Husqvarna 394xp with Stihl envy.

srcarr52 · Apr 2, 2012

Recently I've built a couple of MS660's and I've noticed that they seem to have great throttle response and a little more forgiving of a power band. After much thought I decided it was due to the exhaust port shape and the large stagger in the transfer ports. I decided to make a 394 with an exhaust port of similar shape and similar stagger in the transfer ports to test my theory. I hope to keep the legendary 394 torque and keep it through more of the power band, maybe it will be less thirsty as well.

Stock port.

Tig welded up and flattened on the belt sander.

Almost finished port, I had to weld the holes from the inside of the port, with my old school sine wave tig I couldn't fill in those spots when welding from the outside. It's almost 0.2" taller without hitting the bottom of the exhaust port.

Difference at the muffler.

This saw will have similar port numbers to my best 394's of the past but I've recently started cutting the squish band instead of doing pop-ups.

0.030" off squish band.

bryanr2 · Apr 2, 2012

opcorn:

srcarr52 · Apr 2, 2012

More pictures

Finished exhaust from the inside.

Finished intake port.

The right side transfer port.

And finally... the finished exhaust port from the outside.

I got some videos of it compared to another 394 of similar port numbers with a pop-up and standard widened enlarged within reason ports. I'll post them after I'm done compiling the results and loading the videos.

Jacob J. · Apr 3, 2012

That's an interesting idea.

deye223 · Apr 3, 2012

opcorn:

little possum · Apr 3, 2012

opcorn:

srcarr52 · Apr 3, 2012

Jacob J. said:
That's an interesting idea.

I've never been afraid to pull the tig torch out and start welding on things. If you want more room to cut... add more material. :hmm3grin2orange:

I'm usually welding on things often enough at the race shop the tig torch doesn't get rolled up unless it's time to sweep the floors. This stuff is easy to weld on compared to some of the things I had to do when I was younger and working at an engine shop. A neighboring business was always bringing in lines for custom air conditioning installation into street rods, welding the tiny fittings with a sine wave tig while trying not to melt the rubber hose 2" away from the weld was always a chore.

I tried an expansion step last year and it was slightly successful, this idea seemed way more promising. After cutting 0.030" out of the squish band and dropping the jug down to suit the piston is basically an expansion step anyway.

The exhaust port is almost as flat on the top as a Stihl 066 but it's also a bit wider because you can with the 394 piston skirt width. It's slightly taller than a 066 at the exit but the 394 is a bigger bore so it's proportional. I didn't go full out Stihl style with the exhaust duration, this one is sitting at 159 deg were an 066 starts about 168 deg.

The transfers have 0.030" of stagger from exhaust to intake side where most Stihls I've seen start at 0.045" and 19 deg of blowdown.

tommyus4 · Apr 3, 2012

deye223 said:
opcorn:

My new goal in life is to sit in the row in front of you. Getting tired of these bleacher seats...

Jacob J. · Apr 3, 2012

srcarr52 said:
I've never been afraid to pull the tig torch out and start welding on things. If you want more room to cut... add more material. :hmm3grin2orange:

I'm usually welding on things often enough at the race shop the tig torch doesn't get rolled up unless it's time to sweep the floors. This stuff is easy to weld on compared to some of the things I had to do when I was younger and working at an engine shop. A neighboring business was always bringing in lines for custom air conditioning installation into street rods, welding the tiny fittings with a sine wave tig while trying not to melt the rubber hose 2" away from the weld was always a chore.

I tried an expansion step last year and it was slightly successful, this idea seemed way more promising. After cutting 0.030" out of the squish band and dropping the jug down to suit the piston is basically an expansion step anyway.

The exhaust port is almost as flat on the top as a Stihl 066 but it's also a bit wider because you can with the 394 piston skirt width. It's slightly taller than a 066 at the exit but the 394 is a bigger bore so it's proportional. I didn't go full out Stihl style with the exhaust duration, this one is sitting at 159 deg were an 066 starts about 168 deg.

The transfers have 0.030" of stagger from exhaust to intake side where most Stihls I've seen start at 0.045" and 19 deg of blowdown.

From what I can see, I think you've got a winner there. I tried the expansion step once and didn't notice a difference, but that may have been due to my
un-scientific testing methods. For me it was always more about shaping in relation to how fast a port would scavenge.

One of the best running 066s I ever had was built by Woods Logging Supply in Longview. What that builder did was pretty much make all the ports "square" in
shape where they met the cylinder wall. He took about .010" out of the squish band and dropped the jug down but retained the stock base gasket.

srcarr52 · Apr 3, 2012

The cut times were almost identical to my previously built 394 but you can tell that the raised port saw is much better at recovering and I may be pushing on it a little harder then I should. I think I would see more of a difference in larger wood but right now it's a coin toss. The raised port saw also has a distinguishable sound to it.

Pop-up with standard porting.
[video=youtube;XHtvuOYrghA]http://www.youtube.com/watch?v=XHtvuOYrghA&context=C4345a2bADvjVQa1PpcFN8H830fNw7mbIDycvENT9HrxjP22HPMQE=[/video]

srcarr52 · Apr 3, 2012

Raised port with cut squishband.
[video=youtube;uOgBLD6LdMA]http://www.youtube.com/watch?v=uOgBLD6LdMA&context=C4bb2c9cADvjVQa1PpcFN8H830fNw7mRc-6pgdqc_krMjYBIVRMfw=[/video]

Jacob J. · Apr 3, 2012

I really liked the sound of the welded and raised exhaust 390 compared to the one with the pop-up and standard porting. Both were strong saws for sure
but the welded exhaust saw as you say seemed to take a little pushing in the cut.

Both of them smoked your 2100 and 655 though. Good show.

srcarr52 · Apr 3, 2012

Jacob J. said:
I really liked the sound of the welded and raised exhaust 390 compared to the one with the pop-up and standard porting. Both were strong saws for sure
but the welded exhaust saw as you say seemed to take a little pushing in the cut.

Both of them smoked your 2100 and 655 though. Good show.

I like the sound of it too, it doesn't miss a beat in the cut. I will be doing the same to another one of my personal 394's soon.

Yes, they didn't stand a chance, but the 2100 might get some mild work soon. I could see myself using the 2100 since IMO they are a very well engineered saw.

jnl502 · Apr 3, 2012

Very nice!...Both run good but the welded/raised one did look/sound just a bit better than the other one. Nice work on both though they both ran great. And thanks for shareing your info with us. I think I will have to do some work to my 394xp now.
jnl

NORMZILLA44 · Apr 4, 2012

srcarr52 said:
Raised port with cut squishband.
[video=youtube;uOgBLD6LdMA]http://www.youtube.com/watch?v=uOgBLD6LdMA&context=C4bb2c9cADvjVQa1PpcFN8H830fNw7mRc-6pgdqc_krMjYBIVRMfw=[/video]

Okay you got my attention! You know I love muscle saws, Husky and Stihl. Those 394's you got are sweet, wood eating machines. Awesome! The rakers hungry a little? Just asking mild stalling, which normal no worries. Alot of guys like hungry rakers, your's may no be just curious. Awesome saws though I am impressed:msp_thumbsup:

srcarr52 · Apr 4, 2012

NORMZILLA44 said:
Okay you got my attention! You know I love muscle saws, Husky and Stihl. Those 394's you got are sweet, wood eating machines. Awesome! The rakers hungry a little? Just asking mild stalling, which normal no worries. Alot of guys like hungry rakers, your's may no be just curious. Awesome saws though I am impressed:msp_thumbsup:

Fresh off the roll Stihl RSLK (square ground, classic cutter). It's probably the most aggressive straight off the roll chain you can buy but you can't see the face I'm making trying to push hard enough to put a load on the saw. I did about 15 cuts and I was beat. If I were to run this b/c on a 394 all the time I would lower them a little so I wouldn't be so tempted to push that hard.

mweba · Apr 4, 2012

While running your 394's, many things crossed my mind but a narrow power band wasn't one of them :rock:

srcarr52 · Apr 4, 2012

mweba said:
While running your 394's, many things crossed my mind but a narrow power band wasn't one of them

Thanks, I think I'm getting these 394's dialed in.

What was crossing you mind was probably more like, "What am I willing to trade for one." Really, how is your Dolmar 7900 plan working, or are you wanting to drink the orange cool-aid again?

mweba · Apr 4, 2012

srcarr52 said:
Thanks, I think I'm getting these 394's dialed in.

What was crossing you mind was probably more like, "What am I willing to trade for one." Really, how is your Dolmar 7900 plan working, or are you wanting to drink the orange cool-aid again?

Dolly is all I need and still stock. Was thinking, well I better start building a new one, someone has to dethrone this thing:hmm3grin2orange::hmm3grin2orange:

srcarr52 · Apr 4, 2012

mweba said:
Dolly is all I need and still stock. Was thinking, well I better start building a new one, someone has to dethrone this thing:hmm3grin2orange::hmm3grin2orange:

Watch Out! Complacency is a sign of old age.

oke: Time to shake things up a bit, I think.

Husqvarna 394xp with Stihl envy.

Help Support Arborist Forum:

We can't stop here, this is bat country.

Addicted to ArboristSite

We can't stop here, this is bat country.

Tree Freak

Addicted to ArboristSite

Crash and Burn

We can't stop here, this is bat country.

ArboristSite Operative

Tree Freak

We can't stop here, this is bat country.

We can't stop here, this is bat country.

Tree Freak

We can't stop here, this is bat country.

ArboristSite Operative

Addicted to ArboristSite

We can't stop here, this is bat country.

Addicted to ArboristSite

We can't stop here, this is bat country.

Addicted to ArboristSite

We can't stop here, this is bat country.

Similar threads

Join the conversation!

Join today and get all the highlights of this community direct to your inbox. It's FREE!