Ported 026 Squish Check

[Mastermind]

Different strokes for different folks.

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Exactly

You'll not hear me say that there is only one way that works.

I've got no stomach for arguing about this stuff either.....

 

[jmssaws]

I never said it's the only way, there's tons of ways and I'm interested in all of them.

I port 066/660's mostly and have done 100's of them and there's simply no way to port one of them to where they will run and have less than 200lbs. The exhaust needs to be a 100 or more and compression is a byproduct of that.

 

[Deets066]

In my 066 I had a guy cut squish for me who didn't fully understand what I wanted. He cut a taper from the cylinder wall to the combustion chamber. It was about .050 taper from the edge to the cc. After that I sent it to Carl to take another .020 out of squish. So now I have a flat but not huge squish band and a .030 taper to the combustion chamber

 

[Andyshine77]

I never said it's the only way, there's tons of ways and I'm interested in all of them.

I port 066/660's mostly and have done 100's of them and there's simply no way to port one of them to where they will run and have less than 200lbs. The exhaust needs to be a 100 or more and compression is a byproduct of that.

Yes the 660 likes some compression. Not every engine is the same.

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[drf255]

I find the discussion fascinating.

 

[Deets066]

How much in each cylinder?

True, 233

 

[jmssaws]

In my 066 I had a guy cut squish for me who didn't fully understand what I wanted. He cut a taper from the cylinder wall to the combustion chamber. It was about .050 taper from the edge to the cc. After that I sent it to Carl to take another .020 out of squish. So now I have a flat but not huge squish band and a .030 taper to the combustion chamber

Seems pretty sporty too.

 

[drf255]

Its extremely hard to eliminate alot of variables to test one cylinder design vs. another on an 026 in particular.

I have one ported with a factory combustion chamber and 200 psi. It runs quite well actually.

It does not have the grunt of the 026 with the flat band and 40 psi more compression. It just doesnt, for real. Same carb, same timing advance, same muff mod.

Its a hell of a lot less work to use the factory chamber.

I plan on experimenting with a tig welded and reshaped combustion chamber to bump compression while maintaining factory piston and squish band geometry.

 

[drf255]

So in essence,

A factory band with a popup dome wound maintain factory geometry and a smaller band with a compression bump.

So now we are entering the popup vs. squish band cut arena.

 

[Mastermind]

The more things change, the more they stay the same.

 

[drf255]

YUP

Exactly where it looked like it was heading.

 

[KG441c]

 

[Mastermind]

YUP

Exactly where it looked like it was heading.

 

[Trx250r180]

If your saw has 175 psi with a gasket delete ,which is good to me on a worksaw when working on a side hill and shutting it on and off often ,can't a good runner still be had without head machining or piston pop top ?

 

[jmssaws]

There's saws around me earning every day that are completely stock and put as much timber on the ground as a ported one, but that's not what it's about to me.

 

[Red97]

Wow. Now that I take a closer look at that, it doesn't look like that cylinder has a combustion chamber, rather just a pocket for the spark plug. "You've come a long ways, baby!"

It is all chamber + the plug pocket. Just a taper from the edge to the plug, you can see the factory shaper tool marks in the chamber. Looks like about 3* with no "squish band".

 

[Stihlofadeal64]

I find the discussion fascinating.

I appreciate it as well. The honest caution of these porters has gained more of my respect.
In teaching my sons about life I've always told them to spare your words before the challenge, and do your talking after the "doing is done"
I believe I sense that here. Thanks guys for being candid without being cocky, and for sharing what you know with us.

 

[SquareFile]

Wide band, narrow band. Domed, arced. I know which one I prefer. Carry on.

 

[Red97]

Now all I have to do is figure out how to hold er down

But as far as compression, I have yet to get over 190, curious to see what 210+ does on the next couple.

 

[angelo c]

The squish band must be tapered because the intent is to create a constant gas velocity, and the diameter at the outside is greater than the diameter at the edge of the combustion chamber. If you try to squeeze the gas from the outside through a smaller aperture then the velocity, pressure and temperatures must increase. Therefore the height of the squish band must increase as you move closer to the combustion chamber to keep the aperture area constant.

The energy that goes into increasing the velocity, pressure and temperature of the gas comes from the fuel and is not converted directly into mechanical energy, so it is waste except to the extent that it might improve combustion efficiencies.

Hey buddy, good to see ya postin. Wishing you warmth and happiness for the holidays.