What is Porting Polishing

[bondvagabond]

Originally Posted by Frank Lee

That's for "wet" manifolds; carb'd or throttle bodied with fuel and air flowing through. Most anything newer is port injected and the manifold runs "dry". Don't know what prevailing theory is on intake smoothness but I'd think the smoother the better.

Exactly, that is why I said "on carb and Tbi engines".

a great example of this is the ford "Lima" engine (found in rangers)that went from carb all the way to multiport injection, without a ton of non fuel delivery engine changes. These motors are know for best in class mpg in small trucks, and once they went to mpi the intake runners got smoother.

[bondvagabond]

Originally Posted by Iexpedite

I would have liked to have seen those headers. I'm guessing they were long tube if you were trying to maximize scavenging.

I sold it to a buddy who is a not super active forum member, can't remember her ecomodder name, has a bunch of z's in it, will text her and see if she can pm you a pic.

Let's put it this way, I don't have my notes with me, but am getting ready to weld up a set for my 7.3 diesel and the interior runner diameter is like 0.6xx"
So the geo was tiiiiiny

[niky]

Originally Posted by Frank Lee

That's for "wet" manifolds; carb'd or throttle bodied with fuel and air flowing through. Most anything newer is port injected and the manifold runs "dry". Don't know what prevailing theory is on intake smoothness but I'd think the smoother the better.

Back in the 00's, Mazda used a variable " tumble/swirl " mechanism to increase turbulence in the intake port at low rpm and idle, to go along with their variable length intake runners.

[freebeard]

Originally Posted by bondvagabond

I welded up a set of headers for a geo metro optimizing for this scavenging effect, one of the real engineers one here helped me calculate size and length. The runners were TINY! As in, they don't sell exhaust tubing that small. Torque and fe both increased. This custom header was essentially the opposite of porting.

You're throwing red meat in front of the Metro owners here (I'm not one). What are you prepared to put up? Pictures or dimensions?

I think a lot is being 'left on the table'. Anywhere in nature you have a branch in a tube with a flowing fluid, from blood vessels to Oak tree branches, the primary swells and then transitions into the fork. Someone should pit 3D printed test manifolds designed by a genetic algorithm against each other, steered by real-world testing. Hydro-forming for the finished product.

Insofar as the rough/smooth part, I recall a theory where the inside of a curve is rough and the outside smooth, or vice versa. A student of Viktor Shauberger would suggest spiral grooves. Apparently rivers fold over as they go around bends.

I remembered: With flathead Fords it was Porting and Relieving. That was reshaping the part of the combustion chamber cast into the block. And porting also includes reshaping the valve guide area on a pushrod engine.

[some_other_dave]

Since the valve guides typically extend into the port, re-shaping the guides is technically part of porting most engines. I've seen some that not only cut the guides down, but gave the port wall around the guide a nice airfoil shape to help flow around the remaining bit of the guide and the valve stem.

Heck, if we didn't need the valves to rotate (in order to move any hot spots around and even out any wear) we could have the stems be airfoil-shaped and get even better flow that way.

But again, that's primarily of help in high-flow situations. Which are found at high RPM, which is the opposite of where we drive.

-soD