Poulan 380/3750 -- Stihl 039/390 piston

[Benwa]

The Poulan Pro 380 factory max rpm (listed on the side of the air filter cover) shows 13,800. The Tim Allen 3750 I have shows 13,500. I always found it intriguing and wonder why they felt the need for a higher rpm allowance. They have the same cylinders & same carburetors. Maybe it's a different style muffler that warrants the change or the fact that the Tim Allen comes factory with a 22" bar maybe?

 

[smokey7]

It's very nice to know that there is a higher pin to crown piston available. I believe your workaround for flipping the piston and case matching the jug to the cylinder came out well.

 

[Dub11]

The Poulan Pro 380 factory max rpm (listed on the side of the air filter cover) shows 13,800. The Tim Allen 3750 I have shows 13,500. I always found it intriguing and wonder why they felt the need for a higher rpm allowance. They have the same cylinders & same carburetors. Maybe it's a different style muffler that warrants the change or the fact that the Tim Allen comes factory with a 22" bar maybe?

It's because "Pro" saws are faster like that........

 

[drumbum]

What is the latest on this build?

 

[Benwa]

What is the latest on this build?

Honestly I haven't had it out much since I built it. I feel like it's a strong enough saw. Not crazy, but it's decent enough. I'd like to go back in and raise the upper transfers to get closer to a 20° blowdown. I've done plenty of research, so I just need to work up the courage and relocate the ring locating pin. I'd like the pin to be centered in the intake and just run the upper ring. That way I can widen my ports. It's a good running saw the way it sits, I just never can leave well enough alone. Here's a video just after it was done. No cutting between the 2:30 & 5min. mark so feel free to skip through. Now you got me thinking about it again, I might have to dust it off and tear into it!

 

[drumbum]

Honestly I haven't had it out much since I built it. I feel like it's a strong enough saw. Not crazy, but it's decent enough. I'd like to go back in and raise the upper transfers to get closer to a 20° blowdown. I've done plenty of research, so I just need to work up the courage and relocate the ring locating pin. I'd like the pin to be centered in the intake and just run the upper ring. That way I can widen my ports. It's a good running saw the way it sits, I just never can leave well enough alone. Here's a video just after it was done. No cutting between the 2:30 & 5min. mark so feel free to skip through. Now you got me thinking about it again, I might have to dust it off and tear into it!

Thanks for that!

Do you feel like you produced some gains?

 

[Benwa]

Thanks for that!

Do you feel like you produced some gains?

I think there is still more in it for sure, but Definitely. Mostly from the compression bump from the taller piston. Got rid of an excess of almost .030" worth of squish volume. Saw feels like it has much more torque now. It's pretty happy with a 24" bar on it. For the $35 piston and a little work I feel it was well worth it.