Porting 101

[TraditionalTool]

starting the exhaust

I started opening up the exhaust.

Comments appreciated. Seems I should even it out just a tad more, and still need to work the inside a bit, I took the sides out just a tad but can widen a tad more. Here's a pic of the outside. The inside came out blurry...

Here's the intake that I started.

 

[TraditionalTool]

What about the back of the muffler?

Do you open up the back of the muffler more so that it can get the exhaust out easier?

 

[TraditionalTool]

Progress pics...

Comments appreciated.

NOTE: I didn't do a lot of measuring, other than measuring the length of the tape to be 70 percent of the diameter. I didn't do too much marking either, but did some. I tried to err on the safe side.

I have a stone also, maybe I should use it?

intake:

exhaust:

intake:

exhaust:

 

[AUSSIE1]

When you look at your ports at the cyl, try and make them reasonably square at the sides. In the corners you are losing some port area, if you get my drift. You don't need an oval port.

Your port, whether inlet or exhaust, from the cyl to the outside should be straight, no curvature.

Open up the muffler to the outer specs of your port.

I use the base gasket as a template.
Check your cases with the base gasket. If the gasket is a good match against the cases, you use this to match your transfers to the gasket/cases.
If you have to blend the transfers in, you don't have to go deep, just nice flowing lines.

Your doing a good job.
Keep at it.

 

[edisto]

This is a good number to know, and gives a second point of reference.

If/when you start doing some serious experimentation with porting, you are going to want to know area and time/area, and for those you need to work with the actual port widths.

When you look at your ports at the cyl, try and make them reasonably square at the sides. In the corners you are losing some port area, if you get my drift. You don't need an oval port.

Losing area, yes, but flow should poor through a square port because of the dead space in the corners where the 2 boundary layers meet.

Also, the wider the port gets, the more of a beating the rings take, because they extend farther into the port, and so the oval shape eases them back in.

 

[TraditionalTool]

When you look at your ports at the cyl, try and make them reasonably square at the sides. In the corners you are losing some port area, if you get my drift. You don't need an oval port.

Yeah, I went back and pulled the corners up some, to try and get that funnel shape, but it's still not ideal.

I used a silicon carbide grinding bit (dremel, small green) and it was working ok for a bit, but then I noticed that there is no more stone left....I have a couple aluminum oxide stones also. I haven't tried those yet.

Your port, whether inlet or exhaust, from the cyl to the outside should be straight, no curvature.

The intake was better than the exhaust in that regard, but I cleaned up the exhaust also, a bit more.

Open up the muffler to the outer specs of your port.

Right now it is pretty close to a match. I traced it out on paper to make sure.

I use the base gasket as a template.
Check your cases with the base gasket. If the gasket is a good match against the cases, you use this to match your transfers to the gasket/cases.
If you have to blend the transfers in, you don't have to go deep, just nice flowing lines.

I'm not gonna mess with the transfers at all. I don't think I'm gonna do too much more to it. But I will try to flatten the sides up any more that I can.

I need to bevel the roof of the ports on the cylinder side still.

Thanks for the encouragement!

 

[TraditionalTool]

Losing area, yes, but flow should poor through a square port because of the dead space in the corners where the 2 boundary layers meet.

I think I know what he meant, about the side being straight, rather than square. I tried to soften those corners so that air would flow.

Also, the wider the port gets, the more of a beating the rings take, because they extend farther into the port, and so the oval shape eases them back in.

I was thinking that looking at it the first time. While a funnel shape is ideal, it seems that if the roof comes down at the corners, it's safer for the rings.

I think that is what your describing with the oval ends.

 

[AUSSIE1]

Roof and floors catch rings, you only need a slight curvature here.
Your sides can be reasonably square with a radius in the corners.
Bevel roof and floors.
Clean up sides being careful not too take to much off.
If you take your sides out to your measurements, beveling here too much will only add to your dimensions.

 

[AUSSIE1]

Stones clog up too easily.
Tungsten carbides are best.
Someone mentioned a wood rasp, files even.
A chainsaw file to finish off.
If you use a file, fit some hose to the end so there's no possibility to damage the bore.

 

[sawinredneck]

Looking good TT I'd smooth the transition on the exhaust side a little more, leading to the muffler, and smooth it out a bit, looks like there are some humps here and there. When running the Dremel think of it as "petting" rather than grinding and see how that works for you.
Some guys like to polish them to a mirror finish, I don't much see the need myself, expecially on the intake side.
I would encourage you to at least smooth the transfers, knocking off the flashing etc. before you put it together. Then if you want to measure gains you can port them later.

 

[TraditionalTool]

Looking good TT I'd smooth the transition on the exhaust side a little more, leading to the muffler, and smooth it out a bit, looks like there are some humps here and there. When running the Dremel think of it as "petting" rather than grinding and see how that works for you.

I did clean things up last night and funny you mention "petting", as I think I was doing more of that. At first I used a carbide burr bit, the small cone shaped one up in the thread...switched to a green silicon carbide stone and was smoothing things out, until I noticed the stone was pretty much gone... Then I used an alu oxide similar and it was holding up better and I could smooth things out some.

Some guys like to polish them to a mirror finish, I don't much see the need myself, expecially on the intake side.
I would encourage you to at least smooth the transfers, knocking off the flashing etc. before you put it together. Then if you want to measure gains you can port them later.

I don't see any flashing around them. Are you just talking about the corners?

Also, what do you use to put a bevel on the roof/floor of the ports? Hard to get the dremel at that angle, so I was gonna try some small files and/or bend a triangular handsaw file so that I can reach back in and hook over the cylinder wall. I know it only needs to be slightly radius'd over.

 

[blsnelling]

Also, what do you use to put a bevel on the roof/floor of the ports? Hard to get the dremel at that angle, so I was gonna try some small files and/or bend a triangular handsaw file so that I can reach back in and hook over the cylinder wall. I know it only needs to be slightly radius'd over.

Don't worry about the transfers for now on your first port job.

I use a round stone to bevel the ports. If you don't have one, you can make one by shaping it with the "stuff" you use to dress your chain grinding wheels. I suppose you could grind on concrete a while if you don't have that, lol.

 

[TraditionalTool]

Don't worry about the transfers for now on your first port job.

I'm not going to.

I use a round stone to bevel the ports. If you don't have one, you can make one by shaping it with the "stuff" you use to dress your chain grinding wheels. I suppose you could grind on concrete a while if you don't have that, lol.

I had some grinding wheels that are too big for the dremel, but you know what they say...if you got big stones, flaunt 'em!

I just used them and abraded the edge to soften it, by hand. You just put a slight bevel on the edge, right?

 

[blsnelling]

I'm not going to.

I had some grinding wheels that are too big for the dremel, but you know what they say...if you got big stones, flaunt 'em!

I just used them and abraded the edge to soften it, by hand. You just put a slight bevel on the edge, right?

You don't need to worry much about the sides, just the top and bottom. You should only need to bevel where you widened it since you didn't raise or lower the ports. Just extend the bevels that are already in the center.

 

[TraditionalTool]

You don't need to worry much about the sides, just the top and bottom. You should only need to bevel where you widened it since you didn't raise or lower the ports. Just extend the bevels that are already in the center.

Brad,

Wouldn't the center of the roof be the most likely place that the ring would catch in this situation though? As you widen it, seems that exposing more of the ring would present the most danger at the center of the radius.

 

[TraditionalTool]

Unfortunately I got stuck at the DMV with my son, getting him an ID card. Tomorrow morning I need to drive home to college, so won't get to this and get it together until I get back, Sun./Mon. most likely. Will post progress pics when I do.

 

[edisto]

Brad,

Wouldn't the center of the roof be the most likely place that the ring would catch in this situation though? As you widen it, seems that exposing more of the ring would present the most danger at the center of the radius.

If the roof is curved, then when you hit the "stock" part of the roof, that curve should already have eased the ring back into the cylinder a fair amount.

 

[blsnelling]

Brad,

Wouldn't the center of the roof be the most likely place that the ring would catch in this situation though? As you widen it, seems that exposing more of the ring would present the most danger at the center of the radius.

That is correct. Theoretically, you need the most bevel in the center. The flatter the port is, the more that is true.

 

[TraditionalTool]

If the roof is curved, then when you hit the "stock" part of the roof, that curve should already have eased the ring back into the cylinder a fair amount.

Ah, this makes sense. As the sides raise, the area of the ring which becomes supported is greater in that sense.

That is correct. Theoretically, you need the most bevel in the center. The flatter the port is, the more that is true.

Yes, this also does make sense.

I just got home, long trip to L.A., but will get to play with my 350 tomorrow.

Thanks for the help, both of you and redneck too (even pepsifreak for starting this thread.

 

[pepsifreak28]

Thanks TT I have been watching the thread, been busy myself this past week end with a helping with a pig roast yummie...

Lots of good expert advice from many I hope it keeps going with more pictures and can make a reference to bl's thread and this one on porting from start to finish keep the pictures coming