Easy dolmar 5100/5105/510/460 muffler mod

[nstueve]

I know guys have complained about the cat mufflers considerably and finally had a Dolmar 510 show up in the shop. Took lots of pics and should have a pretty easy break down for you guys.

Choices:
1.) buy an early non-catalytic muffler
2.) mod the one you have.

Let's start with the early non-stainless non cat muff. This would be the one on the far right. Decent design but several "flaws" in OEM off the shelf condition. Also it's galvanized and not particularly awesome to be breathing the fumes from re-welding.

First I opened all of them using an angle grinder and flap wheel to grind off the rolled edge. Yes you can use a torch and heat and un-crimp it but I don't have a torch...

Be sure to only take enough material off to break through the rolled over edge. DO NOT grind down until flush!!! You'll see/read why later.

Ok inside the non-cat muffler. While the baffle isn't horribly restrictive... Well it still is. Also the exhaust outlet hole is dimple dyed (necked down) inside; seen in the upper left corner of the muffler 1/2 on the right.

The outer baffle really prevents you from correcting the small outlet since it is welded on... Grr!

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[nmurph]

I take a cut-off disc on the Fordom and remove deflectors, then open up the stock opening and braze everything back together.

I'll be watching...

 

[nstueve]

Ok so the modification will start with cutting the inner baffle out.

The inner baffle actually pops out in one piece. I then cut the baffle free from the rear base pad that you will need to keep proper spacing. The anti crush sleeves connect with the base pad seen in 2nd pic below

See the little ears? Keep those, everything snaps together easier then.

I will open the inner exhaust hole. And Shaun Carr will be tig welding these back together. This muffler mod to this point took me 10mins. Think Shaun will do the welding for $20ish??? I'm sure he'll chime in later. Keep in mind I am going for tig welding so I can keep the "stainless" factor of the muffler. The tig also leaves a pretty clean look. Will take pics of welded up mufflers and post later. Last thought is that I don't know if I like the older style outer baffle allowing exhaust flow forward and backward.

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[LowVolt]

Looking good.....

Can't wait to see it welded back together.

 

[nstueve]

Now to the stainless. There are 2 options I've found.

1.) cut the cat out of the inner plate
2.) take inner plate out entirely

Option 1.
Grind open. Notice the perfect square metal rim in the background? That's what you get when you don't overgrind!

There are 3 spot welds that you have to cut or grind away in order to release the Cat from the inner plate.

Couple problems with
The above. First you need a Dremel or Foredom with carbide to grind the welds b/c they are tucked into tight spaces. 2nd seen below is that the inner plate is left in and the inner exhaust tube remains. This would probably still be a little restrictive and keep the dB's down a little (save hearing). You can see the tube running the entire top of the muffler 1/2 in my hand on left.

Muffler plan is to open the 2nd exhaust hole (seen on left 1/2 above) and tig back together. Exhaust will run in the two holes and up and around to the OEM outlet. OEM outlet is actually pretty substantial on these Cat units.

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[SteveSS]

Subbed for updates. Looking forward to this one.

 

[nstueve]

Want more extreme and easier yet??!

Drill the 8 spot welds holding the inner plate out; seen in pic below. This removes the cat and the restrictive tube (also seen in pic) and the cat element. Now I recommend a spot welds cutter or being more careful than me. I drilled through both the metal plates. You can also grind them with a Foredom or Dremel.

Here's all the pieces...
Removed cat and tube on top left. Front and rear 1/2's on top right. Front muffler cover and outlet baffle seen in front

The one problem with this route is the outer muffler baffle (seen above bottom) bolts into nuts that were welded to the Cat plate.

Solution. Shaun can weld 2 nuts into the front of the muffler. Below pic is of the outer baffle with the bolts poked through the front of the muffler.

Pic below is a pic through the muffler as it looks without the outer most deflector/baffle.

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[nstueve]

Last thought about stainless mufflers for the night is that even if you drill the spot welds all the way through (like i did), Shaun can weld the holes shut and you still have the pretty front muffler cover to hide the ugly... Below pic is of the hollow muffler with front cover and no inner tube with the spot welds drilled all the way through.

More pics of finished product and MAYBE some videos of the 510 running with each of the three options to come.


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[srcarr52]

Argg. I hate tig welding in drill holes. Get a spot weld cutter already!

 

[nstueve]

I want one of those picks and a super scraper like you have...

Going to Shaun's tonight whether he wants me or not. Stay tuned for new pics and movies after the snow storm...


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[LowVolt]

 

[srcarr52]

I want one of those picks and a super scraper like you have...

Going to Shaun's tonight whether he wants me or not. Stay tuned for new pics and movies after the snow storm...


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Pick set.
http://www.amazon.com/Forney-70710-4-Way-Pick-4-Piece/dp/B000CFNBR2
Even cheaper.
http://hardwareonlinestore.com/inde...lgonqT5moLxyfrLz7OCOZDsWoSzgJQLBivhoCfvPw_wcB

Super scraper.
http://www.amazon.com/gp/product/B0..._m=ATVPDKIKX0DER&pf_rd_r=1FZEHT94G511WT8EQMRS

Good thing you didn't take a video of me welding in the 9 holes you drilled into the one muffler, there would have been a lot of profanity. :****you:

 

[nstueve]

So here is the "Mad Hatter" at work...

Notes from Shaun.
1.) don't be a dumbass (like me) and drill through the welds holding the two front cover pieces together. Use a spot weld cutter and leave excess behind if you fell the need to remove the inner plate like I showed above. He doesn't like plug welding.

2.) send the proper nuts for the small outer baffle if you want to remove the inner plate

3.) pre-grinding the edges is preferred so he has clean metal to tig back together. Top and bottom. See pic below: see the shinny ground edges around the outside.

4.) leave as much of the crimp ridge as possible around the outside. It gives him something to pull together with the vise grips and takes less tig rod to close back up.


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[nstueve]

Finished product...

Notice
The two 1/2's have a different color. I don't know if it's different metals or two different grades of stainless. I just noticed the difference in the shop last night. Those are paired muffler 1/2's.

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[nstueve]

this shows the two different styles that I was going for. One is a compete empty can and the other still incorporates the empty inner tube.

The top deflector cover also has stainless screen tack welded to it. Owner chose for me to remove the screen.
1/2 screen gone

All gone

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[nstueve]

Last note: if you've made it this far... I'm sure Shaun can quote you for dis-assembly/grinding/pre-work on either side.

I also have a "core" cat muffler I can provide Shaun to mod for you. This would allow a strait muffler for muffler trade via USPS with minimal saw down time.


Videos forthcoming.

Question for nmurph... What are your base carb settings after modded muffler on these saws?

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[LegDeLimber]

I'd wager the heat from the cat is what took the front half to that wheat color.
Take a look at the heat discoloration regions and how they follow a flow pattern of both radiant and physical contact.
A crimped seam won't quite carry the heat like a brazed or welded one.

Until you've (unintentionally) torched a nut off of an old bolt that's all a bit rusty and left the threads almost intact,
You really don't just feel the respect for what just a thin oxide layer can do to block heat transfer.
Salvage cutting was interesting and educational at times.
Some days were probably as mind challenging as Pro Timber Falling.

 

[Homelite410]

You call this process easy?

 

[nstueve]

You call this process easy?

1.) grind
2.) drill/grind to remove cat
3.) shaun tigs it shut

or
1.) trade shaun for a fully modded muffler.

Seems really easy to me!
There is way more detail in here than i really needed to add.

 

[Homelite410]

1.) grind
2.) drill/grind to remove cat
3.) shaun tigs it shut

or
1.) trade shaun for a fully modded muffler.

Seems really easy to me!
There is way more detail in here than i really needed to add.

Ha!