MS 360 Port #s : Paging Gypo & Others

[blsnelling]

I just picked up a MS 360 Pro in the Trading Post here. I'm interested in making a woods work saw with it. Does anyone have conservative porting #s and any other tips. I intend to start by removing the base gasket, then degreeing the saw and starting from there. I've read about raising the exhaust port 1mm and trimming 1mm from the skirt of the piston on the intake side. Comments?

 

[klickitatsacket]

skip raising the exhaust port and just widen it. This will give more torque than RPM.

 

[SmokinDodge]

skip raising the exhaust port and just widen it. This will give more torque than RPM.

How far do you have widen it to have a noticeable gain?

 

[blsnelling]

I think torque is probably more important to me on a work saw than more RPMs. I didn't realize I could lower the piston top on the exhaust side, since you can't relocate the ring. But as I think about it, the sooner the top of the piston clears the exhaust opening, the more free it will flow and you don't loose any compression this way. How thin can you safely go from the top of the piston to the groove? I don't have the saw yet to give you a measurement.

 

[blsnelling]

skip raising the exhaust port and just widen it

Even when removing the base gasket?

 

[klickitatsacket]

First take the piston and put it in the cylinder making sure it is lined up right. Then take a sharp pencil andtrace the exhaust port onto the skirt. This will show you how far you can take the edges of the exhaust port. DO NOT GO PAST THE EDGES OF THE SKIRT!!! I like to leave at least .020 - .040 on either side.

Even when you remove the base gasket you should not touch the roof of the exhaust port if you are looking for torque. The longer the push the more torque you will develope in your saw. If you want a little RPM to go alng with the it then you can raise the roof a little. I very seldom do though as I like torque and prefer to tune the using sprockets and raker highth.

 

[PES+]

I shall step away To much confusion. Follow his instructions.
opcorn:

 

[blsnelling]

First take the piston and put it in the cylinder making sure it is lined up right. Then take a sharp pencil andtrace the exhaust port onto the skirt. This will show you how far you can take the edges of the exhaust port. DO NOT GO PAST THE EDGES OF THE SKIRT!!! I like to leave at least .020 - .040 on either side.

In other words, widen the exhaust port so that the opening ends .020 - .040 before the edge of the skirt?

Even when you remove the base gasket you should not touch the roof of the exhaust port if you are looking for torque. The longer the push the more torque you will develope in your saw. If you want a little RPM to go alng with the it then you can raise the roof a little. I very seldom do though as I like torque and prefer to tune the using sprockets and raker highth.

Sounds reasonable to me. Should this still leave me below 200 psi compression?

What's your opinion on taking some off the intake skirt of the piston?

I certainly appreciate you info, considering you do this for a living.

 

[stihl038x2]

Diggin' deep into the archives here !!!!!!!!!!!!! Has anyone got info. w/results on porting a Ms 360 Pro ??
I have one on the bench right now. Here are the #'s I have w/out gasket:
Squish. .018"
Ex. opens 105* Atdc 150* dur.
Int. opens 80* Btdc 160* dur
Trans. open 123* Atdc 114* dur
18* blowdown

Where can these #'s be improved upon ??

Thanks for any input......

Steve

 

[mdavlee]

With machine work raise the exhaust and transfers from where they end up after that to 103,118

 

[tacomatrd98]

Cant really comment on the numbers but I can tell you that my 360 pro lost it's gasket, and I did some mild port cleanup and polishing as well as opening the transfers to the base. No timing alteration, base cut, squish band cut or anything and it has 185 psi and freakin rocks compared to a stock one. Muffler mod consists of two 5/8" id tubes coming out at an angle above the clutch cover.

-AJ

 

[old-cat]

mdavlee said it straight. Get the squish band and base cut, .020" is what I very much prefer. Get enough cut off the base so you can use an oem gasket with squish clearance .018" - .020"
All you need to do with the muffler is port match and open the outlet as far as the baffle, without going any forward from where it is.
It will run SUPER!!

 

[blsnelling]

Wow, this is an oldie. I think I had been a member 8 days!

 

[stihl038x2]

Thanks guys, that's the input I was hoping for. I was pondering tac...98's method (feeling a bit lazy on the machining end), now I have Daves #'s, I am getting "less lazy"

Steve

 

[mdavlee]

Those seem to be close in most of the stihls with dual transfers.

 

[CG Racing]

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