Husky 570 Crank Stuffers. Keep or Ditch?

[Bjorn]

Hello. With crankstuffers, more vacuum is built on the up stroke, and more crankcase compression on the down stroke.

 

[Brewz]

Yes I understand that is the traditional line of thought.

The whole saw felt like it was geared around trying to make half decent power while being severely emissions restricted.
The small exhaust port, 10 to 12 deg of blowdown and visible signs of burnt gas back feed into the transfers is odd.
Then stuffers to try and push against this harder?

Im doing this to see what the saw does..... Sometimes we need to think outside the square..... Its worked for me before.
My intuition says its going to run well.
It wont ever be a world beater with the little low top filter but I am looking forward to running it beside my ported 371

 

[Stump Shot]

At the end of the day all we can do is go by what our gut tells us to, or as one fella put it to me, "some times you have to fire the engineer and just build the darn thing."
While the 570 was never known as a world beater saw by any stretch of the imagination, I believe at least in part some of that rep came from how smooth the saw cut, it just doesn't feel like it's doing what it actually is. If that makes any sense at all.
I'm very curious to see how this works for you as I have motives in the form of a 575xpg that is in need of a rebuild. Why did I pick up such a saw for myself one might ask with all the others out there? It was my experience with the 570 in stock form that stuck in my mind.
Also noteworthy is the new owner of that 570 has been tickled pink with it and has been cutting firewood ever since without fail.
Here's a vidja I dug from my channel of that saw, take into account this is very soft wood compared to what is in Australia.

 

[Ketchup]

Yes I understand that is the traditional line of thought.

The whole saw felt like it was geared around trying to make half decent power while being severely emissions restricted.
The small exhaust port, 10 to 12 deg of blowdown and visible signs of burnt gas back feed into the transfers is odd.
Then stuffers to try and push against this harder?

Im doing this to see what the saw does..... Sometimes we need to think outside the square..... Its worked for me before.
My intuition says its going to run well.
It wont ever be a world beater with the little low top filter but I am looking forward to running it beside my ported 371

The idea that engineers added features to restrict the saw is completely sound. I’m very interested in your conclusions.

Recently I’ve been wondering if case volume or case compression stage matters more. A lot of my saws end up with increased case volume (improved flow at the lowers) and a wide (and often raised) epoxied intake. It’s seems to be an improvement over leaving the intake where the machine work drops it.

I’m curious how this 570 will perform with longer bars. I don’t totally understand how rich saws clean up in a big cut, but larger case volume may function as a fuel reservoir when the saw has to work harder.

I’m psyched your following your intuition and trying something different.

 

[Brewz]

Muffler done

 

[Brewz]

Runs nice
Might be a while before it sees timber though, we are badly flooded here at the moment.

 

[whitesnake]

Sounds good!

 

[Brewz]

I’m curious how this 570 will perform with longer bars.

It will be wearing a 20" bar, we don't run much more on them here as they tend to struggle a bit in our timber.

Was having a laugh earlier thinking when I run it, I will then wonder how it would go with the stuffers installed haha

 

[drf256]

Runs nice
Might be a while before it sees timber though, we are badly flooded here at the moment.

Gotta work on them legs Tony, a bit too thick for a porter.

We know that the stuffers are there to reduce case volume, and there are known calculations of case/cylinder volume that have been noted to be optimal.

If one has a heavier piston, as in the case of a strato saw, one needs bigger crank counterweights which may make case volume excessively large requiring stuffers to keep that ratio within reason. May be part of why that saw is noted to be so “smooth”.

I believe rule of thumb is more case volume=more torque and less case volume=more rpm. Make sense, because if a saw can flow X volume of air through it, and it can only take smaller gulps, it will need more cycles to move the same volume.

I like this thread. One of the more interesting ones here in a while.

 

[Brewz]

Yes that's all the known and widely followed guidelines, but its all too rigid, "walk between the lines or else" for me.
I think there is more to the dynamics than that.

Time will tell, it may fall on its face, but there was only one way to find out.
At least I know the bearings are getting oil

 

[Ketchup]

It will be wearing a 20" bar, we don't run much more on them here as they tend to struggle a bit in our timber.

Was having a laugh earlier thinking when I run it, I will then wonder how it would go with the stuffers installed haha

Toss a 28” on it and noodle something for science. Or just lean on the 20” extra hard. If it has a low gear you’re on to something. There are a several 5-series saws that I wish had more bottom end power.

 

[Dolkitafreak]

Yes that's all the known and widely followed guidelines, but its all too rigid, "walk between the lines or else" for me.
I think there is more to the dynamics than that.

Time will tell, it may fall on its face, but there was only one way to find out.
At least I know the bearings are getting oil

I like removing the stuffers, I feel they block lube from bearings, and have no issue with increased crankcase capacity typically.

One question I will ask is that since your case volume is now much larger, should intake be dropped in order to fill the large space? Or better to keep it high to really squeeze what does enter?

personally I don’t mind a low intake

 

[Brewz]

Toss a 28” on it and noodle something for science. Or just lean on the 20” extra hard. If it has a low gear you’re on to something. There are a several 5-series saws that I wish had more bottom end power.

I will.
I don’t think it’s just 5 series saws, I think it’s most strato saws that lack the low gear we got to like with older models.

The thing I like about this saw is the smaller bore/longer stroke.
Piston is only 49mm.

In real hard timber this is an advantage.
Saw is not as snappy but holds on better under extreme load in most cases.

It will get load tested.
I have no interest I’m trying to make a saw look better in soft wood, I put a hurt on them to make sure they do what’s needed.

 

[Brewz]

I like removing the stuffers, I feel they block lube from bearings, and have no issue with increased crankcase capacity typically.

One question I will ask is that since your case volume is now much larger, should intake be dropped in order to fill the large space? Or better to keep it high to really squeeze what does enter?

personally I don’t mind a low intake

I tend to like less intake.
I think people lower the intake chasing power, and it may work in sone cases but for how I port a saw, I find less works just fine with my porting.

Remember it’s not just time to be considered.
Area plays a big role in power band and more area can mean less velocity at lower rpm under load.

I find velocity for short time works better than a big lazy hole

 

[Maintenance Chief]

I tend to like less intake.
I think people lower the intake chasing power, and it may work in sone cases but for how I port a saw, I find less works just fine with my porting.

Remember it’s not just time to be considered.
Area plays a big role in power band and more area can mean less velocity at lower rpm under load.

I find velocity for short time works better than a big lazy hole

Thats why Holley made performance 390 and 450 cfm double pumper carburetors.

 

[Bjorn]

Hello. It doesent have to be a big lazy hole in the cylinder, to make longer intake timing.

 

[Bjorn]

Hello, is it still flooded in Australia? Or have you been able to test the saw.

 

[Barn Shop]

Kinda late to this reply, but in late 2020 or early 2021 I built a 576xp non autotune without the stuffers running a 575xp crank and piston (which has holes in the strato cutout that the 576 doesn't) in the OE stock 576xp cylinder, sold the saw to a buddy sporting a 24" .058 Oregon bar and chain, was amazed at how it ran, gobs of power.
In my adolescent wisdom of thinking I believe the stuffers were installed along with the Stratos Charging as a way to meet the EPA Emissions Standards at that time, a smaller area equals a smaller fuel charge which will equal less emissions, also it kinda unshrouds the PTO side bearing for better oiling, But hey what do I know.
What I do know is the saw was easier to tune and was able to open the main jet further than what I was on my stock 575xp, before it started 4 stroking, so in my opinion with the stuffers out there is more volume area to fill equally with air and fuel and that will directly result in a more dense charge into the cylinder resulting in more power. But again what the hell do I know.

 

[Barn Shop]

For science!

I was thinking take this part away if you left the stuffers.

View attachment 342769

But better to try both!

Be VERY CAREFUL, I went too far and ground a hole in the case while doing this.
Not saying it can't be done just go easy.

 

[huskihl]

Kinda late to this reply, but in late 2020 or early 2021 I built a 576xp non autotune without the stuffers running a 575xp crank and piston (which has holes in the strato cutout that the 576 doesn't) in the OE stock 576xp cylinder, sold the saw to a buddy sporting a 24" .058 Oregon bar and chain, was amazed at how it ran, gobs of power.
In my adolescent wisdom of thinking I believe the stuffers were installed along with the Stratos Charging as a way to meet the EPA Emissions Standards at that time, a smaller area equals a smaller fuel charge which will equal less emissions, also it kinda unshrouds the PTO side bearing for better oiling, But hey what do I know.
What I do know is the saw was easier to tune and was able to open the main jet further than what I was on my stock 575xp, before it started 4 stroking, so in my opinion with the stuffers out there is more volume area to fill equally with air and fuel and that will directly result in a more dense charge into the cylinder resulting in more power. But again what the hell do I know.

The idea behind the stuffers is that more case vacuum is built when the piston is on its way up and more pressure is built on the way down before the transfers open. The results are a higher but narrower rpm hp range