Husqvarna 372 big bore with 064 piston?

[MG porting]

Ok I've built and ported a ton of stihl's but not much of Husqvarna saws Im wounding if anyone who have lots of experience with the 372 big bore with the Stihl 064 piston and if it's worth doing? I've already got a 52mm big bore on my clone 365 and it zips pretty good for the lack of the compression It has which is more because of the massive squish it has over .030 without base gasket I like how it reason to throttle up but I know if I put a 30" bar and chain on it it's going to lack the torque I'm looking for so any one on here that's ever used a 064 piston in the 52mm big bore in the 372xp?

 

[MemphisMechanic]

Run an OEM P&C and make more power than the gimmicky big bore kits.

The B.B. Hyway setups can make good power… if you’re willing to do enough machining and port work to get good squish and good timing numbers out of them.

 

[drf256]

Have you looked into the 272 meteor piston?

It has a higher compression height than the 046 piston and I think higher than the 064 piston as well. It’s 52mm, has a 12mm pin and is quite light. It has .140 of meat above the single ring land. I take .040 off the crown when I use for 044/046 hybrid build and I still need an .040 factory base gasket and .040 out of the 046 cylinder squish band to get to a squish of 20.

The meteor website should have the compression heights of the pistons on it.

 

[Shane¹]

Looks like 064 piston is .5mm taller might help get you closer with squish but now you will either have to cut band or bring cylinder back up

 

[Fun2Cut]

I had a 2717 J-red I played with a bit. Bought the saw worn right out. During rebuild, I put a BB kit in it and played around with it. I’ll say right up front, I don’t have a timing wheel, so take the following with a grain of salt (or less, if you wish.) I ain’t a “saw builder”. My hat’s off to the guys who do it for a profession. Amazing stuff!!

Anyway, I ran an LRB 272 piston in it once I noticed what the squish was. It was around 0.035” W/o the base gasket. With the 272 piston I think I ended up at 0.021” with a doubled BG. Also advanced the timing at the same time.

I was happy with the results. It pulled a 28” with an 8 tooth with decent authority. The 272 piston pin location was simply lower on the piston, so it not only brought my squish to a more desirable position, but also increased intake duration. I’ve since sold the saw. Fellow that bought it loves it. I told him it’s a a/m piston cylinder on it and he was cool with that.

But I haven’t played with a Stihl piston.

Sorry if I’ve detracted from the original intent of this thread.

 

[MG porting]

It all sounds good fellas I might have to invest in a 272 piston now another question do I need to mod the piston to fit the rod end or is the 272 same rod end width?

 

[Czed]

It all sounds good fellas I might have to invest in a 272 piston now another question do I need to mod the piston to fit the rod end or is the 272 same rod end width?

It fits the existing 372 rod and bearing
The 266/268/272 pistons took a shorter
Pin though.
In the last 6 year's I've put together and we've been running 3 of the 372 big bores with 272 pistons and 2 of the 50mm 372s
With 268 popups stumpshot cut them for me.
The positives are they are very easy to start I don't know if it's the less weight/mass of these Pistons compared to the standard 372s
They make decent power but nothing like my zoo city ported 50mm 372s with standard pistons and oem cylinder's.
https://www.arboristsite.com/threads/tearing-into-my-simonized-372xp.275721/
Simonized saws was the first guy i knew doing these mods
They were very popular back then.
He used jonsereds 670 pistons cut down
For the 50mm

 

[Czed]

Not that the 2171/371/372 saws are hard to start but with the 266/268/272 popups they feel like 40/50cc saws pull starting.

 

[MG porting]

It fits the existing 372 rod and bearing
The 266/268/272 pistons took a shorter
Pin though.
In the last 6 year's I've put together and we've been running 3 of the 372 big bores with 272 pistons and 2 of the 50mm 372s
With 268 popups stumpshot cut them for me.
The positives are they are very easy to start I don't know if it's the less weight/mass of these Pistons compared to the standard 372s
They make decent power but nothing like my zoo city ported 50mm 372s with standard pistons and oem cylinder's.
https://www.arboristsite.com/threads/tearing-into-my-simonized-372xp.275721/
Simonized saws was the first guy i knew doing these mods
They were very popular back then.
He used jonsereds 670 pistons cut down
For the 50mm

How are they torque wise do they pull a 30" or 32" strong?

 

[MG porting]

Have you looked into the 272 meteor piston?

It has a higher compression height than the 046 piston and I think higher than the 064 piston as well. It’s 52mm, has a 12mm pin and is quite light. It has .140 of meat above the single ring land. I take .040 off the crown when I use for 044/046 hybrid build and I still need an .040 factory base gasket and .040 out of the 046 cylinder squish band to get to a squish of 20.

The meteor website should have the compression heights of the pistons on it.

Do you think putting the lighter pistons in these saws hurting them torque wise?

 

[Ketchup]

If I remember right the 064 piston needs opened up to fit the little end of the crank on a 372.

Also, both 064 and 272 are windowed pistons. They aren’t designed to feed the lowers on a 372. You can address that by raising the flange on the lowers but that usually results in the Big Bore cylinders warping slightly at the bottom of the bore.

I’ve cut 268/670 pistons to fit 50mm 372 and also fitted a 52mm Hyway 272 piston in a 372BB. I did not find either one satisfactory. You will get more torque out of the original full circle piston with a proper base cut.

 

[Czed]

How are they torque wise do they pull a 30" or 32" strong?

I just used cheap 12.00 ebay cylinders
And maybe ground on the exhaust some
They are good not exceptional to about 24" bar's in hardwood
Definitely not 28+ bar worthy
But then again they are just regular cheap cylinders no porting.
I believe it was @Mastermind who doesn't like these pistons in 372s

 

[MG porting]

I just used cheap 12.00 ebay cylinders
And maybe ground on the exhaust some
They are good not exceptional to about 24" bar's in hardwood
Definitely not 28+ bar worthy
But then again they are just regular cheap cylinders no porting.
I believe it was @Mastermind who doesn't like these pistons in 372s

That's pretty much why I'm asking these questions to better understand before I spend any money on something that might make the saw go backwards in torque gains you know how the old saying goes torque wins races lol I probably won't do the open windowde piston I might buy a few different 52mm big bore pistons for a 372xp and do so comparisons with them to see if any of them have a taller compression high. The big bore kit I've got on the saw now has a single ring piston in it the port timing numbers are not bad other than the exhaust roof is higher than I prefer and cutting the base would lower the intake to much for my liking so if I can fina full circle piston that has just a bit more compression hight I think the saw would be where I want it to be. I really appreciate all the info guys much appreciated so do you guys think beings that there's quite a few different big bore pistons out there that I might find one that could have more compression hight to it?

 

[drf256]

Do you think putting the lighter pistons in these saws hurting them torque wise?

Piston weight has nothing to do with torque.

Ketchup is right though. You are increasing case volume by going with the windowed piston which likely takes up less volume than the non windowed slug.

If you have a bigger bore, the increased case volume may keep the case volume/displacement ratio the same. It might increase torque.

In general, big bores are lack luster. The oem optimized the smaller bore cylinders.

 

[Maintenance Chief]

This is an 18$ bb kit I woods ported. Thats an oak tree that busted one of our fences.

 

[MG porting]

This is an 18$ bb kit I woods ported. Thats an oak tree that busted one of our fences.

I paid $38 for the one I got I ported mine and it's a little bit snapper than yours did you do anything to the ignition timing at all?

 

[Maintenance Chief]

I paid $38 for the one I got I ported mine and it's a little bit snapper than yours did you do anything to the ignition timing at all?

Nothing to the timing, but probably needs it.

 

[MG porting]

Nothing to the timing, but probably needs it.

I went a half a key on mine and I know I could go even further but a half a key is safe for a work saw I bet yours would like a half a key.

 

[Czed]

That's pretty much why I'm asking these questions to better understand before I spend any money on something that might make the saw go backwards in torque gains you know how the old saying goes torque wins races lol I probably won't do the open windowde piston I might buy a few different 52mm big bore pistons for a 372xp and do so comparisons with them to see if any of them have a taller compression high. The big bore kit I've got on the saw now has a single ring piston in it the port timing numbers are not bad other than the exhaust roof is higher than I prefer and cutting the base would lower the intake to much for my liking so if I can fina full circle piston that has just a bit more compression hight I think the saw would be where I want it to be. I really appreciate all the info guys much appreciated so do you guys think beings that there's quite a few different big bore pistons out there that I might find one that could have more compression hight to it?

When i had my oem 372 50mm cylinders ported
By zoo city i bought them for 109.00 each shipped lol
From a place called fixmytoys on ebay
He preferred the 50mm cylinders to port.
The xpw cylinders were the same price back then but it was always kind of difficult to get pistons
For those easily
Now very difficult.
Everyone likes the 268/272/372 saws i have I'm not changing them back.
They made really good firewood saws
Just plain easy to live with
No effort to start them
Compression is in the 180s