359 port timing numbers

[jonsered 535]

I have the muffler and heat shield and gasket opened up to the port opening.
What should |I do with the muffler just drill a couple of 1/2'' holes inside on the plate in there.
It doesn't have a catalytic converter as such like my dolmar 5105 did before I replaced it.

 

[jonsered 535]

 

[jonsered 535]

 

[David Young]

that plate is the cat.
the more of it you get rid of the better.
punch holes in it, you want to create a larger volume. also if you cut the tube off to the outlet it will help.

do a search on muffler mods for those saws, lots of info.
you can also buy an empty aftermarket one for cheap maybe 15 bucks.

some people like adding a deflector and hole on one side. I normally put a couple of 1/2" holes in the mounting bracket on the front and put some screen in there.

a muffler mod alone on those saws is an impressive power increase.

 

[David Young]

cut the tube on the red line

drill a bunch of holes where the red circles are

 

[jonsered 535]

I can do that lol. stay close to your pc as I make my progress.
I will post a Picturewhen I'm done gotta grab a sandwich first lol.

 

[jonsered 535]

That should do it no pipe there now

I can do that lol. stay close to your pc as I make my progress.
I will post a Picturewhen I'm done gotta grab a sandwich first lol.

 

[jonsered 535]

 

[sunfish]

that plate is the cat.

359/357 muffs have a internal plate/baffle & tube (cat or not). I just cut most of the baffle out.

 

[David Young]

Very nice! What are you doing for an outlet

What kind of sandwich did you have?

 

[jonsered 535]

Lol tuna and cheese
I'll leave the stock one for now and try it.
Do you think i should put her together or wait till I get some liquid steel for the intake

 

[drf255]

Your ports look good, even the exhaust IMHO.

I wouldn't of touched the intake. Did you raise the transfers, if so how?

I don't think that the intake/piston bevel will create much of an issue. Remember, there's a lot of fluid dynamics happening here. There's charge inertia filling the case and the major percentage of the port is closed at that point.

I woulda prolly sanded the base first to lower the jug slightly. I wouldn't have touched the exhaust port at all except for widening. The factory give the roof a perfect shape and it wouldn't be worth it. Plus, 105 woulda given you better compression and more torque.

 

[David Young]

Lol tuna and cheese
I'll leave the stock one for now and try it.
Do you think i should put her together or wait till I get some liquid steel for the intake

mmmm tuna melts with tomato soup.

I also like tuna with shredded extra sharp cheddar with diced gherkins on a wrap

I would not run it like that from my experience. I would cut a half moon shape in the bottom of the piston in the very center. Like what they do on the stihl ms 250 piston.

The lower intake side of the piston takes the most side load of anywhere on the piston. basically what we have done is like making the port too flat. so by putting a small crescent in the piston you would ease the piston back in line and maybe curb some of the wear.

you will likely have a long intake duration by the time you are done. you will be able to see what that runs like then put in the epoxy and bring the intake to a short duration like 142-144 and see how you like it.

have fun with it.

David

 

[sunfish]

I woulda prolly sanded the base first to lower the jug slightly. I wouldn't have touched the exhaust port at all except for widening. The factory give the roof a perfect shape and it wouldn't be worth it. Plus, 105 woulda given you better compression and more torque.

It's difficult to sand the bottom of the jug with the protruding parts that go down into the case. It's not flat like some other saws.

I agree on the exhaust port.

 

[jonsered 535]

I raised the transfers to 120 from 122.5
My exhaust is at 101.5

 

[jonsered 535]

 

[jonsered 535]

Thought I would dig it out and give more to file and less chance of a piece falling off.
David what do you mean by cutting a half moon shape got a pic

 

[sunfish]

Backing up a bit, ya need to open up the stock outlet or add a second port on the muff or all this is for naught.

 

[jonsered 535]

Backing up a bit, ya need to open up the stock outlet or add a second port on the muff or all this is for naught.

Thanks I'll pull out the mig and put another outlet there would like to put a screen there if I could also

 

[Mastermind]

Here's how we do the cat muffler....



Just make the outlet behind the plate, then cover it with a deflector. This is made from a piece of pipe.........probably an old bike frame.