Part One: The Exhaust Port

[mdavlee]

Raising some 3/16-1/4" can be a little shaky when you first fire them up

 

[Mastermind]

So.......what about finish?

Super shiny?

Sorta rough?

Why?

 

[Moparmyway]

Here's @huskyboy 044. The port came out a bit square on the roof for my liking. Runs great though.

Your first picture is why I find it best to put the piston in the bore and check the exhaust roof, with the piston near the top of the roof.

So.......what about finish?

Super shiny?

Sorta rough?

Why?

I've done them like a mirror after it was rough ............. didnt notice any difference, except in muh grubby fingers, they hurt a little from holding the handpiece while I was makin a mirror

 

[paragonbuilder]

Raising some 3/16-1/4" can be a little shaky when you first fire them up

What do you mean Mike?


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[huskyboy]

It's got nearly 20 tanks through it and hasn't consumed itself.

It sure runs like a a raped ape

 

[mdavlee]

What do you mean Mike?


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Raising exhaust that far.

 

[mdavlee]

So.......what about finish?

Super shiny?

Sorta rough?

Why?

80 grit is as smooth as I go. I can't find a difference in 80 and 220

 

[Johnmn]

80 grit is as smooth as I go. I can't find a difference in 80 and 220

Agreed only the couple saws I have done just seems like with finer you just use more

 

[XP_Slinger]

I've only ported a couple saws and they were left rough to semi-polished, they run hard.

 

[drf256]

I don't polish at all.

The 044 port is one cone of coarse Craytex that I cleaned the carbon out of the port with. I got that finish quiet easily in under 2 minutes.

I don't see the point in polishing them.

 

[Mastermind]

I used to try to create a certain look. Sorta shiny....

After pulling saws apart a year or two after the port work was done, I realized that polishing the port is a complete waste of time.

But......what about a layer of carbon acting as an insulator?

Is that possible? Would that be a good thing?

 

[mdavlee]

I used to try to create a certain look. Sorta shiny....

After pulling saws apart a year or two after the port work was done, I realized that polishing the port is a complete waste of time.

But......what about a layer of carbon acting as an insulator?

Is that possible? Would that be a good thing?

That can be a good thing. Less heat absorbed the better. 288 rattler Mike did.

 

[huskihl]

I finish with 80 grit emery in a split nail for a mandrel. The oils I've been using leave a black grease on the port that wipes off with your finger. In my 034 above, I wiped it off before the pic, and it smeared on the piston. Makes it look like the piston is varnished or the rings didn't seat. I've found 80 grit to be smooth enough for me

 

[Redfin]

I only sand enough to smooth out my grinding. Usually with 120.

 

[RIDE-RED 350r]

I'm really digging that idea of wider on top tapering to stock width on the bottom

 

[Stump Shot]

So.......what about finish?

Super shiny?

Sorta rough?

Why?

Oh Mastersohn, answering with questions... Well this is one area(and probably the only one) that I can add to the conversation. I personally am convinced that polishing a port does have not only merit but gains in HP. So I did talk a little about my baby steps approach to porting and this is one of the steps. I have done numerous exhaust ports just cleaning up the dingle berry's left from casting and smoothing them out with a mini sanding drum then a green stone. This mind you with no other modifications to the saw to muddle things up. Now I don't have a dino to prove all this, all I can say is there is more vim and vigor in the engine that I can hear, see and feel. Here's what I learned from the old timers over the years on the why part of it. The exhaust port is special in that it is not just about flow, like the other ports are that have a fuel/air mixture in them. The exhaust has a flame front, look at the habadda habadda saw to see it. So it doesn't take much work to get it to not disrupt the flame coming out, so why go any farther than this? I mentioned taking off the casting imperfections as being important in the fact that they pick up heat, a lot of heat, which in turn is transferred right back into the cylinder. So think of the rough sanding in the port like little fins that are picking up heat, if we can eliminate these, the cylinder will be cooler. I believe this is more important in the work saw than in the race saw for obvious reasons. Also carbon has a much, much tougher of a time trying to adhere to a smooth port versus a rough one, also a big benefit to a work saw. How shiny? Well maybe there is some room for debate after all, the ones I do won't refract light and look at home on the front of a '57 Buick Road Master. They are smooth and seem satisfactory to me. I can not see any problem with going further and making it like a mirror finish, I'm just not sure of the need and or gain here.
Again, this is for just the exhaust port. Most of this goes back to my teachings from the ones before me. None of this is anything new or unknown by any means.
This modification, while slight is very easy for a beginner like myself to do without worry of ruination, it is not however porting a saw, rather a part of that process. Like I mentioned before it is taking what is already there and perfecting it. Engine builders call this blueprinting an engine and it does pay off in power.

 

[Stihlbro]

I'm trying to add something here, but I can't keep up. The overall shape of the port is a direct reflect of the life of the piston and rings. It also can be a determining factor on somewhat power output. I like to keep what the factory has on what I consider a work saw. I like everyone else did the mirror finish on the exhaust port, agree that after moderate use the port accumulated carbon build up.

 

[Mastermind]

That can be a good thing. Less heat absorbed the better. 288 rattler Mike did.

That pic leads me to another question.

Angle of the floor?

Steep downward angle?

Relief step?

Thoughts?

 

[EvilRoySlade]

This is what I prefer for angles. Even steeper if materials could handle the stress.

 

[drf256]

This is what I prefer for angles. Even steeper if materials could handle the stress.

Youre drawing a Husky 262 Jug.