A couple of things. I've heard all the same stuff. My 350's with a hogged out transfer ports have great throttle response. Real snappy little saws, all three of them. So I applaud your effort and hope you enjoy that saw.... and the next , and the next as you start having fun hacking those saws! One thing to consider. Along with increasing the volume of the case & transfer area, I also have increased the intake duration on a variety of builds from the stock 70 degree's btdc to 75 - 78 degrees btdc. 75-76 is best on my builds. The concept was to add more fuel/airmix to help make up for loss of compression due to the increase of crank case volume relative to the swept area of the piston. I've gone as far as 80 but then you get to a point of diminishing returns as the fuel usage goes up.
ALSO tried the 357 intake route. Additional duration on the intake port with stock diameter carburator netted the same type of changes but started easier. My guess is at pull start rpm's, the stock smaller carb ID is an advantage. Just a guess.
Also the upper transfer port area is critical. I had issues with an aftermarket top end... and discovered little tweaks to the transfers where they enter the cylinder can make a big difference both positive and negative. And that is BEFORE changing the top edge to effect blow down numbers.
Compression: Of course you also can adjust the compression with no base gasket on 353/346 and with the 350's you can also remove material from the top of the bearing cap should you need to. I've tried to get the squish around that .020 number using a combination of no base gasket/Three Bond 1194 and removing material from the bearing caps on the 350's.
Muffler mods:. ... guess there are many ways to skin a cat. I added a 2in x 1/2 dia tube on one and a 5/8 on another. The 5/8 ran better so it's what I do.
Exhaust port: For me leaving the top edge alone to maximize how long the pressure is on the piston seems to work best then tweak the transfer ports top edge to get what I was looking for with blow down numbers.
Have a series of video's documenting the trials and tribulations as we stumbled along. AND the learning continues! Had to learn the HARD way on some things.. documented both the good and bad. The last two are ... my bet.. a good representation on how your saw probably runs...
https://www.youtube.com/playlist?list=PLtw-MqiEnI4FqI4p_gjbHg3fsoykcdazS
PS: And to get me in serious trouble, the TWO guys online who gave me the most inspiration to muck around in these things were "mastermind" & "bsnelling" . Combined with years of racing dirtbikes & tweaking those old two strokes..... these chainsaws have filled the gap motorcycles used to have.
