Part One: The Exhaust Port

[Fruecrue]

One of my best running Muffler saws Freeports to the point you’d grab a tape measure before a caliper or micrometer to measure it.

Exhaust is high enough to run a pipe on it, but it don’t like the pipe. I’d guess the Freeport has a lot to do with that.

 

[Lightning Performance]

I like turtles?

Damn turtles

 

[Ketchup]

Sometimes you can swap in a piston with a longer skirt.

 

[Lightning Performance]

Sometimes you can swap in a piston with a longer skirt.

Most times they weigh more, penalties must be paid.
You can lighten them but they do like to crack if more then a parting line is taken away or some skirt trimming. Smooth finish work can still fail. Polishing pistons is not how I plan to spend my days or nights. Polishing the exhaust exit area is never a bad thing on the top. Forgetting about the hole under the piston will be much easier imo than worrying about it again.

 

[Eccentric]

I like turtles?

....and rented pigs?

 

[Mastermind]

....and rented pigs?

We don't rent pigs.

 

[jurchybald]

So little free porting and pigs for private use only is ok. Got it

 

[Mastermind]

So little free porting and pigs for private use only is ok. Got it

Pretty much.

 

[merc_man]

We don't rent pigs.

Do you rent turtles?

Sent from my SM-G950W using Tapatalk

 

[Mastermind]

Do you rent turtles?

Sent from my SM-G950W using Tapatalk

Absolutely not.

 

[ZukiRyder400]

So.......we really haven't found any real solid answers to the question. "What port heights should I use?"

OK........what about width?

Shape?

Outlet size?

Finish?

I have been experimenting on a 2159 with different cylinders w/ different port timing. Left one exhaust at 103*, the other at 105.5*. With the exhaust being lower on the second one, I left the intake a little bit higher as well (77*). In my hands there was a drastic increase of the forgiveness and usable power with that second cylinder. So much so that I slapped an 8 pin on to see how it faired. When I went back to cylinder #1 with the higher exhaust, It felt lazy and did not feel good in the cut at all.

 

[Mastermind]

I have been experimenting on a 2159 with different cylinders w/ different port timing. Left one exhaust at 103*, the other at 105.5*. With the exhaust being lower on the second one, I left the intake a little bit higher as well (77*). In my hands there was a drastic increase of the forgiveness and usable power with that second cylinder. So much so that I slapped an 8 pin on to see how it faired. When I went back to cylinder #1 with the higher exhaust, It felt lazy and did not feel good in the cut at all.

I've found the same thing to be true. Good on you for doing the comparison.

 

[huskyboy]

I have been experimenting on a 2159 with different cylinders w/ different port timing. Left one exhaust at 103*, the other at 105.5*. With the exhaust being lower on the second one, I left the intake a little bit higher as well (77*). In my hands there was a drastic increase of the forgiveness and usable power with that second cylinder. So much so that I slapped an 8 pin on to see how it faired. When I went back to cylinder #1 with the higher exhaust, It felt lazy and did not feel good in the cut at all.

Change the intake on the higher exhaust one to 80 and see if that makes any difference. Just curious...

 

[ZukiRyder400]

Change the intake on the higher exhaust one to 80 and see if that makes any difference. Just curious...

That one with the higher exhaust was actually at 81. I know that's pushing it but it was for experimental purposes. Now that I've ran some decent saws I HATE lazy saws, my 357 cylinder being one of them. No machine work, .030" squish, 102.5 on the exhaust and 80.5 deg. on the intake... that was one of the weakest if not the weakest cylinders that I have ever put on a saw. It turned some freaking RPM though(15.5k while slightly 4 stroking), BUT, whats more usable for working conditions, Max RPM or an all around type of saw you know what I mean?

 

[Mastermind]

Change the intake on the higher exhaust one to 80 and see if that makes any difference. Just curious...

It probably would make it even less user friendly on torque. But, it will make it spin up higher, and quicker. For a cant cutter, longer durations make a faster cut. If you can keep from stuffing it.

On a worksaw though, a long intake duration makes more spit back. And soaks the air filter. Then all sorts of oddness occurs.

 

[ZukiRyder400]

I have also been trying different blowdowns too. It seems a shorter one (15*-17*) made that 359 (It could be only this particular saw/cylinder) a little livelier I did this on the lower exhaust cylinder, With the higher exhaust I ran a longer blowdown and it didn't have the torque of the lower one but it picked right back up after i leaned on it or stalled the chain. Im still trying to get a grasp of everything.. I could be talkin crazy too LOL.

 

[ZukiRyder400]

It probably would make it even less user friendly on torque. But, it will make it spin up higher, and quicker. For a cant cutter, longer durations make a faster cut. If you can keep from stuffing it.

On a worksaw though, a long intake duration makes more spit back. And soaks the air filter. Then all sorts of oddness occurs.

I concur Randy, I m at about 82 deg of intake on a Husky 372 X torq and when I stab the throttle, I could see some of the fuel coming back up through the filter holder/ air horn. She doesn't run bad but I have an OE 50mm 372 top end waiting to be ported

 

[Mastermind]

I have also been trying different blowdowns too. It seems a shorter one (15*-17*) made that 359 (It could be only this particular saw/cylinder) a little livelier I did this on the lower exhaust cylinder, With the higher exhaust I ran a longer blowdown and it didn't have the torque of the lower one but it picked right back up after i leaned on it or stalled the chain. Im still trying to get a grasp of everything.. I could be talkin crazy too LOL.

A theory of mine.....and chock full of exceptions.

A two port transfer setup needs less blowdown than a four port arrangement.

I think that it's because the two port deal is lazy....has less velocity. The shorter blowdown gives it a head start on movement.

 

[ZukiRyder400]

2159 that has the lower exhaust cylinder with the shorter BD.

 

[huskyboy]

It probably would make it even less user friendly on torque. But, it will make it spin up higher, and quicker. For a cant cutter, longer durations make a faster cut. If you can keep from stuffing it.

On a worksaw though, a long intake duration makes more spit back. And soaks the air filter. Then all sorts of oddness occurs.

Maybe he could fill the intake? Trying to think of any way he could salvage that cylinder for a worksaw.