Author Topic: 359 WP Timing #'s  (Read 807 times)

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Offline farmboy

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359 WP Timing #'s
« on: May 11, 2012, 09:22:26 am »
Anyone have a set of timing #'s for 359.  Saw is worksaw. 
Shep

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Offline Al Smith

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Re: 359 WP Timing #'s
« Reply #1 on: May 11, 2012, 11:07:48 am »
FWIW timing numbers are completely worthless unless you factor it time area open in reference to RPM's ,cross sectional piston size and several other factors .

Many a well meaning person with all good intents have for example taken a stock saw and raised the ex port a few degrees in hopes of raising the RPM's .It did in fact do that but at the same time lowered the power output .

I'm not trying to be a smart alec about the whole thing just pointing out there's more to it than just numbers on a degree wheel . :)

Offline EHP

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Re: 359 WP Timing #'s
« Reply #2 on: May 11, 2012, 12:36:33 pm »
biggest thing on the 359 is the bottom of the jug on the transfer ports , that huge ledge that blocks off alot of the passage way into the transfer port needs to be ground to allow more air/fuel to pass , 359 is honestly a very good motor and ports well, it makes a good motor cause they do last as they normally donot turn up those real high rpms , sure you can port them to turn those high rpms but in a worksaw that is not needed , a saw that will hold 12,000 rpms in the wood under pressure is all you need and does not get hot and the crank bearings will last

Offline farmboy

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Re: 359 WP Timing #'s
« Reply #3 on: May 11, 2012, 06:58:26 pm »
FWIW timing numbers are completely worthless unless you factor it time area open in reference to RPM's ,cross sectional piston size and several other factors .

Many a well meaning person with all good intents have for example taken a stock saw and raised the ex port a few degrees in hopes of raising the RPM's .It did in fact do that but at the same time lowered the power output .

I'm not trying to be a smart alec about the whole thing just pointing out there's more to it than just numbers on a degree wheel . :)

Agreed Al.  Trying to learn more including use of a degree wheel.  If I have one it correctly
Ex opens 101*
Int opens 78*
Tran opens 120*
BD 23*
EHP Have cut out the ledge and blended into the transfer covers.  Plan on widening I & E to 65%-70% piston diameter.  Cutting windows in piston.  Is there a rule on widening the upper transfer toward the intake?  Ex:  If transfer is 20mm long do you widen by 5mm toward the intake.   No cyl. gasket squish is avg. .032.  Squish band needs cutting/trueing.  Don't have anybody locally to cut the base.  Be gentle on me I'm learning.  Normally just widen I & E polish ex. and put up gasketless w/Threebond 1194.  Got some Loctite 515 I'm using on this one.
Shep

Offline Al Smith

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Re: 359 WP Timing #'s
« Reply #4 on: May 11, 2012, 08:01:08 pm »
If I read that correctly you have 19 degrees of rotation from the ex opening until the transfers open .That would equate to 19 degrees of blow down not 23 .23 would be a lot better though .

You're going to have to put the math to it .You need the extra transfer area for sustained high speed runs .As the speed increase  the time for transfer decreases therefore you need more area and/or more time open . There's a ratio involved related to speed but I can't remember it off the top of my head .

You have to keep in mind a lot of folks use software that pretty well figures this stuff out .I do it the old fashion way with the degree wheel and a port map .--as well as a little blind luck . ;)

Offline Al Smith

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Re: 359 WP Timing #'s
« Reply #5 on: May 11, 2012, 08:08:41 pm »
Here's another point to ponder .A stihl 084 is a large saw  but because the stock operating  speed is around 11 thousand rpm's the relative size of the porting compaired to that giant piston is small .

Conversely a Stihl 020 or 200T is a small saw but stock they run at speeds above 14,000- rpms constainly.The porting size by comparison on those little things is huge .

Offline EHP

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Re: 359 WP Timing #'s
« Reply #6 on: May 11, 2012, 11:23:48 pm »
ok first thing I will tell you is this as I see alot of guys make this mistake , its far easier to find your porting numbers by going from just opening to fully close on you port , so lets do the ext port , bring down your piston until you just see light threw the very top of the ext. port , make this as small as you can, now set your degree wheel at zero, bring the piston down to BDC then back up to where you can just see the smallest amount of light threw the ext port , check your total degrees and divide by 2 , that is your degrees for the port on the ext. way to many guys have to much trouble finding TDC and if your porting off TDC you need to be exact on TDC which lots of guys are not , just being off .010 makes a big difference , next I would think you took the intake port and ext port to find your blow down, blow down is the difference between your ext. port and the transfers .
I see lots of guys cut huge transfer ports towards the intake port and some cut almost over top of the intake port, I do not do this at all , your port can only flow at the narrowest point so why cut a huge hole past that point , you are loosing speed in your income fuel/air charge this way , tht will work better on a pipe motor than a muffler motor cause the pipe will draw your fuel charge threw the port for you

Offline EHP

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Re: 359 WP Timing #'s
« Reply #7 on: May 11, 2012, 11:34:11 pm »
All so remember what works on your 359 will not work on say a stihl 460 or a 7900, you have to treat each different motor design as its one motor and figure out how to make it run , BMEP is this ratio but in most cases the larger the motor the lower you have to make your BMEP cause the higher the BMEP the more heat you are going to create and heat is what tells you if the motor is going to live or die . Also donot get caught up in the computer aids helping you build stuff cause most will let you build a motor that just cannot run or even come close to running  as they will say its ok to raise your transfers to a unreal number , same with the ext port . Your best to take small steps and learn as you go and take notes on what you thought worked and what did not , on a 359 just goes easy on the porting and do the muffler mod and you will be surprised at how well your saw will run , porting is not done by the pounds of metal removed from he motor , some motor you can do quite abit of porting and they work great where others donot like their porting numbers changed alot

Offline Al Smith

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Re: 359 WP Timing #'s
« Reply #8 on: May 12, 2012, 09:30:03 pm »
I could suggest a few things except for  the fact what I know about Husqvarnas would fill a shot glass if all the info of same would fill the Atlantic ocean .Wrong color of orange for me .Now one color of yellow I might be able to do you some good except for all practical purposes McCullochs are just collecters items.

In case nobody ever turned you on to it this link will give you a lot of info .It's basic but it's a start . http://www.chuckbunnell.com/kart/jennings/jennings.html

Also a bike tuner by the name of McDizzey is a good one .RC sites are good as well as British bike sites .You can glean some info on chainsaw sites but it won't be much .Most just want to argue about it .Get what you can and like Ed said go at it a little bit at a time .You'll get it if you hang long enough . ;)

 

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