That was a fun pet project with a goal in mind.
Fair warning, the following will probably not be interesting to most people to read. Just saying you’ve been warned.
I needed a new snowblower a couple years ago because the 30 year old Craftsman I inherited from my dad gave up the ghost...
I had two requirements, 1) it be an Airens, and 2) it have the most torque possible without having to go to a different engine format/gearboxes, etc. I wanted to be able to go through any snow conditions encountered in NW Iowa with zero trouble and I wanted to be able to throw snow a looooong way if needed.
Ariens makes basically 4 widths of snowblowers (24, 28, 30, and 32") and offers 7 different engines on various models ranging from 208cc cheapy "homeowner" versions all the way up to the 420cc which is the biggest engine you'll find on any walk-behind production blower. Engine manufacturers don't offer HP ratings anymore, only CCs and torque, btw. Then, Ariens offers their different models in standard or "SHO" configurations. The SHO has a 14" impeller and it also turns about 20% faster which throws snow a hell of a lot farther.
So...what I wanted was the smallest width (30 and 32 are way too big and the difference between a 24 and 28 is one pass on my driveway if you do the math), and the engine with the most torque which = fastest and farthest snow removal. As you might imagine they don't offer it that way. So what I did was ordered a 24" SHO that came with a 369cc engine, took that off without ever starting it and sold it to a guy on Craigslist. Bought a brand new 420cc online for about $200 difference and fabbed the adapter stuff. Then, because I had it all apart anyway, I had a friend machine me a new impeller pulley...
The pulley on the standard machine is X inches in diameter, and to get the faster impeller for the SHO machines they simply decrease the pulley diameter and tighten the tolerance between the impeller and the housing. So I just took it a step further and made another pulley a little bit smaller yet. The stock pulley netted about 1,100 impeller RPMs at 3,600 engine RPM, and when I put the new one on I was at about 1,190-1,200. Doesn't sound like a lot but it's a huge difference.
Last thing I did was dick with the governor arm to speed it up slightly. Almost all Briggs and Chinesium small engines are spec'd to run at a range between 3,500 and 3,700 RPMs. Obviously they come from the factory on the way low end of that, so drilled an intermediate hole in the governor arm and the spring holds the motor right around 3,700-3,750 now. Totally within the duty limits.
So, for about $150 extra (I sold the heated hand grips it came with), I can now easily throw snow over my garage and into the back yard where it doesn't get in my way and it won't melt next to my basement windows. This thing fucking SCREAMS. Goes through even the 30" end of driveway stuff at full walking speed, zero problems. Even though it's a narrower bucket I still get done way faster than before with a wider one. Small width, huge motor, and fast impeller for the win. If your're out there listening Mr. Ariens market research guy, people will buy that shit.