven't looked too carefully yet, either). Caplugs sells them directly, but they come in 50-piece packs costing over $50. So, this isn't the greatest option out there, but I'll try using the one I have during periods of inactivity rather than hacking up the pipe to accept the exhaust flapper.