372 muffler mods

[Bradley]

Well I just got done making some cuts with my 372 after opening up the muffler. A 7/16" by 1 1/6" hole in the support bracket with a screen behind it. This makes all the difference in the world. I couldn't pull the saw out of it's powerband with a 24" bar in a 20" log. It's barely louder than before and revs a whole lot faster when you squeeze the throttle. It is interesting that most of the exhaust comes out of this new opening now and the saw is much quicker to start. I think it's time to buy another saw to play with now. Steve.

 

[Lawrence Martin]

hey bradley

I did the same thing to my 371 about a 6 weeks ago ,

Went to home depot bought a demel cut it with the disk wheel, put an old screen between the muf' and bracket.

then returned the dremel , love the sound ,but it is louder, and power gains are great.

Have fun with the new toy

Play safe!!

lawrence

 

[timbercutter007]

Could someone tell me what the best size and shape of hole to put in the muffler of my 372xp. I was thinking I'll put it through the bracket w/ a screen. This will be the only mod to this saw.

 

[kdhotsaw]

372-385 husky muffler

hello bradley and timbercutter,
sounds like you got the port size right. we also open the top port up a bit because they are all bent down from the factory.also grind the small ledge in front of the top outlet. these modifications will net you a 15-20 % power increase.
Inclosed a photo of our modified 372-385 muffler
ken
[email protected]
530-589-2744

 

[Bradley]

Hi Ken, I used your picture in a previous post along with the help of another poster named Jeff to make the mod. And yes, I did open up the top outlet and smooth it out. There is very little flow out of that top port now from what I can tell. I would think that this fact demonstrates how restrictive the factory port is. Do you think that the carb needs to be adjusted now or anything else. If it does I'll have to get someone else to do it 'cause it ain't a Holley 4-barrel so I need not screw with it! I thought that the new port would make a difference but I didn't know it would be that noticeable. Is this same modification, with different and appropriate port sizing, viable for other Husky's? Thanks, Steve.

 

[HUSKYMAN]

My Walkerized 670 has two 5/8" holes that look like this:






It sounds AWESOME

 

[YUKON 659]

Isn't it a pleasure to have guys like Ken on board who freely give help to us novices.:blob4:

 

[kdhotsaw]

670 jonsered

hello huskyman,
that 670 jonsered and the mods to the muffler look good, like your ready to do some serious cutting. nice photo.
ken

 

[kdhotsaw]

mufflers

hello bradley,
yes you could probably richen it up some, mabey i/8 of a turn out on the high speed needle. the factory has to contend with epa carb tier 1,2,3 and 4 emission requirements so there is a lot of hp to be gained by modifing the mufflers
on other huskys and stihls we use different extra port arrangements, just depends on the saw
enclosed a photo of one of my 394 husky woodcutters, runs good

ken
kdhotsaw

 

[Bradley]

Ken, I will try the carb adjustment tomorrow. Is that port large enough, or do I need to make another or make that one bigger? What about those pipes on the 670? Better? Worse? Unnecessary? Thanks for the info, Steve.

 

[HUSKYMAN]

The one hole you made is probably enough. Dont make your muffler look like swiss cheese
Try and post a picture of it so we can see it. Is the hole 1 1/6" deep or wide? If its that wide you definitely are all set.

 

[kdhotsaw]

muffler mods

hello bradley,
like huskyman says dont make swiss cheese out of it. you can fit two 5/8 pipes if thats what fluffs your skirt. the important thing is not to go to large as power will begin to fall. on one of my o66 stihls a few years back I added a third port figuring it would run better but it didnt so you dont want to go too large. mike rupley(rupedoggy) and I were playing with his 680 solo timing the cuts we were making 5 second cuts in a 16 inch log. when we removed the front cover to the muffler it dropped to 5.5 seconds . the extra port should be the proper size.
if you put an additional port in the front and fit a screen and a deflector you wont pull in any debris and the forest service people wont be hasseling you on government land 2 5/8 pipes work good but they are a tip-off that your saw has been modified
ken
kdhotsaw@ hotmail.com

 

[Bradley]

Huskyman, look at the picture Ken posted on this thread of the 385 muffler and that's what mine looks like. Steve.

 

[timbercutter007]

Thanks to all who shared advice. I'll make the muffler mod. and add a 8 tooth rim in a month or two. I lent my saw to the IN GOL National finalist to train with (he wants it stock). I have one more question, would the muffler mod. cause any durability problems? I don't want to loose my favirote firewood saw (it makes my firewood buddies old McCaullah look so slow like it is.)

 

[kdhotsaw]

muffler mods

hello timbercutter,
opening up the muffler will help on the durability. your reducing the backpressure and helping the saw run cooler. because the saw runs cooler the stihl or husky petroleum based oil stays under the 400 degree tempeture where it begins to break down and form varnish hence durability is increased. going to a high quality 100 5 synthetic oil really helps on the varnish issue.
ken