I had my intake manifold coated by Swain Technology ( http://www.swaintech.com/store.asp?pid=10961 ). I used their BBE heat emitting coating on the top and their TBC thermal barrier coating on the bottom surface. I don't have any before and after data to report, but they did do a good job, and the black manifold looks pretty good with the polished fuel rails.

 

Yep, that was helpful… first you tell me my response is totally wrong, then you repeat it and then make another BS statement…

Nutshell… if there is air/fuel flowing through it, generally some texture helps, usually in the curves and areas where the fuel would drop out of suspension if you didn’t create some boundary layer turbulence, otherwise there is an advantage to a smooth surface. Most turbulence, boundary layer or not causes the ports to act smaller (many significant areas of turbulence might as well be part of the port wall), unless there is some deficiency in the port shape (like it’s cast with a port floor that could really stand some filling) and making part of the port dead would help flow, gm actually did this OEM in some cases where they had crappy port entry angles between the heads and the intake.

Secondly, texture to the port walls allows the a/f charge to pick up more heat, this is especially useful for the MPG freaks out there that have found that exaggerating texture in the intake ports can actually impart enough heat to the a/f charge to have a similar effect on gas mileage as heating your fuel and air mixture (and also a similar effect at higher rpms, counterproductive to our MPG discussion).

As far as getting back shiny ports from a porter… it depends on where and when. The fact is a lot do it when it won’t hurt because the normal customer expects it. And in a lot of cases market expectations result in customer’s porting work looking different then what stays in the shop. I’ve seen things all shined and polished up with dimples formed in sections to prevent a/f separation.

 

If ya are referring to me then ya are incorrect about mirror polished ports and that is what I call smooth.
I have had more than one set ported and haven't seen mirror polished ports since the '60's.I have had head work done by some of the best too. They don't ask what type of intake ya are running whether it be Hilborns,Carb,EFI or Blower. They port them correctly.
If mirror polishing had ANY advantage there would be a LOT of it being done,which there isn't.
Haven't seen many ports that didn't flow fuel unless ya got a sprint car set up that is direct cyl injected where the injector is next to the spark plug.

I will quote again from the porting article I posted:
"A common beginning porter’s mistake is to apply a nice, shiny finish to all ported surfaces. If your heads come back this way from a tuner, expect less, not more power!"
So there ya have it.

 

So if you have a direct injected motor then mirror finish ports would be acceptable (and potentially superior)?

 

The way I'm reading this is that portion of the "intake tract" that actually carries an air/fuel mixture should have a rough finish. If that statement is true than that part of the "intake tract" that does not carry an air/fuel mixture but just air would benefit from a smooth finish. That is exactly what I intend to do.

 

it is not possible (with todays technology) to develop a useable boundry layer on a perfectly smooth surface...DON'T COAT THE INSIDE OF YOUR INTAKE RUNNER!

Just the right amount of heat in the intake runner will aid in vaporization...

it's just not as simple as these coating companies make it sound...

 

And there ya have it from another expert.