Ported Husqvarna 372xpw

[Chainsaw Jim]

I got bored and decided to give my 372xpw some serious breathing treatment. I matched the bottom of the transfers to the bottom edge of the ring lands and decided to add fingers (bridge port) to the transfers instead of widening them. I gave the piston a little trim too. Here's a few pics of the progress...

Surprisingly it cuts pretty good set up like this. I know it looks funny as **** with that filter, I don't have a green weenie for it yet.

 

[CapitaineHaddoc]

First time I see finger ports in a 4 transferts cylinder, looks weird.

Do you have some vids of the saw?

 

[gunnusmc03]

 

[Big_Wood]

you successfully ruined that saw. the intake looks so wide it's silly. the intake is likely constantly open to WAY to hogged out transfers on the sides with that piston as well because of that. if you didn't care and were just screwing around it's ok though. LOL

EDIT: after looking at the pic with piston in bore it appears you did have room to go that wide on the intake. you maxed her right out LOL still some scary **** though. i'm interested to see how it runs.

 

[gunnusmc03]

I got bored and decided to give my 372xpw some serious breathing treatment. Here's a few pics of the progress. I matched the bottom of the transfers to the bottom edge of the ring lands and decided to add fingers to the transfer ports instead of widening them. I gave the piston a little trim too. Here's a few pics of the progress... View attachment 440033 View attachment 440034 View attachment 440035 View attachment 440036 View attachment 440037 View attachment 440038

Surprisingly it cuts pretty good set up like this. I know it looks funny as **** with that filter, I don't have a green weenie for it yet.

Quoting for posterity.

 

[bryanr2]

 

[Chainsaw Jim]

you successfully ruined that saw. the intake looks so wide it's silly. the intake is likely constantly open to WAY to hogged out transfers on the sides with that piston as well because of that. if you didn't care and were just screwing around it's ok though. LOL

Of course it was for fun. But the transfers function the same as they did, but with more flow. I didn't drop the intake floor, nor did I remove any front and back on the piston, so I don't know why it would stay open.

 

[Chainsaw Jim]

I apologize for taking so long to upload the video. I've been interrupted with company.

 

[CapitaineHaddoc]

I apologize for taking so long to upload the video. I've been interrupted with company.

This saw seems to be a good runner after all.

 

[Chainsaw Jim]

This saw seems to be a good runner after all.

Yeah, I was thinking it cut ok. It's the first cuts with new rings, so I'm wondering what it'll be like after break in.

 

[drf255]

Those would be bridge, not finger ports. Bridges go across the plated area between the upper and lower transfers. Fingers go from the lower transfers directly into the cylinder wall.

You almost created an open transfer port motor. I've never seen bridges or fingers on a quad either. I believe the thought is that there's already plenty of transfer area.

Work looks clean, but without increasing compression by a popup or squish cut, and without timing it and adjusting the ports, I think you left some most power in the motor. I'd also be a bit worried that all the metal you removed increased the case volume and lowered case pressure.

Did you modify the muffler?

Darn thing runs pretty well though, I must say.

 

[Chainsaw Jim]

Those would be bridge, not finger ports. Bridges go across the plated area between the upper and lower transfers. Fingers go from the lower transfers directly into the cylinder wall.

You almost created an open transfer port motor. I've never seen bridges or fingers on a quad either. I believe the thought is that there's already plenty of transfer area.

Work looks clean, but without increasing compression by a popup or squish cut, and without timing it and adjusting the ports, I think you left some most power in the motor. I'd also be a bit worried that all the metal you removed increased the case volume and lowered case pressure.

Did you modify the muffler?

Darn thing runs pretty well though, I must say.

Thanks for correcting me on the improper terminology. It is a bridge port very similar to mastermind's bridge port work on a closed port Stihl saw from a thread here somewhere, which is where I got that particular idea.
The 372 is actually an open port saw to begin with. I've basically turned it into a morph between open and closed port. This does open up the volume a tad so I threw a 394xp carb on it. Another idea I have is to see if the crank stuffer cups from a 576xp will fit this crank.
If you think it has plenty of power to gain then imagine the difference if I hadn't accidentally free ported the exhaust by about an eighth inch. I was so annoyed when my burr took a quick dive on me to cause that.

 

[drf255]

Most importantly, you're experimenting and having fun. What it's all about.

Yeah, I just did an 036 that I messed up a bit. Lowered the jug too much and I'm freeporting the exhaust at TDC about .020. Wanna lower the jug a drop more, but now can't.

You no longer have the option of lowering the jug either.

Most of the pros here say a little freeporting won't hurt the saw at all. Yours may be proof of that. It runs awesome.

Any idle issues?

 

[Chainsaw Jim]

Most importantly, you're experimenting and having fun. What it's all about.

Yeah, I just did an 036 that I messed up a bit. Lowered the jug too much and I'm freeporting the exhaust at TDC about .020. Wanna lower the jug a drop more, but now can't.

You no longer have the option of lowering the jug either.

Most of the pros here say a little freeporting won't hurt the saw at all. Yours may be proof of that. It runs awesome.

Any idle issues?

Thanks.
I was only disappointed that it was an accident. There are builders who believe in free porting as you say, though I wouldn't be doing it as normal practice. I did do a free port on an ms170 and it turned that saw into a little monster. I regret bringing it up because I never recorded a video.
It does idle perfectly and it responds to tuning like normal.

 

[Mattyo]

If you want to lower the jug you can always machine the chassis...instead of cutting squish band or the base of the cylinder or popup



Machining is at 10 min mark

 

[drf255]

Hes already free porting.

 

[Mattyo]

ah, never mind then...thanks

figured i'd just give another way to do the machining


honestly, i think the saw runs good according to the vid, but i wouldn't have done this to an OEM cylinder. a $40 farmertech maybe... but not an oem piece. and it doesn't look like the transfers were adjusted for timing either.

as long as he's havin fun....

 

[wcorey]

The 372 is actually an open port saw to begin with. I've basically turned it into a morph between open and closed port.

I don't understand what you mean here.
How do you figure that the 372 is open port? And if that were so, how is it you've added "closed port-ness" to it?

Whether the lowers bottom or side feed has nothing to do with being open or closed, if that's where this is coming from...

 

[HuskStihl]

I would think that would slow the flow thru the transfers and take some of the "snappiness" away. The video won't play for me, but I'm hearing it runs nice.

 

[Big_Wood]

I apologize for taking so long to upload the video. I've been interrupted with company.

definitely runs better then i thought it would although no better then a stock saw with that length bar i figure. i bet if you ran a shorter bar it would really shine.