Wanna Talk About Port Shapes?

[Mastermind]

I rarely widen the port much........normally I just reshape it.

 

[Terry Syd]

Terry that's what I see with the bridge ports too.....more of a change in flow direction than volume. If a straight, or flat roofed transfer is best for peak power, and a angled one increases range, then these bridge ports may help to widen the range of peak power.

And I would bet that with a dyno available, one of your projects would be to see how wide and deep those channels need to be to get the effect you want...

 

[hillwilliam]

Thanks Randy! You share a lot of knowledge, and it's always appreciated.

 

[Bieber]

If i have the upper transfers angled like in a ms460 jug, is it recommendable to level them so that front and back of them open simultaneously? Or would this result in a flow decrease?

 

[Mastermind]

That is how I end up. Front and back opening at the same time.

 

[Bieber]

Thank you Mastermind!

I'm grinding on my 440/460 hybrid project right now
and I'm scared of having the upper corners of the exhaust done a bit too tight...!?
your opinion...
this is the Mahle 460 jug:


just for comparison an older 034S jug from Kolbenschmidt:
was suprised of these tight edges and flat roof...

 

[Mastermind]

You are just fine.

Watch the floor of the exhaust.......be careful not to lower it.

 

[Bieber]

You are just fine.

Watch the floor of the exhaust.......be careful not to lower it.

Thank you Sir!
I though raised the exhaust by 1-1.5° just to smooth it out a little more and now I'm at 101° atdc.

 

[Magnum783]

Ok I am intrigued as they get about this port shape ordeal. I have access to a mill and lathe so porting work is not a huge stretch. I work for the Department of defense as the foreman of a job shop. I am putting a new cylinder and piston on my ms260 and would like to open up the intake and exhaust just a bit. I don't know a whole lot about this so I am reaching out to the pro's. I have ported and polished many small block chevy engines and have worked as a mechanic part time or years so I understand the concepts of what you guys are doing just looking or details. I am also not looking to do a full port that takes far more education than I poses at this time just looking to open the intake and exhaust up a bit as I live at 6200 feet and we loose a bunch of power up here due to altitude just trying to make some of that up. Pics or advice appriciated.

 

[mdavlee]

Compression will be your friend at 6200'.

 

[weimedog]

Just want to say thank you yet again for sharing some of your experience. Looks to me like the connected porting concept you show here is a way to get a little more towards the intake side of the combustion chamber. Two things cross my mind when I saw this thread.... one. Looks like a way to push my 2094 to the next level, could be FUN ... that saw is a test hog that is both a beast and fun. Two; this might be a way to move the 272's a step closed to the quad port designs.

Was thinking of trying finger ports on some of those older single open port saws just for chits & grins. Maybe on saws like 51-55 Huskys as well. A way to bring them into the realm of the newer designs?

Still wondering about having differential heights on the quad port saws where the intake side opens at some point before. Or even having a top edge cut on the two port designs to favor the intake side. Saw this in other worlds and wonder if it translates here. I'm a fan of bearing surface for heat transfer. So if there is a way get similar results without reducing bearing surfaces for the piston (Cylinder wall) I'm going to try it. In the same spirit of dropping intake ports vs. widening them to use timing to effectively get the same thing... just thinking in text.. just wondering... think I asked this before once. Might be time to just hack and see. You ever see anything along those lines?

 

[Mastermind]

Compression increase will give you the best gains.

 

[kz1000]

If I send you some of the tools that are required to port my saw, will you give me a discount??? I have several pencils and a box of business cards from a closed Pizza joint already boxed.

 

[redfin]

Randy, I faintly recall seeing you post what burs you use in your handpiece and I thought they were in this thread? But I must be mistaken. Would you post these again please?

 

[Magnum783]

So how do I gain compression? in car world we do that by dropping the deck? In a saw that would mean lowering the cylinder height correct? I had already planned on taking out the base gasket and replacing it with gasket maker. I just am un sure if I need to lathe any off the bottom of the cylinder. Does cleaning up the intake or exhaust help the cause in any way?

 

[weimedog]

Compression increase will give you the best gains.

Yup.. hoping to have the Lathe set up before winter.

 

[Mastermind]

So how do I gain compression? in car world we do that by dropping the deck? In a saw that would mean lowering the cylinder height correct? I had already planned on taking out the base gasket and replacing it with gasket maker. I just am un sure if I need to lathe any off the bottom of the cylinder. Does cleaning up the intake or exhaust help the cause in any way?

I cut the area around the combustion chamber (cutting the squish band) and then the base to lower the jug, and decrease the size of the combustion chamber.

If the port timing numbers are in the right places......then widening (and cleaning up) the ports does little, if anything to gain power.

Remembering that there is very little time for the air/fuel/exhaust to move per stroke at 10,000 rpm, so keeping flow velocity high is far more important than increasing flow volume. At least in my humble opinion.

 

[weimedog]

If the port timing numbers are in the right places......then widening (and cleaning up) the ports does little, if anything to gain power.

I agree... the race guys looking for tenth's chasing those extra split seconds might find it worth time to work those ports. The rest of us hacks? Compression, muffler mods, port timing, AND a SHARP chain will be where the most useful gains are made. Assuming the rest of the basics are squared away. That's my humble opinion as a "hack".

 

[Magnum783]

I think my prob is my lack term knowledge. This squish band? Where is this elusive guy? I understand lower the base of the jug, I can easily do that on the 4jaw with an adapter plate such as you have. The squish band I have no idea where to look or how to adjust this thing.

 

[redfin]

Squish band is the bottom edge of the combustion chamber.