Why an engine makes more power off a burr finish

[user-9274568]

It sounds like the difference depends on how good or bad the port or manifold is before texturing.

That's not it. How fast or slow or close to average air speed it needs to be.

[900HP]

It isn't really fair to say that rough ports do not work because some people don't use them.

1. It is a lot of unpleasant, difficult, work to make them rough.
2. Human nature makes us want things that are smooth and shiny.

There are some people/companies that go to great lengths to get a textured surface. Personally I feel it's application specific (isn't everything) but my thoughts are the lower the rpm you run at the more important boundry layer management becomes. My personal belief is that it helps to reduce "wall wetting" and keeps a better mixture. (of course, I also believe in mirror polished exhaust ports too so there you have it)

rottler dimple finish.jpg

[289nate]

It sounds like the difference depends on how good or bad the port or manifold is before texturing.

That's not it. How fast or slow or close to average air speed it needs to be.

Thanks for the clarification.

[dirtmod87]

I had Chad burr finish a set of my 18* Northeast Big Block Dirt Modified heads for me.. He did the intake runners and the chambers. I also have an identical set non burr finish. On the dyno both, engines are very close, 842 without to 850 with burr finish. On the track I can tell you the burr finish combo pulls noticeably harder off the corner, I wish we had done the intake also.. Just my experience. I think there is something there, but it's sometimes difficult for a head guy to send something out without it being shiny and smooth or the customer thinks he's getting ripped off.. JMO

[user-9274568]

I had Chad burr finish a set of my 18* Northeast Big Block Dirt Modified heads for me.. He did the intake runners and the chambers. I also have an identical set non burr finish. On the dyno both, engines are very close, 842 without to 850 with burr finish. On the track I can tell you the burr finish combo pulls noticeably harder off the corner, I wish we had done the intake also.. Just my experience. I think there is something there, but it's sometimes difficult for a head guy to send something out without it being shiny and smooth or the customer thinks he's getting ripped off.. JMO

And this is all that matters! You can debate until the World's End and this is all the data you need..

Here is your chamber BTW!

[cv67]

that rottler finish how the heck did he do that?

[The Radius Kid]

From what I've been able to gather so far:

A properly designed port may or may not show much improvement with texturing if used over a narrow operating band,port velocity taking care of things.
If,however the engine sees significant changes in RPM while it's operating,this will probably show improvements.
Is that about right?

[user-9274568]

From what I've been able to gather so far:

A properly designed port may or may not show much improvement with texturing if used over a narrow operating band,port velocity taking care of things.
If,however the engine sees significant changes in RPM while it's operating,this will probably show improvements.
Is that about right?

This makes it sound like a crutch. I view it more as a tuning aid.

[T-flow]

From MPE, Some area's will benefit with a rough texture and some area's will have little effect. But is there something to be had, sure!
There is a lot going on in an Intake manifold thats carrying fuel.

[The Radius Kid]

From what I've been able to gather so far:

A properly designed port may or may not show much improvement with texturing if used over a narrow operating band,port velocity taking care of things.
If,however the engine sees significant changes in RPM while it's operating,this will probably show improvements.
Is that about right?

This makes it sound like a crutch. I view it more as a tuning aid.

Actually,I'm with you on this.
There's been a lot of work in airflow testing using textured finishes to enhance flow.
I think back to what Smokey Yunick said about different competitor's engine combos that didn't look like they'd work,but actually went very well.
Sometimes things aren't always as they would seem to be.

[Warp Speed]

It sounds like the difference depends on how good or bad the port or manifold is before texturing.

[69434]

Gross texturing, is usually aerodynamically bad. The proof is more than 100 years known and infinitely confirmed. Moreover, this discussion has been repeated from time to time and is always answered by the practices of those with the greatest ability to find the truth. They use smooth textures, sometimes polished or satin or mat. But, I have heard of them using fine roughness in spots -to delay flow separation at points of difficult curvature. Not gross textures and never the whole port.

Atomization is always important. It is the job of the carbs or injectors. If they do their job right, the mixture condition will be more than adequate to burn and can be optimized by the engine tuner. The fuel wetting the walls of the port that does not get burned is insignificant except for emissions. It is not worth doing anything to the port, that costs flow energy, just to scrub fuel off the walls. And, the high buck builders do not texture walls to lift fuel off.

Very well said...

[Larry Widmer]

A rough finish port delivers a slightly cooler mixture to the cylinder than a slick one......

[140Air]

A rough finish port delivers a slightly cooler mixture to the cylinder than a slick one......

How did you measure this?

[289nate]

From what I've been able to gather so far:
This makes it sound like a crutch. I view it more as a tuning aid.

[/quote]

What I initially meant was there is only so much a porter can do with different castings. It may be a very beneficial tuning aid do to the design of the port a porter has to work around. Not because of the skill of the person porting the head. But, because of the compromised design of the port being worked on.