422/425 exhaust muffler

[Marks481]

I have the external muffler on my PT422. I am working (and will complete someday when my welding skills get better) on a new exhaust manifold.

Last time I took the muffler off to measure it, I also drilled out each of the intake tubes on the muffler to get rid of the 1/4" - 1/2" lip where PT misaligned the holes in the exhaust manifold and the stub tubes.

Since then, my tractor has not backfired once after long, hot mowing sessions. Previously, everytime I shut it down, I would get a couple of loud backfires. Kind of interesting that 3 minutes with a 3/4" drill bit and my drill press made that much of a difference.

 

[BobRip]

I have the external muffler on my PT422. I am working (and will complete someday when my welding skills get better) on a new exhaust manifold.

Last time I took the muffler off to measure it, I also drilled out each of the intake tubes on the muffler to get rid of the 1/4" - 1/2" lip where PT misaligned the holes in the muffler and the stub tubes.

Since then, my tractor has not backfired once after long, hot mowing sessions. Previously, everytime I shut it down, I would get a couple of loud backfires. Kind of interesting that 3 minutes with a 3/4" drill bit and my drill press made that much of a difference.

Have you got pictures?

 

[Marks481]

no pictures.

Not much to see, previously looking down the stub tubes that go from the exhaust manifold to the engine, you could see a maybe 1/4-3/8" lip at the manifold (shaped like a crescent moon... I believe the holes in the manifold were drilled about 1/4" out of position, and PT never bothered to clean them up after welding the exhaust together).

Chased them out with (I think) a 7/8" drill bit, and now there is no lip.

Notice my correction above about where the problem was (although I do wonder what the hole between the exhaust manifold and the muffler looks like).

 

[BobRip]

Can you feel the power difference? Nice catch of a problem by the way.

 

[Marks481]

no difference in power. I still get some dieseling when shutting down, but the backfires were starting to worry me so it is nice that they are gone.

I suspect that replacing the exhaust manifold entirely will help, since it could reduce the underhood temperature. Time to break out teh wleding torch and try again (my last attempt warped too much cause I had too much heat on it). First attempt at welding round tubing.

 

[KMA]

I know this has been said many times before, but it really would be great if someone could come up with a replacement exhaust manifold design for the PT422/425's and maybe even suggest replacement muffler(s). I'd like to do it myself, but I don't know if I'm smart enough...

Like many on here, my 422 gets too hot in the manifold / heat shield / gas tank area. Either a more "efficient" manifold, or maybe a dual muffler setup seems like the two options. I know some others have done exhaust mods, but I don't know if we've established one "go to" solution that should work for most people. My other big issue with the stock muffler is that it points straight down. There is could be safety related reasons for this, but it burns grass even if you only sit for a minute, and it kicks up a cloud of dust when working with dirt. I have to clean my air filter ever day or so as I spread a large mound of soil around a new wall I built.

Anyway... thought I'd vent.

 

[Marks481]

I am learning to TIG. Round tubing is much more challenging then the flat plate or square tubing that I have done to date.

So far I have managed to turn a pile of 1" schedule 10 SS-304 tubing and elbows and flat plate into something that has corners of less then 90 degrees and has to be cut apart so I can try again.

I haven't found anybody who will custom mandrel bend 1" 16 gauge stainless or mild steel tubing, which would make the whole process about 100% simpler (3 welds instead of 6). Nobody locally has mandrels that small.

If I finally give up on this plan, and go to an exhaust fabricator, I will keep your request in mind, LMA, and buy two manifolds.

 

[Phils]

Tim,

This weekend I hope to pull my exhaust 'system' off my 422 and see if mine needs to be drilled. Thanks for the tip!

Phil

 

[Gravy]

I am learning to TIG. Round tubing is much more challenging then the flat plate or square tubing that I have done to date.

So far I have managed to turn a pile of 1" schedule 10 SS-304 tubing and elbows and flat plate into something that has corners of less then 90 degrees and has to be cut apart so I can try again.

I haven't found anybody who will custom mandrel bend 1" 16 gauge stainless or mild steel tubing, which would make the whole process about 100% simpler (3 welds instead of 6). Nobody locally has mandrels that small.

If I finally give up on this plan, and go to an exhaust fabricator, I will keep your request in mind, LMA, and buy two manifolds.

If you find a willing and competent fabricator, please start a new thread. There may be enough of us for a group buy.

 

[washita]

at the moment cannot find the link but search for exhaust pipe in the experimental airplane engine websites prices were better than buying through the local dealer who supplies gen sets for rv's even after changing my exhaust sytem it will glow slightly with 87 octane and no glow with 89 or 92 octane ironically I changed my exhaust after finding a tree with it personaly I would prefer a light weight dual system pointed straight up or angled back 5 to 10 degrees so the tires would still protect the pipes in case of accidently backing into another tree

 

[KMA]

I drilled out the misaligned holes as Tim suggested. It backfired the first time I shut it off after only running for a little while. The good news is that it didn't do it the second time I ran it, which was for even longer. So I'm still not sure how much it helped yet, but it definitely didn't hurt and was easy enough to do.

To stop my PT422 from burning my lawn when I stop for a few seconds or from kicking up ton's of dust when working in dirty areas, I decided to do something simple and cheap since I do not own welding equipment (yet). I picked up a 1 1/2" copper elbow at the hardware store today and drilled a hole through my exhaust tip for a bolt. I added another set screw to keep it from vibrating.

 

[Marks481]

Looks like it works better then what I did. I took a cast iron elbow, and with a little work with a file, I was able to shove it over the tailpipe (same orientation). It fell off last summer, and I haven't put it back on,

Last time I mowed, I think I burned a couple spots in the lawn. I guess it is time to find that piece of angle pipe.

 

[Red Zebra]

no difference in power. I still get some dieseling when shutting down, but the backfires were starting to worry me so it is nice that they are gone..

I may pull my exhaust and have look too.

I did discover that after a running the 425 long enough to kick on the cooling fan, I let it idle at about 1/4 throttle for about 5 min (long enough for me to blow grass clippings out of all the nooks and cranies after mowing) it shuts
down without a hic-cup.

FWIW


Jim

 

[KMA]

Okay, I used my PT a few more times since following Tim's idea of drilling out the misaligned exhaust holes and it hasn't backfired again. It does run-on a bit if I shut it down hot as Tim mentioned.

I did discover that after a running the 425 long enough to kick on the cooling fan, I let it idle at about 1/4 throttle for about 5 min (long enough for me to blow grass clippings out of all the nooks and cranies after mowing) it shuts down without a hic-cup.

Jim, I do the same thing normally. I also turn on the auxillary radiator fan I mounted to the side before letting it idle a few minutes. Then it shuts down fine. After drilling out the exhaust, I have been shutting it down quicker just to see what effect it had on the back firing.

 

[Red Zebra]

....It fell off last summer, and I haven't put it back on,Last time I mowed, I think I burned a couple spots in the lawn. I guess it is time to find that piece of angle pipe.

Let the mower find it!

 

[Red Zebra]

That's what my dad would have called "Southern Engineering". Beautiful!
It's where function meets creative problem solving! Love it!