First Woods Port Attempt - Husky 372

JohnnyBoy1986 · Feb 3, 2010

Ok, i've been reading A LOT up on this and I think i am ready to attempt my first woods ported saw. I have a junk 372 cylinder laying around so i think i'll take pics of it when im finished and let yall see em before i go ahead and attempt the real thing on my good cylinder. any advice before i attempt this on the real jug? also the only question i have so far is should i port match the muffler to it when i am finished?

mdavlee · Feb 3, 2010

You might as well port match the muffler if you're going to do all that other work to it.

JohnnyBoy1986 · Feb 3, 2010

good to know, figured as much.
also do i take .075 - .100 towards the piston skirt horizontally? <-> (i would imagine so) and do i take .075 on EACH side of is that a measurement total? For one more i've heard different opinions on raising the exhaust port the thickness of the cylinder gasket... so should i or not? lol

mdavlee · Feb 3, 2010

I leave the exhaust roof alone. You could just take what you need to get it back to stock timing when you remove the gasket. You want to widen the ports out to about .100 less than the piston skirt width.

JohnnyBoy1986 · Feb 3, 2010

understood, i'll upload pics as soon as i can and get some feedback. thanks so much. any other oppinions are appreciated

AUSSIE1 · Feb 3, 2010

When you go wide, do so a little at a time and check as it is easy to go too far.
Make sure your exhaust roof has a slight arch and lightly bevel the freshly cut edges.

Evan · Feb 3, 2010

i dont measure anything im not that smart. i just widen to the witness lines that the piston sqirt makes on the cylinder wall. then call it good ounce im good and close to it. this is harder to do if the piston has wings on the sqirt. the 372 doesnt have wings

heres a good pick of the witness lines on my 066. this makes it very easy widen and you know where to stop.

wigglesworth · Feb 3, 2010

Evan said:
i dont measure anything im not that smart. i just widen to the witness lines that the piston sqirt makes on the cylinder wall. then call it good ounce im good and close to it. this is harder to do if the piston has wings on the sqirt. the 372 doesnt have wings

heres a good pick of the witness lines on my 066. this makes it very easy widen and you know where to stop.

That is good advice Evan. You can tell on most used cylinder's where the piston skirt rides on the intake and exhaust side. Another note, dont forget to check the location of your ring end pin's.

JohnnyBoy1986 · Feb 4, 2010

thanks to all, i bought some new dremel stuff so we'll give it a go and then i'll post pics asap.

JohnnyBoy1986 · Feb 5, 2010

well i tried on one junker and i dont think i did too hot. any advice on what tools you should use to port? if i can use the dremel, what stones/cutters/or sanders should i use? thanks.

mdavlee · Feb 5, 2010

I use the little round straight barrel looking cutters for most of the porting on the intake and exhaust. I use the real long thin one that is the size of a drill bit for the lower transfer work. I use the little green wheel for upper transfer work. If you want I can get pictures or the numbers off of some of them for you.

Cliff R · Feb 5, 2010

Tricky stuff this porting of 2 stroke engines. Widening ports within the limits of the piston increases cross-section and the ability to move more air. It also kills velocity some. Working on the floors and roofs messes with the port timing, much like doing a cam timing or cam swap in a 4 stroke engine. Keep in mind that raising the roof of the exhaust reduces squeeze some, even though it will allow a few more degrees of scavening time.

Since the piston distance from the case doesn't change, you can move the jug closer to the case and get away with removing some material from the port roof.

Porting doesn't always guarentee a performance improvement anyplace, and some folks never do enough accurate testing before and after the work to know anyhow? That's why I love to watch Brad's video's, with direct comparisons to various modifications with timed cuts before and after to show the improvements......Cliff

JohnnyBoy1986 · Feb 5, 2010

pictures or some of these dremel tools used for the original "cutting" (or grinding) if you will would be most helpful. I had started with a 7/32 straight stone like that which would be used to sharpen 3/8 72LP chain. It works but is veeeery slow. I ported a small 141 husqvarna today at the shop, being that it was a cheap saw and i had a backup cylinder incase, it seemed to work fine. that material was also much lighter and easy to work with. i've seen pics in other threads, the original exhaust port in a 372 slants to the right a bit, when i am finished, should it be slanted still, a little straighter or almost completely straight out?
This is the thread i most read up on -- http://www.arboristsite.com/showthread.php?t=86154

mdavlee · Feb 5, 2010

The number for the bits I use are 116 and 561. One is short a about 1/4" and the other is long and 1/8". I use the small and large sandpaper wheels to polish the ports when I'm done with the other bits. These pictures came from my 372. I worked the transfers today. I just widened the intake and exhaust the first time.
Intake

transfers

JohnnyBoy1986 · Feb 5, 2010

Well after looking at some pics and comparing two cylinders i dont think i did so bad after all, but heres what i've got so far... Im welcoming any comments or any advice yall can give. Thanks

mdavlee · Feb 5, 2010

That looks pretty good to me. You going to work on the transfers any or just leave them alone?

JohnnyBoy1986 · Feb 5, 2010

since i am just starting out i think i am going to leave well enough alone with the transfers. I think im just going to polish my intake port as well, im not so sure im comfortable tackling it yet lol. these cylinders carry no stress, they are trash and simply models for me to make sure i do things right.

AUSSIE1 · Feb 5, 2010

Your exhaust flange where it meets the muffler can be opened up heaps more.
Half way between the threads and where it is now. You can go a little higher and lower. Keep the floor, roof and walls as a straight shot to the cyl. The sides at the cyl don't have to bo a full arch, they can be straight with curvature in the corners and an arch along the roof.
With the lower transfers I like to blend them in to the cases. If you use the base gasket as a reference, you will see.
The general consensus is leave the transfer divider alone.
Don't polish inlet ports.

Evan · Feb 5, 2010

aussie

i dont worry much about the muffler end of things. i wden from the cylinder wall out maken sure the the muffler end is alittle bigger then at the cylinder. you could be 2"s bigger at the muffler and it might not be any better then straight wall out to muffler

i cant remeber how much material there is on the 372 untill youd grind into the muffler mounting bolt threads but on my 066 i got pretty close and wasnt even trying work my way from the cylinder wall out then when i bolted the muffler on to port match i dang near was port matching the bolt head.

joesawer · Feb 5, 2010

When you are working on the ports think air flow, air flow, and air flow. Then think about what sharp edges, shear and turbulence do to air flow. Your exhaust port is short so look at some venturi and get the idea of how it helps the air flow.
Don't worry to much about the intake runner size and polish on a 372 until you get quite a bite farther into the porting game.
In fact a big cc intake runner is harder to tune and tends to move the power band up.
There are huge gains to be had from a 372 with out a lot of complicated work. But you definitely need to get a grasp on timing your ports.

First Woods Port Attempt - Husky 372

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