Cylinder port question

[lucky]

I have noticed the factory jugs seem to have casting imperfections in the intake and exhaust ports. Is it a good idea to remove these? A while back I read at Madsens that they would clean up the imperfections in the cylinder ports as part of the madsens powertuned procedure. The reason for the question is that I am changing out the crank in a used 044 and noticed the flaws mostly in the intake port. This is going to be a using or woods saw not a race job so I'm not looking for any secrets however I would like to know if these saws can benefit from a light clean-up. Thanks, Lucky

 

[Jacob J.]

Your saw isn't going to benefit unless you really scarf those ports out. There's a lot of meat in there that can be taken out. A light clean-up won't buy you any extra performance.

 

[xander9727]

Don't just get busy with a carbide burr. There is a right way and a wrong way to change the port timing. If you aren't familiar with this, send it to one of the saw tuners on the site and have them perform the work.

 

[xander9727]

Rocky,
I was just providing additional info to prevent any overconfidence that may occur from the previous post.

I agree, nothing bad will happen from removing casting imperfections.

As long as the filings aren't left in the engine.

 

[lucky]

Rocky pretty much said it. I don't want to hog out the port for fear of making the saw "peaky" and losing torque at the cutting rpm. besides this is not new saw and probably not worthy candidate to heavily modify.
I occasionally dig through old posts and look elsewhere on the net to learn more. It seems as though raising the ports makes more horsepower at a higher rpm at the expense of torque I am correct? If this is true then how can you increase torque at the cutting rpm? lower the ports? Or do you need a longer stroke and reduced intake runner volume to speed air flow such as in a four stroke gas motor?

 

[NevadaWalrus]

What's being talked about is really just a phase of blueprinting an engine. Bringing the engine to proper, original, intended specs. If the entire engine is blueprinted and balancing thown in as well, depending on how many things were out of perfection a lot can actually be gained in both performance and durability.

This is true with all engines. In the old days of NASCAR when the cars were really stock, balancing and blueprinting an engine the best as possible is what set apart the winners from losers.

 

[Jacob J.]

Removing those fine casting imperfections is a waste of time. You're talking about imperfections that maybe hinder about .07% airflow, if that much. The only reason to do it is if you're losing sleep at night because every port isn't "shiny" and perfectly-shaped.

 

[lucky]

Your probably right Jacob. The imperfections are small. If it wouldn't gain much power then is the madsens power-tuned saw not much better than a bone stock saw?

 

[Jacob J.]

Madsen's does a lot of work on "Power tuned" saws that I don't agree with. Mostly what they do is modify the piston, removing part of the intake skirt and knife edging the entire piston skirt and sometimes beveling the crown where it meets to exhaust port. In effect they're changing port timing by changing the piston rather than modifying the ports. You can run into trouble with this later on in the saw's life however, I've been inside of several Madsen's powertuned saws, mostly 372s, 385s, and 066s. All of them had trouble with idling and low speed rpm as the saw aged because of the modifications on the pistons. They don't make any changes to mufflers or carburetion either, so there's a still a lot of untapped potential in the engine.

One thing you might consider doing however, if you have your cylinder off, is polishing the exhaust port by hand with different grades of emery cloth and WD-40 or cutting oil. This will lessen carbon build-up. I've heard of enthusiastic builders polishing combustion chambers as well, but I think that's a little more than what a saw engine really needs.

 

[bwalker]

Polishing ports and cleaning up minute inperfections is a big waste of time and will net you next to nothing(or nothing) with a modern saw. Is a minute flaw really relivent when you have a crank whipping around at 13,500 rpm, disturbing flow in the process?

 

[ccicora]

Smoothing out the ports is one way to free up some avalible power in the saw. The 044's have a problem in the top of the transfere towards the outlet of the transfere. This casting mark is very hard to remove but has the potential to block considerable flow on some jugs. Another area to look at is with the muffler on but the front cover off put your finger in the exhaust port and slide it out. Sometime the port on the jug does not line up correctly with the muffler port. By matching the ports you can improve some more flow charateristics. DOn't forget to completely clean in and around any area you do work in.
Good luck, the only way to learn is to try it.

Chris

PS Make sure saw goes Rinnnggaaadddiiiinnggg after your work.

 

[stihltech]

porting

Every little bit helps AND you have to start somewhere.
Polish them ports up real nice and see what YOU think.
I have an operator that polishes his exhaust port and matches the muffler and gasket on every saw. Yes, they do run better.

 

[064 stihl]

When porting a saw, do you polish the intake and transfers too? Or do you leave them with a rough texture to break the fuel and air up?

 

[Tony Snyder]

I would like to see the considered opinion of KD on this.

 

[Jacob J.]

There's two schools of thought in chainsaw engines regarding polished intake and transfer ports-

1.- leave them rough for swirling effect and mixing.

2.- polish them completely because a rough finish will cause the fuel and oil to want to separate.

I've done both, and here's the real deal:

When finishing an intake port and transfer ports it's best to sand them fairly smooth but still leave a little bit of texture. When finishing an exhaust port it's best to polish it. A polished piston crown is also beneficial for reduced carbon build-up. Husky 2100 pistons came brand new out of the box with a polished piston crown.
I have woods saws that I've built myself that way and run them for almost 500 hours. That's a testament to trial and error.

 

[064 stihl]

Yeah, some people say to leave it rough and some say polish. Just wondeing.

 

[064 stihl]

What about race saws?

 

[bwalker]

Do a little reading on unsteady gas flow and ductal flow. You will find that polishing is of no value in regards to air flow in a working two cycle motor. Besides with a two cycle bulk flow is rarely a issue, its the timing of port opening and closing that increase power.

 

[Jacob J.]

I agree- with 35% of your fuel-oil mix spitting back out of a working saw unburned, a little polishing seems unlikely to make a big difference. I think race saws do well with about the same treatment, I've never seen a race jug with a polished intake, but have seen several with polished exhausts.

 

[sedanman]

Not far from my house is the shop of an airflow guru. John Satterfield is sought after by nascar teams for his knowlwdge. I have seen some of his stuff....down right ugly to look at, flows more air than anything! He is the guy to go to for clinder head work, sheet metal intakes and blueprinted carbs. My point?............air don't care about looks. Sometimes a little ripple keeps the airstream turbulent thus keeping dropleats from falling out of suspension. Exhaust is another matter