Part Two: The Intake Port

[huskyboy]

What shape intake runs best for you guys?

 

[Mastermind]

What shape intake runs best for you guys?

Intake shaped.

Errabody knows dat.

 

[huskyboy]

Intake shaped.

Errabody knows dat.

I thought Mickey mouse shaped was supposed to be the best? I heard it on utoob. Lol

 

[huskyboy]

One of the better running saws I did has a intake that looks like this. Food for thought.

 

[Ketchup]

I like wide.

 

[huskyboy]

288

 

[Terry Syd]

OMG!

No doubt it was advertised as being 'ported'....

 

[huskyboy]

OMG!

No doubt it was advertised as being 'ported'....

That’s the way it came factory. Pretty ugly lol.

 

[Powerstroke Cowboy]

Hello all,

I am new to this forum. First off thanks for having me. I joined because of the porting series Mastermind has put together. I have been enjoying reading all the discussions on the subject of porting a chainsaw. I have learned a lot of valuable information. Thank you all!!

I hope I am not out of line in bumping this thread. If I am I apologize and please let me know so I don't make the same mistake twice.

Now, on to the question. While reading through this thread on intake porting,the subject of port duration keeps being brought up. I agree that to much duration is a bad thing, being most times it gained by changing port timing. That in turn affects spit back and lowers the crank pressure if took to far.

My question is, what about duration gained by raising the roof of the port? I can't see how this would be a detrimental way of gaining duration. That is as long as you have room between the roof of the port and piston skirt at TDC. And if itdoes not affect the rings/piston does not go lower than the roof at BDC?

Is this thinking correct? Or am I all wet?

I am looking at it like a higher duration cam, more duration is fine as long as the valve still closes in time.

Thanks!

 

[farminkarman]

Hello all,

I am new to this forum. First off thanks for having me. I joined because of the porting series Mastermind has put together. I have been enjoying reading all the discussions on the subject of porting a chainsaw. I have learned a lot of valuable information. Thank you all!!

I hope I am not out of line in bumping this thread. If I am I apologize and please let me know so I don't make the same mistake twice.

Now, on to the question. While reading through this thread on intake porting,the subject of port duration keeps being brought up. I agree that to much duration is a bad thing, being most times it gained by changing port timing. That in turn affects spit back and lowers the crank pressure if took to far.

My question is, what about duration gained by raising the roof of the port? I can't see how this would be a detrimental way of gaining duration. That is as long as you have room between the roof of the port and piston skirt at TDC. And if itdoes not affect the rings/piston does not go lower than the roof at BDC?

Is this thinking correct? Or am I all wet?

I am looking at it like a higher duration cam, more duration is fine as long as the valve still closes in time.

Thanks!

You don't gain intake duration by raising the intake roof....you can increase port volume by doing it, which may or may not be a good thing.

 

[huskihl]

Hello all,

I am new to this forum. First off thanks for having me. I joined because of the porting series Mastermind has put together. I have been enjoying reading all the discussions on the subject of porting a chainsaw. I have learned a lot of valuable information. Thank you all!!

I hope I am not out of line in bumping this thread. If I am I apologize and please let me know so I don't make the same mistake twice.

Now, on to the question. While reading through this thread on intake porting,the subject of port duration keeps being brought up. I agree that to much duration is a bad thing, being most times it gained by changing port timing. That in turn affects spit back and lowers the crank pressure if took to far.

My question is, what about duration gained by raising the roof of the port? I can't see how this would be a detrimental way of gaining duration. That is as long as you have room between the roof of the port and piston skirt at TDC. And if itdoes not affect the rings/piston does not go lower than the roof at BDC?

Is this thinking correct? Or am I all wet?

I am looking at it like a higher duration cam, more duration is fine as long as the valve still closes in time.

Thanks!

There is no duration measured at the intake roof. It’s measured from the time the skirt opens on the floor until it closes on the floor. What you are primarily concerned about is the area of the port at the carburetor, outside of the flange, and at the plating

 

[Powerstroke Cowboy]

There is no duration measured at the intake roof. It’s measured from the time the skirt opens on the floor until it closes on the floor. What you are primarily concerned about is the area of the port at the carburetor, outside of the flange, and at the plating

You don't gain intake duration by raising the intake roof....you can increase port volume by doing it, which may or may not be a good thing.

Thank you. As you can see, I was confused. I somehow spaced the fact that duration is measured on a saw in open to close. I think I got duration and lift, confused.

Typical noob at it's finest. LOL!

 

[huskihl]

Thank you. As you can see, I was confused. I somehow spaced the fact that duration is measured on a saw in open to close. I think I got duration and lift, confused.

Typical noob at it's finest. LOL!

Yep there is no “lift”.

More area can potentially flow more if there’s enough vacuum to pull it, but it will lose velocity and potentially get lazy

 

[Powerstroke Cowboy]

Yep there is no “lift”.

More area can potentially flow more if there’s enough vacuum to pull it, but it will lose velocity and potentially get lazy

Yea. I need to quit thinking like a 4-stroke.

I see what you are saying. It make sense as well. On that note. How important is it to keep the port as close to the same size as the bore on the carb?

 

[huskihl]

Yea. I need to quit thinking like a 4-stroke.

I see what you are saying. It make sense as well. On that note. How important is to keep the port as close to the same size as the bore on the carb?

It’s more important that nothing is wavy. Like an accordion

 

[Mastermind]

Most of the stuff we (us old farts who have done this a long time) have learned on each model has been from testing different durations, areas, etc. What makes one model haul ass might turn another into a turd. Best bet for a noob....ask questions related to an individual model. Most of us will share what we've figured out. Keep in mind that there are many ways to skin a cat.....so the replies might vary. But that does not mean they are wrong. Clear as mud? LOL

 

[Powerstroke Cowboy]

Most of the stuff we (us old farts who have done this a long time) have learned on each model has been from testing different durations, areas, etc. What makes one model haul ass might turn another into a turd. Best bet for a noob....ask questions related to an individual model. Most of us will share what we've figured out. Keep in mind that there are many ways to skin a cat.....so the replies might vary. But that does not mean they are wrong. Clear as mud? LOL

I appreciate that yall are willing to share your knowledge on the subject at hand. That's what drew me to this forum. I understand what you are saying about each model being different. Clear as a mountain lake. LOL.

The saw I am working on is a clone MS880.

 

[Mastermind]

I appreciate that yall are willing to share your knowledge on the subject at hand. That's what drew me to this forum. I understand what you are saying about each model being different. Clear as a mountain lake. LOL.

The saw I am working on is a clone MS880.

Just port work....or machine work too? Makes a difference. I do machine work to lower the exhaust port on an 880 for a work saw. On race saws.....I'm no help.

 

[Powerstroke Cowboy]

Just port work....or machine work too? Makes a difference. I do machine work to lower the exhaust port on an 880 for a work saw. On race saws.....I'm no help.

Both, I have already cut .032 of the base to tighten up the squish. I have no way of going in the cylinder and cutting the squish band. So I can only go so far.

All I am looking for is a good running work saw. The most it might see is a 42" bar.

 

[Mastermind]

Both, I have already cut .032 of the base to tighten up the squish. I have no way of going in the cylinder and cutting the squish band. So I can only go so far.

All I am looking for is a good running work saw. The most it might see is a 42" bar.

What are the port timing numbers now?