Wanna Talk About Port Shapes?

How is the modification to the transfers determined? The intake and exhaust seem logical but the transfers have me confused. Like on the 064 why does the finger port start offset and jog across, as opposed to say centered between upper & lower?

Thanks for taking the time to do this.

 

If you want to see it? I have pics of a 166 ported work saw exhaust to compare to squared exhaust for race 166. It's amazing the difference.

 

Finger ports and bridge ports just add transfer area. No real rhyme or reason to their shape. The idea is to just add a bit more.

Dex.......not many of the saws I do get finger ports......but I put the bridge ports in a lot of two port engines.

 

On that 460 cylinder it looks like the finger ports might compete with the intake for space, so you have to decide whether a finger port or an enlarged intake is more valuable. How do you balance that? Is there a minimum cross-sectional size for finger ports, below which they just have too much wall surface area relative to cross sectional area to be worthwhile?

Since the total volume of fuel mixture that makes its way through on each stroke can't be more than the displacement no matter what you do with the ports, there must be diminishing returns as you add port area. When is enough enough?

 

Send it to someone or leave it stock!

 

Leave it stock? Hahaha come on man.

 

No, to port the jug.

 

Oh yeah, I dont mess with the jugs, just every muffler that comes in.

 

I'm sure you are right here.

And we are veering off into race saw country.

For gas powered work saw finger ports are rarely used, by me at least. I do add the bridged ports on quite a few two port engines, and I see those engines holding RPM in the cut a little better because of them.

If we continue to add transfer area......we would soon need more carb. Then a tuned pipe.......and even more carb.......then some nitromethane.

 

You are too modest.....everyone here knows you are da man when it comes to work porting saws....

 

I've not done bridge ports like those. Just true fingers on a couple saws. I may try a set of those or fingers that connect with the uppers on one of these cylinders.

 

I just try hard to be consistent......no tricks or secrets.

Mike they help the saw hold RPM in the cut a little better.....not a huge gain.....but for the small amount of time it takes to do em......they are worth it to me.

 

I don't mind doing them at all. I just don't want to get a knock for copyright infringement with CT13

 

You set them close to the transfer timing is depending on what you're trying to accomplish.

 

Like Mike said.......the height of the finger ports, like all transfer ports, is measured and set carefully. On this 064 the transfer ports open at 118 degree ATDC.

 

For the couple guys wanting to see work v/s race porting in a 166. The race 166 was ported by top name way ahead of his time in his late 80's now and still copied today. Marcel Vincent.